Hybrid Seed Production in Sunflower and Maize

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Slide 1: 

HYBRID SEED PRODUCTION SUNFLOWER AND MAIZE

INTRODUCTION OF MAIZE : 

INTRODUCTION OF MAIZE Family:Poaceae(Graminea) Botanical name:Zea mays Chromosome Number:2n=20 Maize plant is monoecious. The male or staminate flowers are found, on the terminal inflorescence known as tassel whereas female flowers are on the lateral branches called ear shoots(cobs)

ORIGIN OF MAIZE : 

ORIGIN OF MAIZE Maize plant is the native of America . Now it become the principle food of Indians. Maize is one of the oldest cultivated crops.

INTRODUCTION OF SUNFLOWER : 

INTRODUCTION OF SUNFLOWER Family: Compositae Genus: Helianthus Species: annuus Origin: Native of United States and Mexico Other Species: tuberosus , petiolaris Chromosome No. : Basic chromosome No, x=17 Helianthus annuus : 2n = 2x = 34 Helianthus tuberosus: 2n = 6x = 102 Helianthus petiolaris: 2n = 2x = 34

ORIGIN OF SUNFLOWER : 

ORIGIN OF SUNFLOWER Sunflower was introduced in India as an oilseed crop for the first time in 1969 . Sunflower is a new oilseed crop. But it was grown in India as an ornamental crop since ancient times.

PRODUCTION OF HYBRID SEEDOF MAIZE & SUNFLOWER : 

PRODUCTION OF HYBRID SEEDOF MAIZE & SUNFLOWER Hybrid seed may be produced by different method. Cytoplasmic-genetic male sterility Cytoplasmic male sterility Genetic male sterility Self-incompatibility Manual emasculation or pollination

CYTOPLASMIC-GENETIC MALE STERILITY : 

CYTOPLASMIC-GENETIC MALE STERILITY This system is the most widely used method in hybrid seed production. It is commercially used in Maize,Bajra,Jowar, Onion,Sunflower,Cotton&Sugarbeets. It is of two types:- Production of single cross hybrid varieties Production of double cross hybrid varieties

Production of single cross hybrid varieties : 

Production of single cross hybrid varieties For the production of a single cross ,a cytoplasmic male sterile line is used as female parent,while the male parent is a restorer. Seed set on the female parent(the male sterile line) in the hybrid seed,while that produced on the male parent is selfed seed. The resulting hybrid will be male fertile since it has received the restorer gene from the male parent. Generally two rows of male sterile inbred(the male parent) are planted after every two rows of the male sterile parent (the female parent). But when the male inbred produces sufficient pollen ,2 rows of the male inbred may be planted after every 3 or4 rows of the female parent. The present single cross hybrid varieties of maize are produced by planting male & female inbreds in the ratio of 2:4.

Production of Double cross hybrid varieties : 

Production of Double cross hybrid varieties Double cross hybrid varieties are produced by crossing two single crosses ,one male sterile and the other male fertile . The male sterile cross is produced by crossing a cytoplasmic male sterile line with a non –restorer male fertile line . Male fertile single cross is produced by two ways:- In first approach ,a cytoplasmic male sterile line is crossed with a restorer line; the double cross in this case has both male sterile &male fertile plants in the ratio 1:1. In the second method two restorer lines are crossed together ;one of the restorer lines serves as female and is detasselled manually . All the plants in the double cross ,in this case ,would be male fertile .

Slide 10: 

INBRED A Cyt. male Sterile,rr INBRED B Restorer,RR INBRED A Cyt. male Sterile,rr INBRED B Non Restorer,rr INBRED C Cyt. male Sterile,rr INBRED D Restorer,RR INBRED A Cyt. male Sterile,rr INBRED B Non Restorer,rr INBRED C Restorer,RR INBRED D Restorer,RR SINGLE CROSS D.C. SCHEME 1 D.C. SCHEME 2 Hybrid AxB Seed harvested from inbred A All plants male fertile Single cross AxB Male sterile, rr Single cross CxD Male fertile, Rr Single cross AxB Male sterile, rr Single cross CxD Male fertile, RR Double cross (AxB)x(CxD) 1 fertile,Rr;1 sterile,rr Double cross (AxB)x(CxD) All plants male fertile Rr Detassel

Progeny selection : 

Progeny selection The simplest form of progeny selection is the ear-to-row method, extensively used in Maize. This method was developed by Hopkins in 1908. In its simplest form, the ear-to-row method of selection as follows- A number(50-100)of plants are selected on the basis of their superior phenotype. They are allowed to be open-pollinate, and the seeds from individual plants are harvested separately. A single row of 10-50 plants,i.e.,a progeny row, is grown from each selected plant. The progeny rows are evaluated for desirable characters and superior progenies are identified. Several phenotypically superior plants are selected from the superior progenies. There is no control on pollination; the plants are permitted to open-pollinate. Small progeny rows, as in item 2,are grown from the selected plants, and the process of selection is repeated.

Slide 12: 

MAY BE REPEATED ONE OR MORE TIMES YIELD TRIALS Original population 1st Year 2nd Year 3rd Year (i) Plants on the basis of phenotype (ii) Open pollinated seed from each plant harvested separately Small progeny rows grown Superior progeny identified Pheno. Superior plants selected from superior progeny (iv) Plants allowed to open pollinate As same as above 1st selection cycle 2nd selection cycle 3rd selection cycle

Slide 13: 

Original population Original population MAY BE REPEATED ONE OR MORE TIMES YIELD TRIALS 1st Year 2nd Year 3rd Year 4th Year (i) Plants on the basis of phenotype (ii) Open pollinated seed from each plant harvested separately (i) and (ii) of 1st year in scheme 1 (iii) Remaining seeds from plants producing superior progenies bulked to raise the next generation Bulked seed planted Plants allowed to open pollinate Plants with superior pheno. Selected & seed harvested separately As in items (i) to (iii) in the 2nd year 1st selection cycle 2nd selection cycle

Merits of Hybrid varieties : 

Merits of Hybrid varieties Hybrid varieties exploit both GCA&SCA components of heterosis.Thus they utilize heterosis to the greatest possible extent. The produce from hybrid,particularly single cross,varieties is more uniform as compared to that from open-pollinated,synthetic or composite varieties. They can be produced both in cross &self-pollinated crops species.They are the only possible means of exploiting heterosis in self-pollinated species, as open-pollinated, synthetic&composite varieties are not possible in them. Hybrid varieties are maintained in the form of their parental inbreds, which are grown in isolation &subjected to be sibmating.This insure that the genetic constitution of a hybrid variety does not change with time, except due to some spontaneous mutation. In many self-pollinated crops, hybrid varieties yield 25-30%more than the pureline varieties.

Demerits of Hybrid varieties : 

Demerits of Hybrid varieties Farmers have to use new hybrid seed every year.They cannot produce their own seed. Hybrid seed production requires considerable technical skill. The exploitation of full potential of hybrid varieties requires an adequate supply of irrigation water & fertilizer,and control of weeds,diseases & insect pests.Many farmers are unable to ensure a timely application of these essential inputs. In most cross-pollinated species,the requirements of isolation are rigid and ordinarily difficult to fulfil,except on large farms. The amount of hybrid seed required to cover the entire area under any crop appears to impossible to produce with our present seed production set-up.

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