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082			_a630.28 _bJIT/GE PHD
100			_aJithesh V G
245			_aGenetic analysis of resistance to pod borers and yield in yard long bean(Vigna unguiculata subsp.sequipedalis(L.) verdcourt)
260			_aVellayani _bDepartment of Plant Breeding and Genetics, College of Agriculture _c2009
300			_a218
502			_bPhD
520	3		_aYard long bean [Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt] known as asparagus bean or vegetable cowpea is one of the important vegetable crops grown in Kerala. The long tender pods are highly nutritious containing carbohydrate, minerals, fibre, calcium, phosphorus, iron and many vitamins. Infestation by pod borers Maruca vitrata (Fab.) and Lampides boeticus (Linn.) which are the most important post-flowering pests of yard long bean. This research programme was carried out at the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2006-2008 with the objective to study the genetic basis and inheritance pattern of important quantitative and qualitative characters for resistance to pod borers and yield and to formulate a suitable breeding programme for developing varieties resistant to pod borers and with high yield in yard long bean. Fifty genotypes of yard long bean collected from different parts of Kerala were evaluated adopting randomized block design with three replications. Analysis of variance revealed significant differences for almost all the characters. High GCV was observed for pod length, pod weight, pods per plant, pod clusters per plant, pod yield per plant and 100-seed weight, which indicate that there exists high genetic variability and better scope for improvement of these characters through selection. The characters pod clusters per plant, pods per plant, pod yield per plant, pod weight, pod length, seeds per pod and 100-seed weight had high heritability coupled with high genetic advance. In the present study high heritability and low genetic advance was noted for pod breadth and seeds per pod. Yield per plant showed strong positive correlation with pod weight, pod length, pod breadth, seeds per pod and 100-seed weight. The characters pod weight, pods per plant, 100-seed weight, seeds per pod and pod clusters per plant had positive direct effect. Mahalanobis D2 analysis clustered the 50 genotypes in to nine groups. Maximum divergence was shown between the clusters I and VI. Among the seven characters considered pod yield per plant contributed maximum towards divergence. Selection indices were computed based on yield and yield related traits, five genotypes viz; Trailing Red Poded (L1), NS 621 (L2), Ettumanoor local (L3), Vellayanai local (L4) and Palakkad local (L5) with high yield were selected as female parents in the line x tester analysis. The same fifty genotypes were screened for various damage parameters of pod borers by using randomized block design with two replications. All the damage parameters exhibited remarkable variability with respect to different genotypes. Based on all the damage parameters three genotypes with low plant resistant indices namely Kurappunthara local (T1), Kanichar local (T2) and KMV-1 (T3) were selected as testers in the line x tester analysis. Significant variability was present for different morphological and biochemical characters among the 50 genotypes. High coefficient of variation was noticed for number of trichomes on pod wall. High heritability was noticed for all the characters except crude fibre content. The characters peduncle length, trichome number and protein content of pods showing high genetic advance. In line x tester analysis L1 showed high values of gca effect for pods per plant, seeds per pod, pods per cluster, 100-seed weight and pod length. Among the testers T1 showed significant negative gca effects for all the damage parameters for pod borers. In morphological and biochemical traits line L3 showed positive gca effect for peduncle length, trichome number and protein content of pods but L1 for leaf chlorophyll content. Tester T1 showing positive gca effect for all the morphological and biochemical traits. Based on specific combining ability, the crosses L1 x T1, L3 x T1 and L5 x T1, showed maximum sca for yield attributes and minimum for damage parameters. Many of the crosses showed significant positive sca effects for most of the morphological and biochemical traits. The crosses L1 x T1, L3 x T1 and L5 x T1 exhibited significant positive estimates with high magnitude of yield attributes and morphological and biochemical traits indicating considerable heterosis with respect to the important yield characters. Further the relative and standard heterosis exhibited significance in the negative direction for all damage parameters. This results leads to the conclusion that low relative performance of pod borers larvae in these crosses may be due to its trichome number, protein content of pods, leaf chlorophyll content or fibre content which can offer resistance to pod borers in yard long bean and can form the basis for selection of yard long bean genotypes for pod borer resistance or tolerance. The three superior crosses viz., L1 x T1 (Traling Red poded x Kurappunthara local), L3xT1 (Ettumanoor local x Kurappunthara local) and L5 x T1 (Palakkad local x Kurappunthara local) were utilized for generation mean analysis inorder to detect the gene action with regard to the various traits. Presence of epistasis was tested and subsequently interaction effects viz; additive x additive, additive x dominance and dominance x dominance effects were computed. Significance of scale A and B for most of the characters suggested that the simple additive x dominance model was inadequate for defining the inheritance of these characters. Presence of non-allelic interactions was noticed for days to 50 per cent flowering, primary branches per plant and days to first harvest. Hybridization and selection can be resorted to for improving the character of earliness in this crop. The positive significance of dominance x dominance interactions for pod weight points out that a breeding strategy for improving pod weight should be based on direct selection or hybridization and selection for high pod weight. Presence of all three types of digenic interactions was observed for pods per plant and pod yield per plant. The direction of dominance effect and dominance x dominance interactions suggests the presence of non-allelic duplicate gene action for crop duration, main stem length, pod clusters per plant, pod weight and pod breadth in their expression. For damage measurements additive gene action was significant for all the damage parameters. Additive x dominance gene action was significant for peduncle length. The same direction of dominance gene effect and dominance x dominance interactions is an indication of non-allelic complementary gene action in the expression of this character. For leaf chlorophyll content additive gene action was significant for all the hybrids. The L1 x T1 had positive significance in dominance x dominance epistatic interaction for number of trichomes on pod wall. Predominance of additive gene action in a positive direction was observed for protein content but significant additive x dominance interaction in a negative direction. Additive gene effect was significant for crude fibre content of pods. The positive significance of dominance x dominance interactions points out that a breeding strategy for reducing the fibre content should be based on direct selection or hybridization. The result suggest ample scope of improvement of yield through selection based on the characters pod weight and pod length. The genetic analysis for yield and resistance to pod borers brought to light genotypes which could be used as source of resistance. Two superior crosses in which high yield potential and tolerant to pod borers were identified. Less attack of pod borers larvae to these crosses may be due to high values for any of the two characters namely trichome number or crude fibre content coupled with mechanical barriers with restricts their access to pod surface compared to other crosses. The magnitude and direction of the gene effects underlying the pest damage parameters offers a favourable background for the breeder to develop pod borer resistant/tolerant yard long bean genotypes. Presence of additive, dominance and epistatic interactions for all the characters identified indicated that recurrent selection or recombination breeding can be followed for future breeding programme.
700			_aRadhadevi D S (Guide)
856			_uhttp://krishikosh.egranth.ac.in/handle/1/5810041554
942			_2ddc _cTH