“Map-based molecular diversity analysis and association mapping studies of horticultural traits in cucumber”

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Date
2018
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DIVISION OF VEGETABLE SCIENCE ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Seventy eight diverse genotypes of cucumber (Cucumis sativus L.) collected from different places of India and abroad were evaluated for 10 and 8 horticultural traits under open field and under net house condition respectively from 2015-2016 in Randomized Block Design with three replications. Wide variations for different horticultural traits were recorded. Under both the environments it was found that days taken for first female flower to anthesis and days taken for first fruit harvest were lowest for Gy 421(37.53, 47.78) followed by Gy14 (38.22, 47.52), suggesting early harvesting genotype. High PCV (>20%) and GCV (>20%) were observed for fruit length, fruit length/diameter ratio, average fruit weight and yield per plant. The estimates of heritability were found high (>90%) for average fruit weight followed by vine length, yield per plant, fruit length and for days taken for first fruit harvest. Genotypic correlation coefficients indicate that most of the traits showed positive and highly significant correlation. Based on analysis of 60 SSR markers it was found that a total of 171 alleles were amplified with a mean of 2.85 alleles per locus. PIC values had an average value of 0.363 per marker. The range of PIC was ranged from 0.049 (UW084478) to 0.592 (UW084186). The dendrogram based on SSR marker analysis grouped the 78 cucumber cultivars into ten diverse groups, showing sufficient diversity exist among these germplasms. Principal coordinate analysis with SSR markers revealed that germplasm were uniformly distributed across the two axes in both the plots with first axis explained 10.09% of genetic variation followed by 7.64% explained by second axis. There was significant phenotypic variability which indicated the suitability of these germplasm for association studies. Analysis of Population structure revealed four distinct sub populations that corroborated with the geographical origin as well as qualitative and ‒populations that corr quantitative traits. In GLM approach of marker trait association, a total of 15 and 22 SSR markers were found to be associated under net house and field condition respectively, accounting 16.78–72.65% and 11.24-51.89 % of the phenotypic variation. However, in MLM approach only four and six SSR markers were associated with horticultural traits under net house and open condition respectively, recording 15.87–29.31% and 13.40- 23.30 % of the 125 phenotypic variation. Two markers, UW084942 and UW062953 were confirmed to be associated with fruit weight in both the environment following GLM and MLM model. Utilization of these markers information in marker assisted selection will facilitate rapid improvement of cucumber with respect to important horticultural traits not only in India but also across the globe
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T-9919
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