GENETIC DIVERSITY IN IVY GOURD [Coccinia grandis (L.) Voigt.] GENOTYPES OF NORTH EASTERN REGION BASED ON MORPHOLOGICAL AND RAPD MARKERS
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Date
2014
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AAU, Jorhat
Abstract
An experiment was conducted to study the genetic diversity in ivy gourd [Coccinia grandis (L.) Voigt.] genotypes collected from different parts of Assam and other North Eastern States (Arunachal Pradesh, Tripura and Nagaland) during the summer seasons of 2013 and 2014. The experiment was laid out in Randomized Block Design with three replications at the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat. Morphological characterization of 22 genotypes revealed significant variation among the genotypes. The mean performance of genotypes for quantitative traits revealed that the genotype IG-23 recorded maximum for fruit characters viz., fruit length (8.50 cm), fruit weight (33.62 g) and fruit yield per plant (8.66 kg). Whereas IG-22 exhibited the highest number of primary branches (7.35), fruit width (3.03 cm) and number of fruits per plant (391.83). Promising genotypes were IG-10, IG-18, IG-22 and IG-23. Genetic variability in terms of PCV and GCV were high for yield per plant (27.56% and 23.87%, respectively). High heritability in broad sense combined with high genetic advance was recorded for number of fruits per plant (94.39%, 38.57%) followed by fruit weight (93.36%, 32.61%) which were indicative of preponderance of additive and additive x additive type of gene interaction. The correlation analysis revealed that yield per plant had significant positive correlation with number of primary branches, fruit length, number of fruits per plant and fruit weight. From the path coefficient analysis, it was observed that number of fruits per plant had the highest positive direct effect (1.1928) on yield. Number of primary branches had the highest positive indirect effect on yield via number of fruits per plant (1.1491). The residual effect was 0.1097 which was within a reasonable limit indicating that the characters included in path coefficient analysis were adequate in explaining the variation in ivy gourd.
Genetic diversity using Mahalanobis’s D2 statistic grouped the genotypes into 6 clusters following the method suggested by Tocher. Among the 6 clusters the intra-cluster distance varied from 0.00 to 3.48 and maximum inter-cluster distance was observed between cluster IV and cluster V (7.83). Cluster IV showed desirable values for number of primary branches (6.66), peduncle length (2.27 cm), fruit length (7.10 cm), number of fruits per plant (302.83), fruit weight (28.92 g) and yield per plant (7.55 kg). The most important characters contributing towards divergence were fruit weight (37.23% contribution) followed by number of fruits per plant (30.30%). D2 analysis revealed that the pattern of distribution of genotypes from different locations into different cluster was random. At molecular level, 25 random decamer primers generated a total of 124 amplification products of which 52 bands were polymorphic. Total polymorphism was 41.94%. The extent of polymorphism was higher with RAPD primers such as OPB-08 (83.33%), OPC-01 (71.43%) and OPD-05 (66.66%). The dendrogram showed that UPGMA cluster analysis grouped the genotypes into 4 major clusters. In cluster I, only one genotype i.e. IG-14 was included which was out grouped from the rest of the genotypes. A fairly wide range of Jaccard’s similarity coefficient (0.10 to 1.09) was observed which indicated high level of genetic diversity. Among the nutritional traits, highest protein content (1.41 g/100 g) as well as iron (2.75 mg/100 g) were recorded in IG-22. Ascorbic acid (27.05 mg/100 g) and carotene (189 g/100 g) were found to be highest in IG-18. IG-23 recorded the highest crude fibre content (1.97%) and total ash content (6.78%).
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