Abstract
Phytophthora capsici Leonian, the causal agent of foliar blight, root rot, fruit rot and crown rot syndromes in squash (Cucurbita moschata), is a devastating pathogen worldwide. Resistance to Phytophthora crown rot in University of Florida breeding line #394-1-27-12 (C. moschata) is conferred by three independent dominant genes (R1R2R3). Availability of DNA markers linked to R1R2R3 genes would allow efficient breeding for Phytophthora crown rot resistance through marker-assisted selection (MAS). The goal of the current study was to identify quantitative trait loci (QTLs) associated with resistance to Phytophthora crown rot in an F2 population (n = 168) derived from a cross between #394-1-27-12 (R) and Butter Bush (S) using QTL-seq bulk segregant analysis. Whole-genome resequencing of the resistant (n = 20) and susceptible (n = 20) bulk segregants revealed ~900,000 single nucleotide polymorphisms distributed across C. moschata genome. Three QTLs significantly (P < 0.05) associated with resistance to Phytophthora crown rot were detected on chromosome 4 (QtlPC-C04), 11 (QtlPC-C11) and 14 (QtlPC-C14). Several markers linked to these QTLs are potential targets for MAS against Phytophthora crown rot in C. moschata. The present study reports the first QTLs associated with Phytophthora crown rot resistance in C. moschata.
Highlights
Disease epidemics caused by the oomycete Phytophthora capsici Leonian are a major challenge for squash (Cucurbita pepo L., C. moschata Duchesne, and C. maxima Duchesne) growers worldwide[1]
Extensive efforts have led to identification of sources of resistance to Phytophthora crown rot in unimproved germplasm of Cucurbita
The goal of the current study was to use QTL-seq to identify QTLs associated with resistance to Phytophthora crown rot in an F2 population derived from a cross between the resistant breeding line #394-1-27-12 and Butterbush, a susceptible butternut-type cultivar
Summary
Disease epidemics caused by the oomycete Phytophthora capsici Leonian are a major challenge for squash (Cucurbita pepo L., C. moschata Duchesne, and C. maxima Duchesne) growers worldwide[1]. Current strategies for managing P. capsici in commercial squash production rely heavily on chemical fungicides, existence of fungicide-resistant P. capsici isolates in major squash growing regions has rendered many chemicals ineffective for the control of the pathogen[3,4,5] Cultural management practices such as crop rotation and soil-water management focus on inoculum reduction or avoidance, but are not solely effective, under heavy disease pressure[6]. The goal of the current study was to use QTL-seq to identify QTLs associated with resistance to Phytophthora crown rot in an F2 population derived from a cross between the resistant breeding line #394-1-27-12 and Butterbush, a susceptible butternut-type cultivar
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