Portuguese common bean landraces vs. Fusarium oxysporum: a diverse array of resistances (first steps into an unexploited source for resistance breeding)

Abstract

Common bean (Phaseolus vulgaris L.) is the most important food legume worldwide. Portugal holds a very diverse common bean germplasm consisting of landraces that resulted from more than five centuries of natural adaptation and farmer’s mass selection, not yet fully explored in breeding. Fusarium wilt is among the diseases that cause major yield losses in this crop. The agronomical, morphological and molecular diversity observed in this Portuguese common bean germplasm anticipates the presence of diverse sources of resistance not yet explored in breeding and foresees the identification of novel resistance / effector target genes. In order to identify alternative sources of resistance for future allelic diversity breeding exploitation of potential resistance genes, we characterized the resistance to fusarium wilt of 150 Portuguese common bean landraces. Evaluation took place under controlled conditions. Seven-day-old seedlings were inoculated with Fusarium oxysporum f. sp. phaseoli, and symptoms assessed every three days, from 7th to 30th dai, using a visual disease index scale from 1 (healthy leaf) to 5 (dead leaf). These data were used to calculate the AUDPC (area under the disease progress curve) values. Infection responses revealed great variability among landraces, with the identification of an array of diverse sources of resistance. Representatives of the different levels of resistance were selected for a future more detailed molecular characterization of the resistance mechanisms. Once these mechanisms are characterized, this germplasm can be better exploited on common bean resistance breeding.