Development of fusarium wilt resistant breeding lines of yardlong bean(Vigna unguiculata subsp.sesquipedalis (L.) Verdcourt) variety githika

Abstract

The present study entitled “Development of fusarium wilt resistant breeding lines from yard long bean (Vigna unguiculata subsp.sesquipedalis (L.)Verdcourt) variety Githika was conducted in the Department of Genetics and Plant Breeding, College of Agriculture, Vellayani during 2023-24, with an objective of evaluation of back cross progenies from Githika for fusarium wilt resistance and yield related traits. The research program consisted of 4 main experiments. First experiment involved evaluation of 35 BC2F1 lines resistant to fusarium wilt developed in the concluded Ph.D project Shahiba, (2023) for yield and related traits of the recurrent parent Githika and 10 lines with maximum morphological similarity with Githika was selfed to produce BC2F2 seeds.This experiment was done in a completely randomized design (CRD) with 2 replications. Evaluation of biometric as well as quality parameters in the 35 BC2F1 lines showed significant variations. High heritability along with high genetic advance was observed for all the characters studied except days to 50% flowering. In experiment 2, a total of 74 BC2F2 seedlings from the 10 selected BC2F1 lines were artificially screened for fusarium wilt resistance during the seedling stage. The pathogen associated with fusarium wilt in yard long bean was subcultured from the already isolated and cultured fungal culture plates developed in the concluded Ph.D project Shahiba, (2023). The isolate obtained were mass multiplied in the sand:maize (9:1) medium at 28°C. Soil inoculation method with 10% inoculum of the pathogen multiplied in the sand:maize (9:1) medium was used to produce disease symptoms on artificial inoculation. The scoring for disease incidence was done using the 0-4 scale reported by Senthilkumar (2003). Out of this 74 BC2F2 lines screened, seventy-one were resistant, two were moderately resistant and one was highly susceptible. In experiment 3, the resistant BC2F2 segregants which were in close proximity to the recurrent parent and with a disease score of ‘0’ were backcrossed to produce BC3F1 lines. Out of 217 pollinations, 22 set into pods and about 248 seed set was observed and pod set percentage was found to be 10.13%. In experiment 4, the 11 BC3F1 lines having maximum morphological similarity with the recurrent parent was morphologically evaluated for the 7 biometric characters. This experiment was done in a completely randomized design (CRD) with 3 replications. Analysis of variance revealed a significant variation among the lines for 7 biometric characters. High phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was observed for pod yield per plant and moderate PCV and GCV were observed for number of pods per plant, pod weight and number of seeds per pod. High heritability along with high genetic advance was observed in pod weight and pod yield per plant, thereby indicating that these traits are predominant in additive gene action. Moderate heritability along with high Genetic advance was recorded for traits such as number of pods per plant and number of seeds per pod, while high heritability combined with moderate Genetic advance was observed for the trait pod length. The pod yield per plant was positively correlated with number of primary branches per plant, number of pods per plant, pod weight, pod length, number of seeds per pod and was negatively correlated with days to 50% flowering. Path analysis of biometric characters revealed that the pod weight had the highest direct positive effect on pod yield per plant, followed by number of pods per plant. A high positive indirect effect on pod yield per plant was shown by pod weight through number of seeds per pod. From the study, 11 resistant BC3F1 lines BG3 1-4-1, BG3 6-3-4, BG313-6-2, BG3 50-2-3, BG350-2-5, BG3 50-2-6, BG3123-1-1, BG3 123-5-2, BG3 123-5-7, BG3123-5-8 and BG3130-2-4 which were in close proximity to the recurrent parent, Githika was obtained and could be carried forward for further evaluation. The BC3F2 seeds of 11 lines found resistant to fusarium wilt could be used as breeding lines for developing varieties resistant to fusarium wilt along with the traits of Githika through a backcross program.