Development of AFLP-derived SCAR markers associated with resistance to two races of southern root-knot nematode in sweetpotato

Abstract

The southern root-knot nematode (SRKN) Meloidogyne incognita severely damages yield and quality in sweetpotato production, and host plant resistance is one of the primary options for SRKN control. Segregation of F1 progeny resistant and susceptible to the SP1 and SP2 races of SRKN suggested that the race-specific resistance of the sweetpotato cultivar “Hi-Starch” is mostly controlled by single genes and that the genes for resistance against each race are closely located. Bulked segregant analysis and subsequent analysis of 86 F1 progeny plants identified nine amplified fragment-length polymorphism markers associated with SRKN resistance and a single linkage map consisting of seven of these markers. Quantitative trait locus (QTL) analysis using the segregating resistance data of the F1 progeny allowed mapping of both a locus with a large effect on resistance to the SRKN race SP1 and another affecting resistance to SP2 to the region around E33M53_090 that was designated as qRmi(t). Two AFLP markers in the vicinity of qRmi(t), E33M53_090 and E41M32_206, were converted to locus-specific sequence-characterized amplified region markers based on their internal and adjacent DNA sequences. These markers might be useful for marker-assisted selection of SRKN resistance in sweetpotato breeding and as a first step to map-based cloning of the responsible QTL(s).