No abstract

The physiological phenomena of yield barriers in rust resistant groundnut genotypes were studied using growth analysis as a tool. Ten genotypes including four susceptible, three each from partial resistant and resistant categories were subjected for the study. Higher CGR, LAR and LAI during the pod filling and maturity stages in resistant and partially resistant genotypes indicated more partitioning of dry matter to leaf tissues rather than to pods, resulting in poor development of pods and kernels. The evolution of partially resistant varieties in preference to completely resistant ones for cultivation in endemic areas will be more useful.

The cultivated groundnut (Arachis hypoguca L.) suffers from many diseases and pests. The wild relatives of groundnut have been found to he number of diseases. The diploid (2n = 20) wild sp.A.cardenasii was hybridized with the CV. VRI 2 of A. hypogaea (2n-40) and the resultant triploids (2n = 30) were studied. The progenies of the triploid gave rise to triploid, tetraploid and hexaploid (2n = 60) progenies. The tetraploid progenies were again hybridized with the cultivated groundnut and the resultant F, plants were studied. The hybrids exhibited high level of resistance to rust and leafspot diseases which indicated the transfer of genes esferring resistance from A. Cardenasii

The estimated variance due to GCA was higher than SCA indicating the predominance of additive gene action for number of primary branches. The general combining ability effects revealed that ICGS 44 and ALR 2 were the good general combiners for this trait. The specific combining ability effects revealed that none of the direct crosses were good specific combiners; whereas, five combinations of the reciprocal crosses were good specific combiners indicated the importance of maternal effects for this trait. The component analysis indicated that the dominance was in excess of additive component. Intermating of the segregants or multiple crossing are suggested for the improvement of this trait.

Comparison of parents, single crosses and three-way crosses in groundnut revealed that high level of heterotic effects were observed in single crosses for the traits: number of branches, number of mature pods and pod yield. The three-way crosses exhibited heterotic effects for shelling out turn, pod weight and kernel weight. Hence for the improvement of these traits three-way crosses may yield better results than single crosses. The range of mean values was narrow in three-way crosses for four of six traits studied, which suggests that the three-way crosses have more buffering capacity than single crosses.