MOLECULAR MARKERS ASSOCIATED WITH RESISTANCE TO MACROPHOMINA PHASEOLINA (TASSI) GOID. IN COMMON BEAN

Charcoal rot [Macrophomina phaseolina (Tassi) Goid.] causes significant yield losses to common bean (Phaseolus vulgaris L.) in Mexico when drought and high temperature stress occur. In this work, in vitro reactions to M. phaseolina in the cotyledons of 100 F₂ plants derived from the cross BAT 477 (resistant) x Pinto UI-114 (susceptible) and the parents were measured, and AFLP molecular markers associated with BAT 477 M. phaseolina resistance were found. The AFLP analysis consisted of selective amplification using 20 EcoRI + 3/MseI + 3 selective oligonucleotides. Charcoal rot resistance is controlled by two dominant genes with double recessive epistatic effects. AFLP analysis produced 294 polymorphic amplified products. Using the 130 least distorted loci a linkage map was produced that included eight LG where 30 loci were mapped. A possible quantitative trait locus (QTL) was found at linkage group 1 (LG1) showing logarithm of odds (LOD) = 5.11 (critical LOD for genomic amplitude level = 7.23 and critical LOD for chromosomal amplitude = 5.5 based on permutation tests). A permutation test for single markers by regression analysis produced a critical value F = 14.76. However, the locus with the highest F was ATA/AGT-19 (F = 9.329, P = 0.0029). In conclusion, BAT 477 resistance to charcoal rot was controlled by two dominant genes with double-recessive epistasis and one possible QTL at LG1 was detected in BAT 477. Better understanding of charcoal rot resistance will provide improved protection for common beans in the future.