Abstract
In several regions of the world, low productivity in this crop is attributed to several factors including poor understanding of the genomic complexity of important traits associated with fruit quality and yield. Therefore, genome wide association analysis was performed for important traits using simple sequence repeats (SSR) markers. Significant variation was recorded for all the studied traits in 78 cucumber genotypes under two environments (open field and net house) which indicated that the constituted association panel was suitable for association mapping. Genotyping was done using 60 highly polymorphic SSRs. By performing genome scanning out of 60 SSR markers, using mixed linear model (MLM) approach 4 and 6 markers explained an average of 23.93% and 17.37% of the trait variation under net house and open field condition, respectively. Based on MLM approach two markers on 3rd chromosome (UW084942) and 4th chromosome (UW062953) found to be associated with the average fruit weight (g) under both net house and open field condition. Population structure analysis revealed four distinct sub-populations that corroborated with the geographical origin as well as fruit quality and quantitative traits. The four sub-populations (A–D) had fixation index percentage equal to 24.35 29.48, 37.17 and 8.97 respectively, supporting the existence of moderate population structures. Therefore, the extensive phenotypic and genotypic characterization, population structure, and markers associated with important traits provided in this study will facilitate marker assisted improvement programs in cucumber.
Highlights
Cucumber (Cucumis sativus L. 2n=2x=14) is one of the most important member of the family Cucurbitaceae
Maximum and mean values of earliness and yield traits studied under net house (8 traits; 1 season mean) and open field condition (10 traits; 2 seasons mean) are given in the table 1 and
The superior performance for earliness and yield traits were recorded under net house grown crop compared to open field condition
Summary
Cucumber (Cucumis sativus L. 2n=2x=14) is one of the most important member of the family Cucurbitaceae. As a result of continuous selection on the basis of local preferences, a large number of landraces and feral forms have been accumulated in different growing regions throughout India. Most of the commercially important traits of cultivated crops are quantitatively inherited and genes responsible for inheritance of these traits are hard to detect. Cucumber has a narrow genetic base with 3–12% polymorphism (Staub et al 2005; Yang et al 2013). Cucumber is considered as a model plant for genetic research because of its smaller genome size (367 Mb), rich diversity of gene expression and short life cycle (Ren et al 2009). A large number of SSR markers from whole genome sequences have been developed (Cavagnaro et al 2010; Ren et al 2009). Draft genomes of three cucumber lines (‘9930’ ‘Gy14’ and ‘B10’) are available and they are instrumental in understanding the structure and organization of cucumber genome (Yang et al 2013)
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