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sur le développement des zones arides et semi-arides

Titre : Inheritance of shoot and root characters and molecular markers in chickpea (Cicer arietinum L.)

Auteur : Anupama, K

Etablissement de soutenance : Acharya N G Ranga Agricultural University.

Grade : PhD thesis 2001

Résumé
Gene action studies helps the plant breeder in selecting suitable breeding procedure for the improvement of the characters. Recently molecular breeding helped accelerating plant breeding in number of areas like disease resistance, insect resistance and quality characters. The objectives of this study were to investigate the inheritance of shoot and root characters and molecular markers and construction of linkage map in chickpea. The material for investigation comprised of PI, P2, Fi, Fz, BCIPI, BC PZ, F3, and 126 Flo generation random recombinant inbred lines (RILs) of the cross ICCV 2 and IG 62.The results of the present investigation are as follows. * The mean values of FI for all the shoot and root characters studied were closer to the parent JG 62, indicating the presence of dominant alleles for all these characters in JG 62. There was sufficient variability between the parents for the characters studied for their effective utilization. All the shoot and root characters had high heritability estimates. Co-heritability estimates among most of the characters were significant. Days to first flower, days to first pod, days to maturity and number of nodes upto first flower are controlled by both additive and non-additive gene actions. Pod tilling period and total reproductive period are governed by dominance gene action and epistatic gene action. Days to first flower, days to first pod, days to maturity, and podding duration are governed by duplicate epistasis and number of nodes up to first flower are governed by complimentary epistasis. Days to first flower days to first pod and days to maturity are governed by the same major gene (efl-1) through its pleoitropic effect and some other modifier genes. e Number of nodes up to first flower is governed by complementary gene action. The two genes for number of nodes up to first flower were designated as Nfl-1 and Nff-2. Therefore, the genotype for the parent ICCV 2 is nff-lnff-lnff-2nff-2 and that for JG 62 is Nff-INff-INf12Nff-2. Observations recorded on root length and root volume of the parents (ICCV 2 and JG 62) and 126 Flo RlLs at the time of flowering of ICCV 2, JG 62 and at their own respective flowering time has shown that statistically significant variability for root traits exist at the flowering time and it is preferable to record measurements in chickpea at flowering time. Root length has additive and dominance x dominance gene action whereas only additive gene action was significant for root volume. Complementary epistasis operates for both the characters. Duplicate epistasis was found for leaf area, Shoot dry weight, total number of nodes upto flowering and complementary epistasis was found for root dry weight. Leaf let number was governed by a single gene and it is designated as Lln. Correlations between flowring and number of nodes up to first flower as well as between root length and root volume were high. Resistance to fusarium wilt is governed by two recessive genes under homozygous conditions. The digenic ratio of 9:6:1 obtained in F2 generation was confirmed by the F2 progeny and RIL population. The genotype of ICCV 2 is hjhjh2hjhjhj and of JG 62 is H,H,H>H2hjh3 Seventy two percent of the molecular markers segregated in the expected Mendelian ratio (1 : 1) and remaining twenty eight percent markers showed distorted segregation. Different marker classes exhibited varied segregation distortion. MP-PCRs had maximum segregation distortion (60%) and RAPDs had minimum segregation distortion (16%). Fitty-six markers out of 69 segregating markers formed nine linkage groups with seven morphological hait loci, four RAPD, one ISSR, 32 STMS, five MP-PCR and seven RMMFP loci covering 262.8 cM with an average distance of 4.7 cM between two consecutive markers. Linkage was observed for three important traits. Seed size locus was flanked by markers sa14 and TR I, double podding was flanked by TR 1 and TA 14 and one of the two genes governing fusarium wilt resistance was linked to RMMFP marker ta36t146 at a distance of 18.3 cM.  RMMFP, a new technique was found to be efficient in adding new markers. All the four sequenced polymorphic RMMFP loci had microsatellite. The microsatellite flanking sequences had high homology in three cases out of four sequenced markers. In future for the saturation of chickpea intraspecific map either new STMS primers have to be designed or new techniques have to be developed which can detect the polymorphisms even at the intraspecific level and add more markers to get linkages with important genes.

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