Manual For Hybrid Rice Seed Production 272p7

The International Rice Research Institute (IRRI) was established in 1960 by the Ford and Rockefeller Foundations with the help and approval of the Government of the Philippines. Today IRRI is one of 18 nonprofit international research centers ed by the Consultative Group on International Agricultural Research (CGIAR).The CGIAR is sponsored by the Food and Agriculture Organization of the United Nations (FAO), the International Bank for Reconstruction and Development (World Bank), and the United Nations Development Programme (UNDP). Its hip comprises donor countries, international and regional organizations, and private foundations. IRRI receives , through the CGIAR, from a number of donors including FAO, UNDP, World Bank, European Economic Community, Asian Development Bank, Rockefeller Foundation, Ford Foundation, and the international aid agencies of the following governments: Australia, Belgium, Canada, People's Republic of China, Denmark, Finland, , , India, Islamic Republic of Iran, Italy, Japan, Republic of Korea, The Netherlands, Norway, Philippines, Spain, Sweden, Switzerland, United Kingdom, and United States. The responsibility for this publication rests with the International Rice Research Institute. Copyright ª International Rice Research Institute 1993. All rights reserved. Except for quotations of short ages for the purpose of criticism and review, no part of this publication may be reproduced, stored in retrieval systems, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission of IRRI. This permission will not be unreasonably withheld for use for noncommercial purposes. IRRI does not require payment for the noncommercial use of its published works, and hopes that this copyright declaration will not diminish the bona fide use of its research findings in agricultural research and development. The designations employed in the presentation of the material in this publication donot imply the expression of any opinion whatsoever on the part of IRRI concerning the legal status of any country, territory, city, or area, or of its authorities, or the delimitation of its frontiers or boundaries. Production of this publication was made possible through a grant from the Government of Italy to IRRI's Hybrid Rice Project. International Rice Research Institute P.O. Box 933,1099 Manila, Philippines FAX: (63-2) 818-2087, 522-4240 Electronic mail: IN%"[email protected]" Telex: (ITTI 40890 RICE PM (CWI) 14519 IRILB PS (RCA) 22456 IRI PH (CWI) 14861 IRI PS

ISBN 971-22-0045-0

Contents

FOREWORD DEDICATION THE RlCE SEED

1 The rice plant 1 The seed and the grain Parts of a seed 2

SYNCHRONIZATION OF FLOWERING

13 Differential seeding 13 How to determine seeding time of A and R 13 lines

HYBRID RlCE PARENTAL LINES

Transplanting the A line Transplanting the B line

23 29

2 DIFFERENTIAL SEEDING TIMES

REPRODUCTIVE PARTS OF THE RlCE PLANT

The spikelet 3 Process of seed formation Stages of seed formation Inbred rice seed 5 Hybrid rice seed 5

TRANSPLANTING SEQUENCE FOR CMS MULTIPLICATION 23

4 4

6

Male sterile line 6 Maintainer line 7 Restorer line 7

3

14 Differential seeding times for hybrid seed production 14 Seed parent has 10-day shorter growth duration than pollen parent 14 Seed parent has 10-day longer growth duration than pollen parent 15 Seed parent has same growth duration 15 as pollen parent Differential seeding times for CMS 16 multiplication

SELECTION OF CMS MULTIPLICATION AND HYBRID SEED PRODUCTION FIELDS

DESIRABLE CHARACTERISTICS OF PARENTAL LINES

8 Desirable characteristics of the CMS line 8 Desirable characteristics of maintainer 9 and restorer lines Choice of parents for hybrid seed production 9

SEEDING OF PARENTAL LINES IN THE SEEDBED 10

Why seed in the seedbed 10 Seedbed preparation 11 Pregerminating seeds 11 Managing the seedbed 12

17

Requirements 17 Distance isolation 17 Time isolation 18 Barrier isolation 18 TRANSPLANTING

Change the seedling proportion of R line 27 Seed the R line twice 28 Modify row ratios 29 Modify row and plant spacings Transplant R line seedlings on the same day 30

Why transplant 19 How to transplant 19 20 How many seedlings per hill Layout for transplanting 20 Seedling age at transplanting 20

What is a row ratio 21 Factors influencing row ratio 22 22 Characteristics of the R line 22 Characteristics of the A line Flowering behavior of the A and R lines 22

Seed parent has 10-day shorter growth duration than pollen parent 24 Transplanting the R line 24 Transplanting the A line 25 Seed parent has 10-day longer growth 25 duration than pollen parent Transplanting the A line 25 Transplanting the R line 25 Seed parent has same growth duration as pollen parent 26 Transplanting the R line 26 Transplanting the A line 26 SEEDING AND TRANSPLANTING MODIFICATIONS TO INCREASE SEED YIELD 27

19

TRANSPLANTING IN A SPECIFIC ROW RATIO

TRANSPLANTING SEQUENCE FOR HYBRID SEED PRODUCTION 24

21

29

MANAGEMENT OF SEED PRODUCTION PLOTS 31

Retransplant missing hills 31 Control weeds 32 Control diseases and insect pests Fertilizer management 33

32

34 Synchronization of flowering date of 34 parental lines Panicle initiation and flowering date 34 How to observe panicle initiation 35 Developmental stages of panicle 36 formation to flowering Estimating flowering date by panicle primordium stages 37 How to adjust flowering dates of parental lines showing 5-6 days difference at panicle initiation 37 How to adjust flowering dates of parental lines showing a difference of more than a week 37

ADJUSTING FLOWERING DATE

38 Crop stage for flag leaf clipping Flag leaf clipping method 39

FLAG LEAF CLIPPING

GIBBERELLIC ACID APPLICATION

Why spray gibberellic acid Timing of application—crop growth stage 40 Timing of application—weather conditions 41

40 40

38

How to make GA3 solution— general procedure 42 How to make GA3 solution—amount required for different plot sizes 43 How to make GA3 solution—doing your own computations 44 SUPPLEMENTARY POLLINATION

Methods of supplementary pollination 45 Timing of supplementary pollination 45

45

49 Special considerations for harvesting hybrid rice 49 When to harvest 49 Harvesting the B or R line 50 Harvesting the A line 51

HARVESTING

52 Preparation for threshing 52 Threshing the seed parent 53 Threshing the pollen parent 53

THRESHING

54 Why seed drying 54 Seed drying methods–sun-drying Seed drying methods–forced air drying 54

SEED DRYING

46 What is roguing and why is it necessary 46 Crop stage for roguing 46 Off-types to be removed 47 At maximum tillering 47 At flowering 48 Before harvest 48

ROGUING

PROCESSING HYBRID RICE SEED FOR. MARKET 55

Cleaning and grading 55 Seed germination testing 56 Packing and labeling the seed 57

54

Hybrid rice technology exploits the phenomenon of hybrid vigor and involves raising a commercial crop from F1 Seeds. This technology helped China to increase its rice production from 140 million tons in 1978 to 188 million tons in 1990. Research at IRRI and in other countries indicates that hybrid rice technology offers opportunities for increasing rice varietal yields by 15-20% beyond those achievable with improved, semidwarf, inbred varieties. Adoption and success of hybrid rice technology will depend largely on practical seed production technology; economical seed yields from hybrid rice plots; and efficient national seed production, processing, certification, and distribution programs in the public and private sectors. Hybrid rice seed production technology involves specialized skills and requires a

Klaus Lampe Director General

thorough understanding of various practices to minimize costs and maximize returns. This manual describes and illustrates the many steps involved in hybrid rice seed production for both beginning and experienced seed growers. It is based on experiments at IRRI and hybrid rice seed production experience in China. The authors have presented a complex topic in systematic, easy-to-understand that should appeal to trainers and growers alike. This book was edited by W.H. Smith with the assistance of T. Rola. The manual was designed for easy translation and inexpensive copublication in nonindustrialized countries, IRRI will give complimentary sets of the illustrations to cooperators who wish to translate the text and print local-language editions of the manual.

Dedication

This book is dedicated to the memory of my coauthor, Dr. H.L. Sharma, who worked with me at IRRI as research fellow during 19901992, on leave from Punjab Agricultural University, Ludhiana, Punjab, India. After his return to his parent institution, Dr. Sharma was named Head of the Department of Seed Technology. There he played an active role in developing and transferring hybrid rice seed production technology in India until his untimely death on 13 April 1993. Although Dr. Sharma did not live to see the publication of our book, the manual stands as a tribute to his contributions to hybrid rice seed production research and training at IRRl and in India. Sant Virmani

The rice seed

I

The rice plant The seed and the grain Parts of a seed

The rice plant A tiller is a shoot that includes the roots, stem, and leaves. It may or may not have a panicle. The panicle bears the spikelets. The spikelets are the parts of the rice plant that form seed.

Roots

Manual for hybrid rice seed production

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The seed and the grain Amature rice grain that germinates under favorable environmental conditions and grows into a normal plant is called a seed. A mature rice grain that may or may not germinate and is used for consumption is not a seed. Only seed can be sold to farmers to grow a rice crop.

Parts of a seed The embryo or germ gives rise to a seedling, which is composed of the shoot and the roots. The endospermis a food reserve for the germinating embryo during its early growth. The endosperm is made up mostly of starch. It also contains sugars, proteins, and fats. The hull is the hard cover of the seed. Most improved rice cultivars either do not have awns, or the awn is very small.

Awn

Hull

Endosperm Kernel Embryo

The seed was cut lengthwise

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Manual for hybrid rice seed production

Reproductive parts of the rice plant

I

The spikelet Process of seed formation Stages of seed formation Inbred rice seed Hybrid rice seed

The spikelet The stamens are the male reproductive organs. Each stamen is made up of an anther, which contains pollen grains, and the filament. The pistil is the female reproductive organ. It is made up of the ovary, a short style, and two feathery stigmas.

Pedicel

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Process of seed formation Pollination is the first step in reproduction. Pollen grains are shed from the anthers and fall onto the feathery stigmas. Fertilization is the second step in seed formation. The pollen that reaches the stigma germinates and forms a pollen tube that carries the male nuclei inside the ovary for fusion with the egg nuclei. The complete process from pollination to fertilization takes from 18 to 24 hours.

Male nucleus 2 Male nucleus 1

Fertilization

Stages of seed formation The fertilized egg cell begins development within 12 hours after fertilization. The endosperm of the developing seed begins turning milky white 8 days after fertilization. The embryo develops after 10 days. The endosperm turns into the soft dough stage at 14 days after fertilization, and the hard dough stage 7 days later. Within 25-30 days after fertilization, the ovule has matured and fully ripened into a seed.

Anther opening and fertilization

2

3

4

8

9

10

12

Milk stage

4

Manual for hybrid rice seed production

5

6

14 21 Soft dough Hard dough stage stage

7 days

30 days Fully ripe

Inbred rice seed Ordinary or inbred rice seed is produced when the egg inside the ovary is fertilized by pollen grains shed from: -anthers borne in the same spikelet. - anthers from other spikelets of the same plant. -anthers from the spikelet of another plant of the same variety. When farmers plant an entire field to a single variety, they are producing inbred seed.

Pollen from the same spikelet

Hybrid rice seed Hybrid rice seed is produced when the egg is fertilized by pollen from the anthers of a rice plant from a different variety or line. Hybrid rice seed is the first filial (F1) generation of a cross of two rice varieties that are genetically different.

Variety X

Hybrid rice seed

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Hybrid rice parental lines

I

Male sterile line Maintainer line Restorer line

Male sterile line A rice line that cannot produce viable pollen due to the interaction between cytoplasmic and nuclear genes is described as being cytoplasmic male sterile (CMS). It is used as a female parent for hybrid rice seed production. The male sterile line is commonly called a CMS line, the seed parent, the female parent, or the A line. Panicles may not exsert fully. Their basal portion remains inside the flag leaf sheath. Anthers are pale or white and shrivelled. The flowering period usually lasts for 7 days.

Shrivelled anther

Panicles not fully exserted from the flag leaf

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Manual for hybrid rice seed production

Maintainer line A maintainer line is similar to a CMS line except that it has viable pollen grains and normal seed setting. The maintainer line is used as a pollinator for maintaining a CMS line. The maintainer is also called the B line. The B line cannot restore fertility to the F1 generation when it is crossed with a CMS line. Panicles exsert fully out of the flag leaves. Anthers are yellow, plump, and shed pollen. The B line flowers 2-3 days earlier than the CMS line. Flowering lasts for about 5 days.

Spikelet of maintainer/restorer line

Restorer line Any rice cultivar that restores fertility in the F1 when it is crossed to a CMS line is called a restorer. The restorer is also called the pollen parent, the male parent, or the R line. The R line is used as the pollinator for the CMS parent for hybrid seed production. Growth duration may or may not be similar to that of CMS lines. Panicles exsert fully out of the flag leaves. Anthers are yellow, plump, and shed pollen. Flowering lasts for about 5 days.

Seed parent A line

F1 produces unviable pollen grains and resembles CMS line

Maintainer B line

Pollen parent or restorer R line

F1 produces viable pollen and sets seeds, which are used to plant commercial rice crop

Manual for hybrid rice seed production

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Desirable characteristics of parental lines Desirable characteristics of the CMS line Desirable characteristics of maintainer and restorer lines Choice of parents for hybrid seed production

Desirable characteristics of the CMS line High seed yields depend on desirable panicle, floret, and stigma characteristics of the CMS line. The panicle should be exserted from the flag leaf as far as possible. There should be at least 100 spikelets per panicle. The floret should open wide and remain open for at least 45 minutes or longer. Blooming florets should have exserted stigmas. Stigmas should be receptive to pollination for 5 to 7 days. stigma Shrivelled

exserted from the

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Manual for hybrid rice seed production

Desirable characteristics of maintainer and restorer lines Desirable characteristics of maintainer and restorer lines are the same. Panicles should be: —long and contain 125 or more spikelets. —completely exserted from the flag leaf. Filaments should be long for complete anther exsertion from the floret. Anthers should be large and plump with many pollen grains. The anther should shed most of its pollen only after it has exserted from the floret.

Panicle completely exserted from

Choice of parents for hybrid seed production Seed growers normally produce seeds of F1 hybrids released for commercial cultivation in their country. The parental lines should be adapted to the grower's area, even if the hybrid seed may be produced for another geographical area.

Government agencies or commercial seed companies are the grower's best source of parental seed of hybrids that are popular with farmers.

Manual for hybrid rice seed production

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Seeding of parental lines in the seedbed

I

Why seed in the seedbed Seedbed preparation Pregerminating seeds Managing the seedbed

Why seed in the seedbed Seeding in the seedbed ensures proper germination of the parental seed material. The seedbed provides healthy and vigorous seedlings for transplanting.

10

Manual for hybrid rice seed production

Seedbed preparation Puddle the seedbed field twice at an interval of 7 days to destroy any germinated rice seeds or weed seeds. Construct 5-10 cm raised seedbeds of approximately 1 m width of any convenient length. Construct drainage channels between seedbeds to drain excess water. Apply 5-6 grams of NPK (14:14;14) fertilizer or ammonium phosphate (16:20) fertilizer for each square meter of seedbed area and mix it with the soil. Nitrogen increases seedling growth and induces tillering. 1m

Construct raised seedbeds

Pregerminating seeds Soak the seeds in water for 24 hours. Stir the seeds upon soaking and discard those that float on the surface. Incubate the seeds for 24 hours in a warm and shady place. Seeds can be incubated in moist jute sacks. Allow room in the sacks for expansion of the seeds during incubation. Incubation keeps the seeds warm, increases growth of the embryo, and results in uniform germination. Sow pregerminated seeds uniformly on the seedbed at the rate of 1 kg seed per 20 m2 of seedbed. To produce enough seedlings to grow 1 hectare of hybrid rice, you need 15 kg of A line seed and 5 kg of R line seed.

Water level

.--

Incubate 24 hours

Seed at the rate of 1 kg of seed per 20 m2 of seedbed

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Managing the seedbed Irrigate the seedbed to a depth of 2-3 cm. Drain off the water occasionally to attain vigorous seedlings. Gradually increase water depth to 5 cm to control weeds. Pull remaining weeds by hand; weeds compete with seedlings for light, water, and nutrients.

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Manual for hybrid rice seed production

Synchronization of flowering Differential seeding How to determine seeding time of A and R lines

I

Differential seeding Success in CMS line multiplication or growing hybrid seed depends on synchronizing the flowering of the seed parent and the pollen parent. By synchronizing flowering, we mean that the seed and the pollinator parents flower at the same time in the field, even though they may have different growth durations. Synchronizing flowering is important because we want pollen from the B or R line to be available to the A line throughout its flowering period. Synchronization,of flowering can be done in two ways:

(1) We can adjust the seeding dates of the parents in the seedbed so they flower at the same time in the field. That is called differential seeding. Seeding time always depends on the growth duration of the parents, whether you are multiplying a CMS line or producing hybrid seed. (2) We can adjust the flowering date in the field by crop management practices later in the growing season. These are explained in the chapter entitled Adjusting flowering date, beginning on page 34.

How to determine seeding time of A and R lines In hybrid seed production, we normally seed the R line three times. The seeding dates are separated by 3-day intervals. The A line is always seeded just once. The seeding of the A line and the second seeding of the R line are separated by the number of days difference in their growth duration. – If the A line growth duration is shorter, the second R line seeding is done before the A line.

Example 1: R line growth duration = 100 days A line growth duration = 90 days The A line has a 10-day shorter growth duration; therefore the second seeding of the R line will be 10 days before the A line. -If the A line growth duration is longer, the second R line seeding is done after the A line.

Example 2: R line growth duration = 90 days A line growth duration = 100 days The A line has a 10-day longer growth duration; therefore the second seeding of the R line will be 10 days after the A line. If both parental lines have the same growth duration, the A line seeding and the second R line seeding would be done on the same day. We do the first seeding of the R line 3 days earlier than the second seeding. We do the third seeding of the R line 3 days later than the second seeding.

Manual for hybrid rice seed production 13

Differential seeding times Differential seeding times for hybrid seed production - Seed parent has 10-day shorter growth duration than pollen parent - Seed parent has 10-day longer growth duration than pollen parent

- Seed parent has same growth

duration as pollen parent Differential seeding times for CMS multiplication

Differential seeding times for hybrid seed production Seed parent has 10-day shorter growth duration than pollen parent

Number of seedings: A line-one R line-three Begin the seeding sequence by seeding the R line on the first day. 4 Do the second seeding of the R line 3 days after the first seeding. Do the third seeding of the R line 3 days after the second seeding. Seed the A line 7 days after the third seeding of the R line. The three seedings of the R line will supply pollen for a prolonged duration during the flowering period of the A line.

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Manual for hybrid rice seed production

Seed parent has 10-day longer growth duration than pollen parent

Number of seedings: A line-one R line-three Begin the seeding sequence by seeding the A line on the first day. Do the first seeding of the R line 7 days after the seeding of the A line. Do the second seeding of the R line 3 days after the first seeding. Do the third seeding of the R line 3 days after the second seeding. The three seedings of the R line will supply pollen for a prolonged duration during the flowering period of the A line.

Seed parent has same growth duration as pollen parent

Number of seedings: A line—one R line—three Begin the seeding sequence by seeding the R line on the first day. Do the second seeding of the R line 3 days after the first seeding of the R line. Seed the A line on the same day as the second seeding of the R line. Do the third seeding of the R line 3 days after the second seeding. The three seedings of the R line will supply pollen for a prolonged duration during the flowering period of the A line.

-1

Manual for hybrid rice seed production

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Differential seeding times for CMS multiplication Number of seedings: A line-one B line-two Do differential seeding of A and B lines to synchronize flowering. Begin the seeding sequence by seeding the A line on the first day. Do the first seeding of the B line 3 days after seeding of the A line. Do the second seeding of the B line 3 days after the first seeding of the B line. The two seedings of the B line will supply pollen for a prolonged duration during the flowering period of the A line.

/

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Manual for hybrid rice seed production

Selection of CMS multiplication and hybrid seed production fields

I

Requirements Distance isolation Time isolation Barrier isolation

Requirements To grow any rice crop, the requirements for sunlight, soil fertility, and water remain the same. All rice crops require: — fertile soil. — adequate irrigation water and drainage. — sufficient sunlight for high seed yield. — management of insects and soilborne diseases.

Fields for CMS line multiplication or hybrid seed production have one more important requirement. Seed production plots must be well separated, or isolated, from other ricefields to ensure genetic purity of the seed. What we mean by protecting genetic purity is that the seed parent (or A line) is only pollinated by the male parent chosen as the B line or the R line.

Pollen from different rice cultivars near seed production plots can contaminate the seed parent and lower the quality of the hybrid seed. Seed production crops can be isolated from other rice crops by: — distance from other ricefields. — differences in time of flowering. — natural or artificial barriers.

Distance isolation Rice pollen grains are small, light, and can be carried distances of up to 100 meters in air, within their life span of 3-5 minutes. No other rice crop should be grown within 100 m of hybrid seed production plots.

The isolation distance can be decreased to 50 m, if at least 10 border rows of the pollen parent surround the seed production plot.

50 100 m

Hybrid seed production plot

Inbred grain production plot

Manual for hybrid rice seed production

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Time isolation Adjust planting time to separate flowering time of the seed parent from other rice cultivars within 100 m by at least 3 weeks. That will protect the seed parent from contamination.

If the seed parent and a nearby cultivar have the same heading date, then the 100-m separation distance must be maintained.

At least 5 m separation

Hybrid seed production plot

Inbred grain production plot Difference in flowering is more than 3 weeks

Barrier isolation Any natural, artificial, or crop barrier over 2.5 m high can prevent contamination of the seed parent by pollen grains from rice cultivars within 100 m.

Hybrid seed production plot

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Manual for hybrid rice seed production

The crop barrier around the seed production plots should be 3-4 m wide, depending upon the type of crop.

3-4 m Sesbania

Sesbania rostrata or a healthy, tall crop of maize, sorghum, or pearl millet makes a satisfactory barrier.

Inbred grain production plot

Transplanting

I

Why transplant How to transplant How many seedlings per hill Layout for transplanting Seedling age at transplanting

Why transplant Transplanting gives proper plant spacing, resulting in uniform growth. Transplanting gives the optimum crop stand for getting maximum seed yield. Transplanting makes field operations such as weeding, spraying, fertilizing, and roguing easier. Hybrid rice is planted in rows in only one direction; plants within rows do not line up across rows.

How to transplant Seedlings should be transplanted straight upright for early establishment. Seedlings should be transplanted 2-3 cm deep in the soil for early plant recovery and better tillering.

2-3 cm deep

Manual for hybrid rice seed production

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How many seedlings per hill There is no difference in seed yield between one and two seedlings per hill, unless the seedling planted alone dies. Transplant one or two seedlings per hill of the A line.

Layout for transplanting The rows in the seed production plot should be perpendicular to the prevailing wind direction expected at flowering time of the parents. Plants in alternate rows should be offset from one another to give A line plants a greater chance to intercept pollen from the B or R lines at flowering. When the plants are properly offset, they appear to have been transplanted in a crisscross fashion. Plant spacing within rows does not change.

Transplant two seedlings per hill of B or R lines. The seed is plentiful and if one seedling dies, the remaining seedling can produce sufficient tillers.

.. . ...

Conventional transplanting

Hybrid rice transplanting

Wind direction

A line

Seedling age at transplanting Transplanting 21-day-old seedlings ensures timely heading and flowering of parental lines. Transplanting older seedlings delays flowering by about half the number of days by which the seedlings are older than 21 days.

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Manual for hybrid rice seed production

Transplanting younger seedlings advances flowering by approximately half the number of days by which the seedlings are younger than 21 days. If transplanting of seedlings of the A line is delayed, then delay transplanting the B or R line seedlings by the same number of days to synchronize flowering.

Transplanting in a specific row ratio What is a row ratio Factors influencing row ratio - Characteristics of the R line - Characteristics of the A line - Flowering behavior of the A and R lines

What is a row ratio Row proportion or row ratio refers to the number of rows of the male parent (B or R line) to that of the female parent (A line) in a seed production plot. For example, if we plant 2 rows of the B or R line for every 8 rows of A line, we say we have a row ratio of 2:8. The row ratio of pollen parent to seed parent will vary from region to region, depending on weather, management, and parental lines. R and A lines can be planted in several row ratios: 2:8, 2:12, 3:10, etc. In this manual, we take an R:A line ratio of 2:8 as normal and use it in most examples.

Manual for hybrid rice seed production

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Factors influencing row ratio The ratio of pollen parent (R line) to seed parent (A line) is determined by the characteristics of the parental lines. Characteristics of the R line

There can be more than 8 A line rows in relation to the 2 rows of the pollen parent if R line plants: -are taller than the seed parent. -have good growth and vigor. -have large panicles. - shed a large amount of residual pollen (the pollen left in the anther at the time of spikelet opening).

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Manual for hybrid rice seed production

Characteristics of the A line

There can be more than 8 A line rows in relation to the 2 rows of pollen parent if the A line: - is shorter than the pollen parent. -has a long duration of floret opening and stigma receptivity. -has a wide angle of floret opening. -has a high percentage of stigma exsertion.

Flowering behavior of the A and R lines

The A and R lines should flower at the same time. The A and R lines should be in full bloom at the same time of day during the flowering period. Pollination increases if both the A and R lines have the maximum number of blooming spikelets per unit area per day. That assures that the maximum amount of pollen is available when the maximum number of stigma are receptive to pollination.

Transplanting sequence for CMS multiplication

I

Transplanting the A line Transplanting the B line

Transplanting the A line Number of transplantings: A line-one B line-two Seedling age: 21 days Row ratio: 2:6 On the first day of the transplanting sequence, transplant the A line seedlings in blocks of 6 rows. Space rows 15 cm apart with 15 cm between seedlings within rows.

Leave a 75-cm wide block between blocks of A line seedlings for transplanting seedlings of the B line.

Transplanting the B line Transplant seedlings from first B line seeding in paired rows on the 4th day of the transplanting sequence. -Space rows 15 cm apart with 30 cm between seedlings within rows.

-Leave a 30-cm wide alleyway between the B line rows and the nearest A line rows. Transplant seedlings of the second B line seeding according to the transplanting sequence chart. -Fill in the vacant spaces in the rows so that plant spacing is 15 cm within rows after the second B line seedlings have been transplanted.

Manual for hybrid rice seed production

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Transplanting sequence for hybrid seed production Seed parent has 10-day shorter growth duration than pollen parent Seed parent has 10-day longer growth duration than pollen parent Seed parent has same growth duration as pollen parent

Seed parent has 10-day shorter growth duration than pollen parent Number of transplantings: A line-one R line-three Seedling age: 21 days Row ratio: 2:8

24

Transplanting the R line

Transplant seedlings from first R line seeding in paired rows. -Space rows 15 cm apart with 45 cm between seedlings within rows. Leave a 165-cm wide block between paired rows of R line seed-

lings for transplanting 8-row blocks of A line seedlings. Transplant seedlings of the second and third R line seedings according to the transplanting sequence chart. -Fill in the vacant spaces in the paired rows so that plant spacing is 15 cm within rows

Manual for hybrid rice seed production

[email protected]@.O

after the seedlings of the third R line seeding have been transplanted.

Transplanting the A line

Transplant the A line seedlings in blocks of 8 rows on the fourteenth day of the transplanting sequence.

Space rows 15 cm apart with 15 cm between seedlings within rows. Leave a 30-cm wide alleyway between the A line rows and the nearest R line rows.

Seed parent has 10-day longer growth duration than pollen parent Number of transplantings: A line-one R line-three Seedling age: 21 days Row ratio: 2:8 Transplanting the A line

On the first day of the transplanting sequence, transplant the A line seedlings in blocks of 8 rows. Space rows 15 cm apart with 15 cm between seedlings within rows.

Leave a 75-cm wide block between blocks of A line seedlings for transplanting the seedlings of the R line. Transplanting the R line

Transplant seedlings from first R line seeding in paired rows on the eighth day of the transplanting sequence. -Space rows 15 cm apart with 45 cm between seedlings within rows.

-Leave a 30-cm wide alleyway between the R line rows and the nearest A line rows. Transplant seedlings of the second and third R line seedings according to the transplanting sequence chart. -Fill in the vacant spaces in the paired rows so that plant spacing is 15 cm within rows after seedlings of the third R line seeding have been transplanted.

Manual for hybrid rice seed production

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Seed parent has same growth duration as pollen parent Number of transplantings: A line—one R line—three Seedling age: 21 days Row ratio: 2:8 Transplanting the R line

Transplant seedlings from first R line seeding in paired rows. -Space rows 15 cm apart with 45 cm between seedlings within rows. Leave a 165-cm wide block between paired rows of R line seedlings for transplanting 8-row blocks of A line.

26

Transplant seedlings of the second and third R line seedings according to the transplanting sequence chart. - Fill in the vacant spaces in the paired rows so that plant spacing is 15 cm within rows after seedlings of the third R line seeding have been transplanted.

-Leave a 30-cm wide alleyway between the A line rows and the nearest R line rows.

Transplanting the A line

Transplant the A line seedlings in blocks of 8 rows on the fourth day of the transplanting sequence. Space rows 15 cm apart with 15 cm between seedlings within rows.

Manual for hybrid rice seed production

NOTE: The seedlings of the second seeding of the R line and the A line seeding are planted on the same day in the sequence. Be especially careful not to mix seedlings of the two lines during transplanting.

Seeding and transplanting modifications to increase seed yield Change the seedling proportion of R line Seed the R line twice Modify row ratios Modify row and plant spacings Transplant R line seedlings on the same day

Change the seedling proportion of R line Experienced growers can change seeding and transplanting patterns to increase hybrid seed yield. Apprentice growers plant an equal number of seedlings in each of the three transplantings of the R line. Experienced growers can double the number of seedlings from the second seeding. The transplanting

pattern within R line rows should be as shown in the illustration. Doubling the number of seedlings from the second seeding increases the amount of residual pollen that will be available to the seed parent at peak flowering. The seedbed for the second seeding of the R line should be twice as

large as the seedbeds for the first and third seedings. Transplant seedlings when they are 21 days old. The figure shows the transplanting pattern when the seed parent has 10 days longer growth duration than the pollen parent.

Manual for hybrid rice seed production

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Seed the R line twice Seed the R line twice instead of three times. Adjust the size of your seedbeds so that the number of seedlings from the first seeding is twice that of the second seeding. The first seeding of the R line should be timed to synchronize flowering with the A line. The second seeding of the R line is done 3 days after the first seeding of the R line. Transplant seedlings when they are 21 days old. The drawing shows the transplanting pattern used when the seed parent has a 10-day shorter growth duration than the pollen parent.

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Manual for hybrid rice seed production

Modify row ratios Experienced growers can change the row ratio of R lines to A lines. Instead of a row ratio of 2:8, a ratio of 2:10, 2:11, or 2:12 can be use

When the grower has perfected the technique of synchronizing the flowering of R and A lines, a row ratio of 1:8, 1:9, or 1:10 may be used.

I

1

1

1

1

1

1

1

1

1

I

Modify row and plant spacings Row and plant spacings can be modified from the recommended 15- x 15-cm spacing, depending on local conditions. When row and plant spacings are increased, the ratio of A line panicles to R line panicles should remain the same. -The number of productive tillers per hectare should not be less than 3 million for the A line or 1 million for the R line. A productive tiller is a tiller that produces a panicle. -There should be a ratio of 3-3.5 A line panicles to 1 R line panicle.

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Transplant R line seedlings on the same day Sequential transplanting of seedlings of the three R line seedings ensures that the most residual pollen is available to the A line at flowering. However, the practice is labor-intensive. The seedlings of the three R line seedings can be transplanted on the same day. This modified practice requires changing the seeding dates of the R line. The seeding interval between the first, second, and third R line seedings is increased from 3 days to 5 days. The second R line seeding is done so that flowering of this seeding synchronizes with flowering of the A line. Do the three seedings of the R line and the seeding of the A line according to the seeding sequence. R line seedlings are transplanted when the seedlings from the second R line seeding are 21 days old. That means that the seedlings from the first seeding will be 26 days old. The seedlings from the third seeding will be 16 days old. Transplant R line seedlings according to the pattern shown in the drawing. The A line seedlings are transplanted to synchronize flowering with the second R line seeding. - Transplant 21-day-old seedlings of the A line 10 days earlier than the R line seedlings if the A linehas a 10-day longer growth duration. - Transplant 21-day-old seedlings of the A line 10 days later than the R line seedlings if the A line has a 10-day shorter growth duration. - Transplant 21-day-old seedlings of the A line on the same day as the R line seedlings if the A line has the same growth duration.

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Manual for hybrid rice seed production

Management of seed production plots

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Retransplant missing hills Control weeds Control diseases and insect pests Fertilizer management

Retransplant missing hills Keep the field saturated until the plants recover in 4 or 5 days. Then increase the water level to 5 cm. Replant all the missing hills within 7 days of transplanting. Be careful not to mix A and R seedlings when you replant missing hills.

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Control weeds Keep the weeds under complete control. Weeds can be controlled by: —hand pulling. — mechanical means such as weeders. —herbicides.

Control diseases and insect pests Keep diseases and insect pests under complete control. Follow insect and disease control practices recommended for your area. Because hybrid seed production is expensive, it is necessary to completely control insect pests and diseases to obtain maximum seed yield.

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Manual for hybrid rice seed production

Fertilizer management Apply fertilizers at rates recommended for lowland irrigated conventional rice cultivars in your area. You should not use a blended fertilizer, such as NPK, on hybrid seed production plots because nitrogen (N) fertilizer will be applied separately from phosphorus (P) and potassium (K). Apply the entire amounts of recommended P and K to the seed production plots just before the last puddling. Nitrogen should be applied to each parent in three splits. The normal application schedule is: one-third 5-7 days after transplanting, one-

third 20-25 days after the first application, and the final one-third at maximum tillering. In hybrid rice seed production plots, seedlings are not all transplanted at the same time. For that reason, N application timing must be adjusted. First split: —Do not apply N to the R line rows until 5-7 days after the last R line is transplanted. —Divide the first split between the R line rows and the A line rows in proportion to the field space allotted to each parent.

Second split: —Apply the second split to the entire seed production plot. —The second split should be applied 20-25 days after the last fertilizer application to the plot.

Third split: —Apply the remaining one-third to the entire seed production plot at maximum tillering.

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Adjusting flowering date Synchronization of flowering date of parental lines Panicle initiation and flowering date How to observe panicle initiation Developmental stages of panicle formation to flowering Estimating flowering date by panicle primordium stages

How to adjust flowering dates of parental lines showing 5-6 days difference at panicle initiation How to adjust flowering dates of parental lines showing a difference of more than a week

Synchronization of flowering date of parental lines We try to synchronize flowering of parental lines by differential seeding. Weather fluctuations during the growing season and crop management practices may cause the parental lines to flower on different dates.

When flowering is not synchronized, hybrid seed yield will be reduced. Flowering date of parental lines cannot be accurately predicted until the crop is at maximum tillering stage.

Panicle initiation and flowering date Flowering date is predicted on the basis of panicle initiation. Panicle initiation begins at maximum tillering in all rice cultivars. Flowering occurs in all cultivars about 30 days after panicle initiation. The young panicle (panicle primordium) becomes visible (with a magnifying lens) within - 40-45 days of seeding in cultivars maturing in 95-100 days. - 50-52 days of seeding in cultivars maturing in 105-110 days. - 60-62 days of seeding in cultivars maturing in 115-120 days. - 65-70 days of seeding in cultivars maturing in 125-130 days.

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Manual for hybrid rice seed production

How to observe panicle initiation Select the longest growing tiller (main tiller) and cut it at the base where stem and root . Slit the stem lengthwise from the base up to the top of the tiller. Open the slit immediately above the nodal portion. Observe the developing panicle (preferably with a magnifying lens). It is about 1 mm long.

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Developmental stages of panicle formation to flowering The young panicle undergoes 10 developmental stages before it finally emerges out of the flag leaf sheath.

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Manual for hybrid rice seed production

Estimating flowering date by panicle primordium stages For complete flowering synchronization, the pollen parent should be one stage earlier than the seed parent during stages I, II, and III of panicle development. Both parents should be in the same stage during the 4 middle stages IV, V, VI, and VII. The seed parent should be slightly earlier than the pollen parent during stages VIII, IX, and X of panicle development.

How to adjust flowering dates of parental lines showing 5-6 days difference at panicle initiation Presuming Pollen parent Stage I indicating late flowering

Seed parent Stage III indicating early flowering

Delay the flowering date of the seed parent -by spraying quick releasing nitrogen fertilizer (urea 2% concentration) immediately after observing that the panicle in the seed parent is at stage III. Advance the flowering date of the pollen parent -by spraying 1% solution of phosphate fertilizer immediately after observing the panicle development stage in the pollen parent, or -by keeping water standing in the field.

How to adjust flowering dates of parental lines showing a difference of more than a week Presuming Pollen parent Stage I indicating late flowering

Seed parent Stage IV indicating early flowering

Remove the panicles from the main tiller of the seed parent. Spray 2% urea and also add nitrogenous fertilizer to the seed parent to make unproductive, late tillers bear productive panicles and achieve synchronization of flowering. Advance the flowering date of the pollen parent -by spraying 1% solution of phosphate fertilizer immediately after observing the panicle development stage in the pollen parent, or -by keeping water standing in the field.

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Flag leaf clipping

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Crop stage for flag leaf clipping Flag leaf clipping method

Crop stage for flag leaf clipping Flag leaves should be clipped when primary tillers are at booting stage. Flag leaf clipping enhances uniform pollen movement and wide dispersal of the pollen grains to give higher seed set.

Flag leaf clipped when primary tillers are at booting stage

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Manual for hybrid rice seed production

Flag leaf clipping method First, hold the upper leaves of the plant and with one horizontal stroke of the scythe cut the flag leaves at a level just above the flag leaf t of the main tiller. Experienced growers may cut onehalf to two-thirds of the blade of the flag leaf back from the top. Do not clip the flag leaves in plots infected with bacterial leaf blight,

bacterial leaf streak, or sheath blight. The cut leaves can infect other plants, or infection can be spread by contaminated tools used for flag leaf clipping. Alternatively, flag leaf clipping of the infected area can be done after flag leaves have been clipped from healthy plants in the plot.

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Gibberellic acid application Why spray gibberellic acid Timing of application-crop growth stage Timing of application-weather conditions How to make GA3 solution-general procedure

How to make GA3 solution-amount required for different plot sizes How to make GA3 solution-doing your own computations

Why spray gibberellic acid Gibberellic acid can also be written as GA3. We spray hybrid rice seed production plots with GA3 to: - adjust plant height of both parents. -increase the growth rate of secondary and tertiary tillers so that they bear panicles.

In the seed parent, GA3: panicle exsertion from the flag leaf. -increases the duration of floret opening. -increases the rate of stigma exsertion and lengthens the duration of stigma receptivity. - enhances

Timing of application-crop growth stage Hybrid rice seed production plots are usually sprayed twice. The first spraying of GA3 is done when 15-20% of the tillers have started heading. The second spraying should be done 2 days after the first spraying, or when 35-40% of the panicles of the seed parent have emerged.

First spraying (15-20% heading)

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Manual for hybrid rice seed production

Second spraying (35-40% heading)

Timing of applicationweather conditions Spray in the afternoon on a sunny day. Do not spray if rain is expected within 24 hours. Spray on calm days to prevent spray from drifting onto nearby fields. Spraying on windy days wastes spray because it is carried away from the seed production plots.

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How to make GA3 solution-general procedure GA3 is sold as a powder. It comes in purity levels of 100% pure and 90% pure. The purity of the GA3 powder controls the amount you use to make the spray solution. The concentration of GA3 mixed with water to make the spray solution is measured in parts per million (ppm). For example, 3 grams of GA3 dissolved in 50 liters of water will give 60 ppm concentration. Use 500 liters of water per hectare when spraying with a knapsack sprayer. Use 20 liters of water per hectare when spraying with an ultra-low volume sprayer. Use a correspondingly smaller amount of water for areas less than a hectare.

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Manual for ybrid rice seed production

The concentrations depend on the type of sprayer you use and whether you are doing the first spraying or the second spraying. GA3 spray concentration (ppm) Spraying

Knapsack

Ultra-low volume

First Second

60 30

500 250

GA3 powder will not dissolve in water. It must be dissolved in a small amount of 70% ethanol (grain alcohol) before it is mixed with water. A liquid dish detergent or laundry detergent should be added to the solution. The detergent makes GA3 stick to the leaf surface for more efficient coverage of the plants.

How to make GA3 solution—amount required for different plot sizes How to use these charts: These two charts will help you select the right amount of GA3 to add to a given volume of water for the required concentration. There is one chart to follow when using a knapsack sprayer, and another when using an ultra-low volume sprayer. Each chart gives information for making the proper concentration for the first and second spraying. Be sure to use the correct amount of GA3 depending on the purity of the chemical. Always dissolve the GA3 powder in a small amount of 70% ethanol (grain alcohol) first, and then mix with the required amount of water. To make sure you understand how to use the charts, find the amount of GA3 needed to make up enough solution to spray a 2,000 m2 plot using knapsack sprayer. Assume you have GA3 of 90% purity and you want a 60 ppm concentration. According to the chart, you would need 6.7 grams of GA3 (dissolved in 70% ethanol) to make 100 liters of spray.

Knapsack sprayer Amount of GA3 in grams required for a given volume of water and given concentration of solution. Use the appropriate number (GA3) under the 100% or 90% columns, depending on the purity of chemical.

Area (m2)

Waier volume (liter)

Concentration 60 ppm 100%

30 ppm 90%

100%

90%

Ultra-low volume sprayer Amount of GA3 in grams required for a given volume of water and glven concentration of solution. Use the appropriate number (GA3) under the 100% or 90% columns, depending on the purity of chemical.

Area (m ) 2

Water volume (liter)

Concentration 500 ppm 100%

250 ppm 90%

100%

90%

Manual for hybrid rice seed production

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How to make GA3 solution—doing your own computations

Plot size (m2) x 500 10,000

= volume of water.

By substituting our plot size, 2,000 m2, we obtain 2,000 x 500 1,000,000 = 100 liters = 10,000 10,000

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Manual for hybrid rice seed production

Desired concentration Ultra-low volume sprayer

500 ppm GA3, purity

You can compute the amount of GA 3 and water required for any size plot. For the example, we assume: -a GA3 source of 90% purity. -a knapsack sprayer. - a 2,000-m2 seed production plot. -a 60 ppm concentration is desired. First, calculate the amount of water required to spray the plot. The volume of water required to spray 1 ha is 500 liters. We calculate the volume required to spray 2,000 m2 as shown:

90% 100%

250 ppm

Knapsacksprayer

60 ppm

30 ppm

1.1

0.56

0.067

0.033

1

0.5

0.06

0.03

We then multiply the amount of water by the amount of GA3 of either 90% or 100% purity required for the desired concentration. Take that number from the table provided. Since we are using a knapsack sprayer and assume a GA3 purity of 90%, we take the number 0.067. Multiply it by 100, the amount of water we calculated was required to spray a 2,000 m2 plot: 100 ´ 0.067 = 6.7 grams GA3 required to make 100 liters of 60 ppm concentration.

to add about 5-10 ml of liquid detergent to every 50 liters of spray solution.

Supplementary pollination

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Methods of supplementary pollination Timing of supplementary pollination

Methods of supplementary pollination Supplementary pollination is artificially shaking the canopy of the pollen parent at flowering to increase cross pollination. Supplementary pollination -causes anthers to shed all of their pollen. - disperses pollen grains uniformly over the seed parent plants. -increases seed set in the seed parent. Supplementary pollination is done by -two persons pulling a 1-cm diameter rope along the two R lines. -one person stirring the canopy layer of the R lines with a bamboo stick, taking care not to break off the panicles at the neck.

Timing of supplementary pollination Supplementary pollination is done on calm days when wind speed is so low (1-3 km/hour) that it causes little or no movement of the crop canopy. Wind speed that low is not enough to disperse pollen uniformly to the seed parent. If there is enough wind (8-10 km/ hour) to cause moderate movement in the crop canopy, supplementary pollination is not needed.

Begin supplementary pollination in the morning, but not before the seed parent has started blooming. If the seed parent is blooming, begin as soon as the first florets of the pollen parent begin to open. Stir the canopy every 30 minutes until all blooming florets in the pollen parent are closed.

.

Continue supplementary pollination even after the florets of the seed parent have closed, because exserted stigmas are still receptive to pollen.

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Roguing What is roguing and why is it necessary Crop stage for roguing Off-types to be remove — At maximum tillering — At flowering — Before harvest

What is roguing and why is it necessary Roguing is the removal of undesirable rice plants from hybrid seed production plots. Undesirable rice plants are plants in either the A line or R line rows that differ from plants that are true to type. They may be volunteer plants from an earlier crop or offtypes.

Roguing prevents off-types from cross pollinating with true-to-type A line plants and lowering the purity of the hybrid seed. Roguing ensures that the hybrid seed produced will be a cross between only the A line and R line parents. That in turn ensures that the commercial plantings of the hybrid seed produced will give high yields.

High purity hybrid seed will increase your reputation as a seed grower.

Crop stage for roguing Roguing can be done at any time of the crop stage. Off-type rogues can be removed from the crop whenever they appear. The most important stages for roguing are: — at maximum tillering. — at flowering. — just before harvest.

Maximum tillering

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Manual for hybrid rice seed production

Flowering

Before harvest

Off-types to be removed Remove plants that are off-type in leaf blade size or shape. Remove plants that are off-type in color of the leaf sheath or leaf collar.

At maximum tillering Remove any plants outside the rows. Remove plants that are considerably taller or shorter than the seed or the pollen parents.

....

.

......... ........... ...........

utside the rows

Off-type in leaf blades

Off-type in color

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A t flowering

Remove off-type plants that flower very early or very late. Remove plants that are off-type in leaf size, leaf angle, and panicle shape and size. Remove plants from the A line that have plump, yellow anthers and shed pollen. Plants in the A line should not have viable pollen. Remove plants with fully exserted panicles from the A line. Remove all diseased plants from the seed production plot.

Before harvest

In A line rows, remove plants that have normal seed set. Remove off-types that have different grain characters from the normal A line plants. Look for differences in grain shape, grain size, or the presence or absence of awns. Remove plants from A line that have normal seed set

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Manual for hybrid rice seed production

Harvesting

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Special considerations for harvesting hybrid rice When to harvest Harvesting the B or R line Harvesting the A line

Special considerations for harvesting hybrid rice Harvesting hybrid rice seed production plots is different from harvesting a rice grain crop. Harvest the R line first, and then harvest the A line. The A line harvest is the only one that can be sold as hybrid seed. The

R line harvest may be sold as grain or kept for home use. The A line harvest and the R line harvest must be kept separate from each other during harvesting, threshing, drying, and bagging.

When to harvest Harvest when 90% of the grains in the main panicles of the A line plants are clear, firm, and straw colored. The rest of the grains should be in the hard dough stage. Harvest when seed moisture is less than 20%.

Drain the hybrid seed production field 7-10 days before expected harvest. Draining the field makes the crop mature faster and helps to achieve uniform maturity in the crop.

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Harvesting the B or R line Harvest all B or R line rows first. Harvest the plants manually by cutting them off at the base with a sickle or scythe. Remove the R line harvest and store it in a safe place for threshing later.

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Manual for hybrid rice seed production

Do not leave even one panicle in the field. It could be mixed with the A line harvest and reduce the purity of the hybrid seed.

Harvesting the A line Rogue the A line rows one more time before harvest. - Remove plants with normal seed set. -Remove any other plants that appear to be off-types.

The A line can be harvested manually or with a mechanical combine. If a combine is used, it should have adjustable field speed and clearance to prevent field loss or grain damage.

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Threshing

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Preparation for threshing Threshing the seed parent Threshing the pollen parent

Preparation for threshing During threshing, the seed parent and pollen parent harvests must be kept separate from each other. The seed parent should not get mixed with other seed or grain on the threshing floor or with any left over in the thresher. All threshing equipment and the threshing floor should be thoroughly cleaned before starting threshing. New jute sacks should be available for bagging the seed. If new sacks are not available, then use clean used sacks. The used sacks must not contain any rice grains that could be mixed with the hybrid seed. Make two labels for each bag — one to place inside the bag and one to attach to the outside. Each label should contain the following information: (1) your name and address. (2) the name of the hybrid. (3) the location of the seed production field. (4) season.

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Manual for hybrid rice seed production

Separate A line from R line during threshing

Threshing the seed parent Thresh the seed parent first to keep it from being mixed with any other seed. Thresh the seed manually with a hand flail on a threshing floor or with a manual or engine-driven thresher. Dry the threshed seed of seed parent immediately.

....-

Threshing the pollen parent The pollen parent should be threshed separately and used as grain. It should not be used as seed.

Thresh the seed parent first

Sun dry

Clean the threshing equipment

Thresh seed manually

Thresh the pollen parent

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Seed drying

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Why seed drying Seed drying methods-sun-drying Seed drying methods-forced air drying

Why seed drying Seeds can be safely stored when they have been dried to a moisture content of 13% Drying helps seeds maintain their ability to germinate and their vigor for a longer period.

Drying controls mold growth and the activity of other organisms that reduce the quality of stored grain. Drying reduces seed discoloration, which lowers the market value of the seed.

Seed drying methods- sun-drying Seeds can be sun-dried on a threshing floor. Do not dry the seeds directly on the concrete threshing floor. Place them on jute bags or on a tarpaulin. Stir the seeds occasionally to ensure uniform drying.

Seed drying methods— forced air drying Seeds can be dried in a batch-type dryer by forced air heated to 4045 °C. Do not dry the seeds abruptly to 13% moisture content if the beginning seed moisture is higher than 20%. The seed layer in a batch-type dryer should not be more than 45 cm deep.

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Manual for hybrid rice seed production

Processing hybrid rice seed for market

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Cleaning and grading Seed germination testing Packing and labeling the seed

Cleaning and grading The purpose of cleaning the seed is to: -remove impurities such as trash, leaves, broken seeds, sand or grit, etc. -remove weed seeds or those of other plant species. - remove immature, shriveled, unfilled, and empty spikelets. Seed can be cleaned manually by winnowing. Winnowing removes only light, chaffy material. An air screen machine not only cleans the seed but separates seed of uniform size from oversize and undersize seeds. The process of separating seeds of uniform size is known as grading. Air screen machines are normally too expensive for on-farm ownership. Cleaning and grading are usually done by public or private seed agencies that contract with seed growers for hybrid seed production.

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Seed germination testing Before seeds can be packed and sold as hybrid seed, they must be tested for germination rate and purity. Public seed testing agencies normally do the testing and certification. The germination rate must be at least 85% in order for seed to be certified. Before taking your seed for testing, you can do your own germination test at home by following the instructions.

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Manual for hybrid rice seed production

(1) Spread 200 seeds evenly over new or clean jute sacks that have been soaked in water. (2) Cover the seeds with another wet jute sack. (3) Roll up the jute sacks with the seeds inside and store them in the shade for 7 days. Keep the rolled sacks moist for the entire period. Do not let them dry out. (4) Make three sets of 200 seeds. (5) At the end of 7 days, count the normal seedlings that have developed. (Normal seedlings will have well-developed roots and shoots.)

(6) All three sets of germinated seeds should have a germination rate of at least 85%. A germination rate of 85% is 170 normal seedlings for each set of 200 seeds. If the germination rate of your seeds is 85% or higher, the seeds can be packed.

Packing and labeling the seed Pack your seed in clean, preferably new, jute bags. If you store your seeds in used bags, you should disinfect the bags to protect the seed from insects that could attack the seed during storage. Follow these steps to disinfect used bags. (1) Turn the bags inside out and shake them thoroughly so no seeds of any kind stick to the inside of the bag. (2) Soak the bags for 10 minutes in a 0.15% solution of malathion. (Make the solution by mixing 1 part malathion 50 EC in 300 parts water.)

(3) Dry the bags under shade before filling them with seed. Do not pack your seed if the moisture content is more than 13%. The seed could spoil during storage. Make two labels for each bag—one to place inside the bag and one to attach to the outside. Each label should contain the following information: (1) your name and address. (2) the name of the hybrid. (3) the location of the seed production field. (4) season.

Manual for hybrid rice seed production

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