19. inbred lines development

Dr. NAVEENKUMAR K.L
Assistant Professor

1. Breeding Methods in cross pollinated crops: Inbred Line Development Dr. NAVEENKUMAR K.L Assistant Professor Dept. of GPB UAHS Shivamogga

2. Single cross: when two inbreds , say A & B, are crossed the hybrid/ F1 (A x B) is known as single cross hybrid. When two single crosses, say A x B & CXD, are crossed the resulting hybrid population, (A x B) X (CXD) is known as double cross hybrid .

3. What is inbred line? In allogamous species, a true breeding line obtained by continuous inbreeding/ selfing is called inbred line . or Inbred lines are homozygous genotypes produced by repeated selfing with selection over several generations. An inbred line consists of individuals with the same genotype. It is developed and maintained by repeated selfing of selected plants .

4. Inbred lines are developed from a variable source population. The source population is generally an open-pollinated variety (First cycle inbreds ) or it may be synthetic, a single cross or a double cross (Second , third or fourth cycle inbreds ). Inbreds are usually developed through a suitable system of close inbreeding (6-7 generation of selfing ).

5. Main features of inbred line are given below : It is relevant to cross pollinated species It is true breeding It is homozygous and homogeneous

6. Inbred Line Development in Cross Pollinated Crops The pedigree method of breeding is the most widely used method to develop inbred lines & it is referred to as “ standard method ” when an open pollinated population is sampled. After each selfing desirable plants are selected and self pollinated or sib pollinated. Usually it takes 6-7 generations to attain near homozygosity . The purpose of inbreeding is to fix the desirable characters in homozygous condition in order to maintain them without any genetic change . Inbred lines are developed for the production of Hybrid seeds.

7. There are three operations involved in the production of hybrid varieties- Development of inbred lines Evaluation of inbreds Production of hybrid seed

8. Development of inbred lines There are two methods of developing inbred lines- Selfing of heterozygous populations ( Pedigree method, Bulk method, Single seed descent method, Back cross method) 2. Doubling of haploids

9. Pedigree method is generally practiced in the development of inbreds . PROCEDURE Development of inbred lines:

10. 15 Strategies for the development of inbred lines Director of Maize Research 2010

11. 16 A ×B C ×D G× H E ×F F3 ID advanced Y X ×Y Select productive hybrids F4 to F7 F2 Inbreeding depression study Evaluation in combination breeding biotic and Abiotic stresses X Categorisation seed Pollen parent Maize scheme UAS Dharwad Multiple parent inbred development

12. Doubled Haploid (DH) lines – What are they ? Haploid: an individuals with the gametic chromosome number (n) in its somatic cells. A Doubled Haploid: is a genotype formed when haploid cells (n), i.e. egg or sperm cell undergo chromosome doubling (2n ). The resulting individual is completely homozygous. DOUBLED HAPLOID LINES IN HYBRID BREEDING

13. DOUBLED HAPLOID LINES IN HYBRID BREEDING 19 First Haploid maize - Stadler and Randolph (1929) Spontaneous haploid induction rate in maize of 0.1% and suggested that haploids could be used for line development in hybrid breeding Chase (1947, 1951) COE (1959) - 2.3%, crosses with inbred line stock6. Lashermes and Beckert (1988)- WS14 (W23 ig X Stock6) Geiger and Gordillo , 2009 - inducing lines display high induction rates of 8 -10% .

14. 20 Maize Genetics Cooperation 2010 Stock 6 MHI PHI-1 PHI-2 PHI-3 PHI-4 12.8 14.5 13.0 12.1 7.2 1.2 PHI – Procera Haploid Inducer

15. 21 Haploid identification method Haploid embryos can be selected based on morphological and physiological markers Identification marker is the ‘red crown’ or ‘ navajo ’ kernel trait encoded by the dominant mutant allele R1-nj of the ‘ red color ’ gene R1 Geiger and Gordillo , 2009 kernels with a haploid embryo have a significantly lower oil concentration than those with a diploid F1 embryo Rotarenko et al (2007),

16. 22 CIMMYT

17. Achievements In India inbred lines are developed and released through co-ordinate maize improvement scheme and are designated as CM (Co-ordinate maize), CS (Co-ordinate sorghum) CM-100-199 - Yellow flint CM-200-299 - Yellow Dent CM-300-399 - White Flint CM-400-499 - White Dent CM-500-599 - Yellow CM-600-699 - White 2

18. In India, Hybrid varieties were first to exploit heterosis in maize. The first hybrid varieties in maize were released in 1961, when four double cross hybrids, viz., Ganga1 , Ganga101, Ranjit & Deccan, were released for cultivation. In sorghum, first hybrid CSH1 was released in 1964. In pearl millet , first hybrid HB1 was released in 1964. C astor - GCH3 (1968) C otton - H4 (1970) S unflower- BSH1 (1980) Pigeon pea - ICPH-8 (1991) Rapeseed - PGSH51 (1994) Rice -PRH10 (2001) Tobacco - GTH1 (1996) were first released hybrid varieties