Abstract
The soilborne pathogen Ralstonia solanacearum is the causal agent of bacterial wilt (BW), a major disease of pepper (Capsicum annuum). The genetic basis of resistance to this disease in pepper is not well known. This study aimed to identify BW resistance markers in pepper. Analysis of the dynamics of bioluminescent R. solanacearum colonization in reciprocal grafts of a resistant (BVRC 1) line and a susceptible (BVRC 25) line revealed that the resistant rootstock effectively suppressed the spreading of bacteria into the scion. The two clear-cut phenotypic distributions of the disease severity index in 440 F2 plants derived from BVRC 25 × BVRC 1 indicated that a major genetic factor as well as a few minor factors that control BW resistance. By specific-locus amplified fragment sequencing combined with bulked segregant analysis, two adjacent resistance-associated regions on chromosome 10 were identified. Quantitative trait (QTL) mapping revealed that these two regions belong to a single QTL, qRRs-10.1. The marker ID10-194305124, which reached a maximum log-likelihood value at 9.79 and accounted for 19.01% of the phenotypic variation, was located the closest to the QTL peak. A cluster of five predicted R genes and three defense-related genes, which are located in close proximity to the significant markers ID10-194305124 or ID10-196208712, are important candidate genes that may confer BW resistance in pepper.
Highlights
The soilborne pathogen Ralstonia solanacearum is the causal agent of bacterial wilt (BW), a disease that leads to severe global crop losses in the family Solanaceae [1,2,3,4]
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SLAF-Bulked segregant analysis (BSA) combined with quantitative trait locus (QTL) mapping identified a major BW resistance QTL, qRRs-10.1, on chromosome 10 of the pepper line BVRC 1
Summary
The soilborne pathogen Ralstonia solanacearum is the causal agent of bacterial wilt (BW), a disease that leads to severe global crop losses in the family Solanaceae [1,2,3,4]. It starts extensive colonization and spreads to the aerial parts of the infected plant along the vascular system, blocking the water flux from root to shoot, causing severe wilt symptoms [3,5]. Resistance breeding is considered the best strategy for the management of this devastating soilborne disease [11]; only a few pepper lines are resistant to BW. Root and collar colonization by R. solanacearum after root-dip inoculation is not prevented in BVRC 1, leading to questions about the host–pathogen colonization dynamics in graft combinations of resistant and susceptible peppers
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