QTL mapping of resistance to Thrips palmi karny in common bean

Host plant resistance in common bean (Phaseolus vulgaris L.) is a promising component in an integrated cropping system for managing thrips (Thrips palmi Karny) infestation. This study was conducted to identify quantitative trait loci (QTLs) for resistance to thrips in common bean, using F5:7 recombinant inbred lines (RILs) as a mapping population. The RILs, derived by single seed descent (SSD) of the cross of two Mesoamerican bean lines, BAT 881 and G 21212, were found to show transgressive segregation for thrips resistance in the field. Correlations between damage and reproductive adaptation (RA) scores were significant within and between seasons. The QTLs for both traits were located based on single interval mapping (IM) and joint interval mapping (JIM) analysis using a genetic map constructed with microsatellite and random amplified polymorphic DNA (RAPD) markers. Eight of eleven resulting linkage groups (LGs) were shown to be homologous to chromosomes of the integrated linkage map of common bean. A major QTL for thrips resistance located on LG b06 explained up to 26.8% of variance for resistance in a single season and was named Tpr6.1. The JIM across several seasons revealed various QTLs on LGs b02, b03, b06, and b08, some of which were located at regions of genes encoding for disease resistance. The identification and mapping of thrips-resistance genes is expected to facilitate the development of resistant bean cultivars by using molecular marker-assisted selection.