Genetic Analysis and QTL Mapping of Resistance to Gummy Stem Blight inCucumis sativusSeedling Stage

Abstract

Gummy stem blight (GSB), caused by Didymella bryoniae (syn. Stagonosporopsis cucurbitacearum), is an important disease of cucumber (Cucumis sativus L.) worldwide. To better understand the resistance to GSB in cucumber seedlings, a set of 160 F9 recombinant inbred lines (RILs) and a total of 405 pairs of SSR primers were employed to detect quantitative trait loci (QTLs) conferring the resistance. Genetic analysis indicated that the resistance to GSB in PI 183967 seedlings was quantitative and mainly governed by two pairs of major QTLs and multiple minor QTLs. Six QTLs, gsb3.1, gsb3.2, gsb3.3, gsb4.1, gsb5.1, and gsb6.1, for resistance to GSB in cucumber seedlings were detected. The stable locus gsb5.1 on Chr.5 was repeatedly detected in three seasons. Locus gsb5.1 accounted for the highest phenotypic variation, 17.9%, and was flanked by SSR15321 and SSR07711 within the genetic distance of 0.5 cM. There were 102 candidate genes predicted in the region harboring the stable QTL gsb5.1, of which seven genes were related to disease resistance. These results can provide a good base for further study and molecular markers for fine-mapping the major QTL conferring GSB resistance in cucumber.

The USDA cucumber (Cucumis sativus L.) collection: genetic diversity, population structure, genome-wide association studies, and core collection development

“… 53 ) and gsb5.1 (ref. 55 ) seem to be at nearby regions of the two peaks we identified from GWAS in this study on chromosomes 2 and 5, respectively, which obviously need further investigation to confirm. In addition, a recent report also identified a candidate gene for GSB resistance in melon located on chromosome 4 around 4.0 Mb 57 ; however, it does not appear to reside in syntenic regions 58 with the QTL identified this study.…”

“…var. hardwickii ) accession PI 183967 have been reported with some contradictory results 53 , 55 . Liu et al 55 identified six QTL on chromosomes 3, 4, 5, and 6 ( gsb3.1, gsb3.2, gsb3.3, gsb4.1, gsb5.1, and gsb6.1 ) with gsb5.1 as a major QTL.…”

“…hardwickii ) accession PI 183967 have been reported with some contradictory results 53 , 55 . Liu et al 55 identified six QTL on chromosomes 3, 4, 5, and 6 ( gsb3.1, gsb3.2, gsb3.3, gsb4.1, gsb5.1, and gsb6.1 ) with gsb5.1 as a major QTL. On the other hand, Zhang et al 53 identified five QTL ( gsb-s1.1, gsb-s2.1, gsb-s6.1, gsb-s6.2 , and gsb-s6.3 ) for resistance to GSB in PI 183967 with gsb-s6.2 having the largest effect.…”

Gummy Stem Blight Resistance in Melon: Inheritance Pattern and Development of Molecular Markers

“…However, PCR amplification detected no polymorphism to closely related resistance genes (the nearest R genes of GSB-linked SSR marker and eight previously reported GSB R genes) ( Figure S2 ). After aligning the cucumber GSB-linked QTL areas, 114 genes were found in melon chromosome 9, of which only one was an R gene (MELO3C002928) based on its the synteny with the cucumber R gene Csa5G485190 [ 18 ], which is known to be associated with GSB resistance ( Figure 2 and Figure 3 , Table S1 ). Among 35 R genes on melon chromosome 9, 30 were amplified, including the previously reported R gene MELO3C002928 [ 24 ].…”

“…Comparative genomic analysis revealed that chromosome 5 of cucumber has a syntenic relationship with chromosome 9 of melon [ 16 , 17 ]. A stable quantitative trait locus (QTL; gsb5.1 ) for GSB resistance was also detected on chromosome 5 in cucumber [ 18 ]. Moreover, the second largest cluster of nucleotide-binding site leucine-rich repeat (NBS-LRR) genes has been reported on melon chromosome 9 [ 19 ].…”