Penetrance and expressivity of the gene for double podding in chickpea

The double-pod per peduncle trait is known to contribute to increased seed yield in chickpea (Cicer arietinum L.). A cross was made between the single-podded variety ICCV 2 and the double-podded variety JG 62 in 1993. Penetrance and expressivity of the gene for double podding was studied in an F2 population and F10 recombinant inbred lines (RILs) of this cross. Homozygous recessive allele of this gene (ss) governs the production of double flowers and pods per peduncle. Results indicated that the s allele has unstable penetrance and variable expressivity. The penetrance of this allele was 53% for the F2 and 84.5% for the RILs. The ranges for the expression of this trait among the penetrant F2 individuals and the penetrant RILs were 1.1-14.8% and 0.1-33.0%. These were 8.3-30.8% for early sown and 17.1-68.7% for the late sown double-podded parent JG 62. Thus it appears that the allele shows greater penetrance and enhanced expressivity under soil moisture stress. In the F2 the seed yield advantage of the double-podded over the single-podded plants was 18%, whereas among the RILs it was 7%. The increased number of pods and seeds contributed to the higher yield. However, there was a slight decrease in seed size of the double-podded genotypes. An increase in the size of seed may have a role in the decreased penetrance and expressivity of this allele among the double-podded segregants of the ICCV 2 x JG 62 chickpea cross.