QTL Analysis Of Marketable Fruit Growth Rate In Cucumber(Cucumis Sativus L.)

Marketable fruit growth rates are important traits influencing prematurity and yield in cucumber. Several researches on the traits of affecting prematurity and yield of cucumber have been reported. However, up to now, the growth rates of fruit have received little attention. In this study, Genome-Wide Association Study(GWAS) was conducted to detect the marketable fruit growth rate related genes in the whole genome. Genetic populations(P1, P2, F1, F2, BC1P1 and BC1P2) derived inbred lines ?CG61?(growth slower) and ?CG105?(growth faster) were used for genetic analysis and quantitative trait loci(QTL). The result are as follows:1. GWAS was employed to find marketable fruit growth rates(fruit length growth rate, fruit diameter growth rate and fruit weight growth rate) related genes according to re-sequenced information of core germplasm. Six sites were detected repeatedly in both fruit length growth rate and fruit weight growth rate. And the best GWAS site was SNP2211624 in Chr.5. There was no repeated location detected in fruit diameter growth rate.2. CG61 and CG105 with obvious differences in marketable fruit growth rates, were chosen as parents of genetic populations. Genetic analysis showed that F2 populations obeyed nomal distribution. The traits of growth rate of fruit length, diameter and weight were controlled by one additive major gene plus additive-dominant polygene.3. A genetic map of F2 population was constructed, containing 68 SSR markers and 7 Indel markers. The total length of the genetic map was 493.4cM with the average genetic distance of adjoining markers was 6.58 cM.4. QTL analysis of marketable fruit growth rates was conducted according to the genetic map and identification results of 2015 spring. 2 QTLs of fruit length growth rate were detected in Chr.1, LgrQTL1.1 was considered as the major QTL and it was between two markers Indel4 and SSR20083 with a LOD of 3.89 and contribution rate of 8.7%. 1 QTL of fruit diameter growth rate, DgrQTL2.1, was located in Chr.2. It was between SSR01286 and SSR02634, and the LOD is 4.63, the contribution rate is 12.7%. 3 QTLs of fruit weight growth were detected in Chr.1, the major QTL was WgrQTL1.2. which LOD is 2.6 and contribution rate is 6.3%. Its flanking markers were SSR00045 and SSR19006. The locations of the fruit length growth rate and weight growth rate were partial overlap.5. QTL-seq analysis using F2 population of 2015 autumn detected 3 associated regions of length growth rate and 1 region of weight growth rate in Chr.1. The associated region of diameter growth rate was located in Chr.4. Comparison of located positions of marketable fruit growth rates, total 30 genes has SNP mutations in exons. Csa1M014430、Csa1M015650 and Csa4M540120, which encode protein related to cell division, were found in these regions.