Inter-allelic interactions in the inheritance of physical-quality traits in peanut (Arachis hypogaea L.)

Genetic models presume the absence of inter-allelic interactions (epistasis), while estimating components of genetic variation, may lead to biased estimates. Genetic control of physical quality traits in peanut and role of epistasis was studied following a triple test cross mating design. The experimental materials consisting of 27 progenies produced by crossing nine inbred lines belonging to both Spanish and Virginia botanical groups with three testers (TAG 24, TMV 2 NLM, and their F1) were evaluated in a replicated randomized complete block design. The data on parents, F1s and three-way crosses were collected for 10 physical-quality traits of pods and kernels following standard procedures, and analysed to detect epistasis. Inter-allelic interactions were detected for shelling outturn, 100-pod weight, count, 100-seed weight, sound mature seeds, pod length, seed diameter and ratio of seed length to seed diameter using F or t statistics. For pod diameter and seed length, epistasis could not be detected by both the tests, and in the expression of these two traits additive gene action was very important. Partitioning of total epistasis to its component parts indicated presence of both additive additive (i) type and additive dominance (j) + dominance dominance (l) type inter-allelic interactions for 100-seed weight with the preponderance of the former indicating that it can be effectively exploited. Inheritance of 100-pod weight was controlled by i type of inter-allelic interactions, shelling outturn was controlled by j+l type. The findings suggest that improvement in physical-quality traits, especially pod and seed size can be achieved through conventional breeding, but it would be necessary to delay the selection process until maximum frequency of homozygous loci is achieved to exploit i type epistasis.