QTL Analysis of Late Blight Resistance in a Diploid Potato Family of Solanum spegazzinii x S. chacoense

Several quantitative trait loci (QTL) for resistance to late blight have been reported in diploid potatoes. The diploid wild potato species Solanum chacoense possesses a high degree of horizontal resistance to late blight. In the present study, we report on QTL mapping for late blight resistance in a diploid mapping population of 126 F-1 of Solanum spegazzinii (susceptible) x S. chacoense (resistant). The area under the disease progress curve (AUDPC) values for late blight resistance using the whole plant in vitro assay and the detached leaf assay on the mapping population displayed quantitative variation. Out of 64 AFLP primer-pairs combinations and SSR markers, a total of 209 significant AFLP loci were placed onto the 12 linkage group of potato covering a total map length of 6548.1 cM. QTL analysis based on the AUDPC dataset of the whole plant in vitro assay using the interval-mapping option identified two QTL (LOD > 2.5) located on linkage groups IX and X, which explained 14.70 and 3.40% variation, respectively. The present study revealed the presence of potential new genetic loci in the diploid potato family contributing to quantitative resistance against late blight.