MSc

A research programme was carried at the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during the period 2004-2006 with the object of studying the combining ability variances and the nature of gene action involved in important quantitative and biochemical characters and Fusarium wilt resistance in line x tester progenies of yard long bean.
Based on the previous PG project entitled “Genetic variability for yield and Fusarium wilt resistance in yard long bean (Vigna unguiculata subsp. sesquipealis (L.)Verdcourt)”, five lines having high yield and moderate fusarium wilt resistance and three testers having high fusarium wilt resistance was selected as parents. They were crossed in Lx T pattern and seeds of F1s and parents were laid out in Randomised Block Design with three replications. The fifteen crosses along with their parents were evaluated for mean performance, combining ability, gene action and heterosis based on 22 characters namely, days to 50% flowering, days to first harvest, length of harvest period, crop duration, primary branches per plant, main stem length, pod clusters per plant, pods per plant, pods yield per plant, pods per cluster, pod weight, pod length, pod breadth, seeds per pod, 100 seed weight, fresh weight of roots per plant, nodules per plant, crude fibre content, protein content, peroxidase, polyphenol oxidase and total phenols.
Significant differences among treatments were observed for all characters especially pod yield per plant. The magnitude of sca variance alone was significant suggesting the importance of the dominance gene action in controlling the quantitative and biochemical characters of yard long bean.
Based on the mean performance and gca effects,VS-86 was found to be good general combiner among lines and TVM-1 among testers. The cross, P-1x TVM-1 was found to be promising for main stem length,100 seed weight and polyphenol oxidase and VS-86 x TVM-1 was superior for pod yield per plant based on mean performance, sca effects and standard heterosis. Hence these crosses can be advanced for further trials for developing superior yard long bean varieties.
The pot culture experiments done for screening Fusarium wilt resistant genotypes by artificial inoculation of pathogen revealed that treatments were highly significant. Least mortality was shown by the line P-1, tester TVM-1 and cross VS-86 x TVM-1 followed by Varuvila-2 x TVM-1 and P-1 x TVM-3.
Critical assessment of results suggests ample scope of improvement of yield and fusarium wilt resistance through selection based on combining ability and heterosis. Three superior crosses, VS-86 x TVM-1, P-1 x TVM-1 and Vellayani x TVM-1 were identified which were high yielding and reduced disease incidence. Among these VS-86 x TVM-1 was found to be most superior. Thus the work can be continued with these crosses for evolving varieties superior for yield and fusarium wilt disease resistance.