Hybrid breeding

GENETICS & PLANT BREEDING

1. HYBRID BREEDING & ACHIEVEMENTS T. Nivethitha , GPB

2. Hybrid - F1 from crosses b/w 2 P urelines , Inbreds , OPV, clones or other population that are genetically dissimilar . Hybridisation – P rocess of crossing two genetically different individuals to result in a new individual with different traits. Objectives: To create genetic variation . To combine desired characters into a single individual. Combination Breeding Transgressive Breeding Production of Hybrids

3. Steps involved in hybrid seed production Collection and evaluation of germplasm Development of inbreds Evaluation of inbreds Production of hybrid seed

4. Development of inbreds Two methods : Selfing -heterozygous populations Doubling of haploids Various population viz. open pollinated varieties, synthetic varieties or any other heterozygous population can be used for selfing . Progeny of selected plants are grown separately from the selfed seed in the next season. Again selection is made for the superior progeny and selfed . This processes is continue to get superior homozygous inbred.

5. Production of Doubled Haploids Production of doubled haploids leads to homozygosity in a single generatio n after recombination of selected parents . Selection is more efficient for oligogenic or polygenic traits in DHs because the genes are fixed in a homozygous background, limiting dominance genetic variation and segregation. The DH method prevents losses of valuable genetic variations better than the conventional selection method.

6. Steps involved Haploid production Haploid identification Genome doubling

7. Evaluation and Selection of Inbreds Lines

8. Phenotypic evaluation Based on the phenotypic performance of inbreds . Poor performance inbreds are rejected. Highly effective for highly heritable characters. Effective in improving yielding ability of inbreds . Reliable measure of average performance of inbreds of all single crosses. Genotypes after phenotypic evaluation are crossed to tester (OPV) with wide genetic base. Performance of top cross progeny is evaluated in replicated yield trails. Top cross test

9. Single cross method U sed to measure SCA of those inbreds which are selected on the basis of top cross performance. The selected lines are crossed in all possible combinations viz., n(n-1)/2, where n is the number of inbred lines. These single crosses are evaluated in replicated yield trials over several locations for yield performance. The best performing single crosses are identified for release as a variety or for use in the production of double cross hybrids.

10. Production of Hybrid Seed After identification of superior line , hybrid seed is produced. Production of Hybrid seed on commercial scale requires- a)Easy emasculation of female parent b)Effective pollen dispersal from the male parent to ensure satisfactory seed set in female parent. Procedure of Hybridisation : 1 . Selection of parents 3.Emasculation

11. 4. Bagging 5. Tagging 6 . Pollination 7. Harvesting of F1 seeds

12. Emasculation Removal of stamens or anthers or killing the pollen of a flower without the female reproductive organ.  Methods: Hand Emasculation Suction Method Hot Water Treatment Alcohol Treatment Cold Treatment Use of Gametocide Genetic Emasculation Self Incompatibility Male sterility GMS (TGMS, PGMS) CGMS CMS

13. Types of hybrids: Intraspecific Hybrid Interspecific Hybrid Intraspecific hybrid: Single cross A*B Double cross (A*B) *(C*D) Three way cross (A*B)*C Modified Single cross (A*A’)*B Double Modified Single cross (A*A’)*(B*B’)

14. Varietal hybrid V1 *V2 Topcross hybrid V*A Double top cross (A*B)*V A, B, C, D – Inbreds V – Open pollinated varieties A’, B’ – are sister inbreds of A and B. Hybrid varieties – first exploited in M aize.

15. Single cross hybrids In cross pollinated species - cross between two inbreds (A x B), I n self pollinated crops-between two homozygous varieties . Total number of single crosses is n (n-1) / 2 More common in some self –pollinated species than cross – pollinated species. Used for the development of double cross and three way cross hybrid. 

16. Double Cross Hybrid Commonly used in maize and Sugarbeet The rows of female and male parent are planted in the ratio 4:1 in maize . The number of all possible double crosses among selected inbred is calculated by n ( n-1) ( n-2) (n-3) /8 where ‘n’ is number of inbreds involved . Double Top Cross Hybrid: used in maize

17. Top Cross: also known as inbred variety cross , and is used as testing the combining ability of inbreds and not for commercial hybrid seed production Multiple Crosses: A cross involving more than four inbred line . Polycross : Open pollination of a group of selected genotypes in isolation from other compatible genotype to promote random mating among selected genotype.

18. Three Way Cross Hybrid: These hybrids sometimes used in maize, in which single cross is used as female and inbred as male and are planted in the ratio of 2:1. These hybrids produced seed of normal shape and size but the main drawback is the low pollen production efficiency of the male inbred parent . In case of single and three way cross hybrids, the rows of female and male parents are planted in 2:1 ratio. The tassels of female parent are removed and natural cross pollination is allowed. In double cross hybrid , the rows of female and male parent are planted in 3:1 or 4:1 ratio.

19. Interspecific/ I ntrageneric hybrids F 1 progeny between two different species of the same genus rarely used for commercial cultivation, because such hybrids are fertile only in few cases. In cotton, interspecific hybrids between G. hirsutum x G. barbadense G.arboretum x G.herbaceum are fully fertile. Several interspecific hybrids at tetraploid level ( Varalakshmi , Sruthi , HB224 , TCHB 213) and some hybrids at diploid level ( DH7, DH9 ) have been released for commercial cultivation in India.

20. Improving the characteristics of inbred lines Various schemes suggested to improve the existing inbreds : Productivity, disease & insect resistance of inbreds Combining ability of inbreds . The following methods are used- a)Pedigree selection e)Somatic hybridization b)Backcross method f) Somaclonal variation c)Convergent improvement g)Genetic engineering d)Gamete selection

21. Merits

22. Demerits

23. Achievements

24. H ybrids released crops using male sterility system Name of crop Type of cross Name of hybrids released Pearlmillet Single cross MH 179, BK 560 Sunflower Single cross BSH 1, HSFH1 Castor Single cross GCH2, GCH3,GCH4 Sorghum Single Cross CSH1,CSH5,CSH6,CSH9 Cotton Intraspecific H4, H6,H8   Interspecific Varalakshmi , Sruthi Pigeonpea Single cross ICPH 8

25. Largest number of hybrids – Pearl millet , Sorghum followed by Maize, Cotton, Rice, Sunflower…… Indian has pioneered in developing hybrid in both Desi and new world cotton. In Maize , QPM opaque 2 gene, high starch ( Histarch hybrid Makka ), baby corn hybrid HM4 . Recently released single cross hybrids are: HM10, Nithya Shree, Vivek Maize Hybrid 33, Vivek QPM 9

26. In P earl millet : HB3, HB5 these were SCH from CMS line Tift 23A. And yeild upto 7 tonnes per hectare in National Demonstration trials Downy mildew resistant hybrids PHB 10, PHB 11,BJ104 and BK560 Public sector hybrids: Pusa 23, HHB50, and HHB 67.

27. TNAU Released Hybrids Rice: CORH 1 (MGR) – 1994, CORH 2, CORH 3, CORH 4, ADTRH 1 . Maize: COH 1 - 1982, COH 2 ,COH 3 ,COH 4 , COH 5, COH 6,CO H (M)7, CO H ( M)8, CO H ( M)9, CO H ( M)10. Redgram : COH 1 – 1994, COPH 2. Cumbu : X 4, X 5, X 6, X 7, TNAU Cumbu hybrid CO 9, CO(Cu ) H8…

28. Reference Plant Breeding Principles & Methods – B.D. SINGH. Development of Hybrid Varieties in Cross Pollinated Crops – Vipin Kumar Pandey . Hybrid Breeding in Plants – JYOTI VERMA. TNAU AGRITECH PORTAL.