Increasing the efficiency of recurrent selection for angular leaf spot resistance in common bean

Abstract

A common bean (Phaseolus vulgaris L.) breeding program for resistance to Pseudocercospora griseola (Sacc.) Crous & U. Braun (angular leaf spot) using recurrent selection has been conducted since 1998 in Brazil. The selection has been carried out in the field with high natural occurrence of the pathogen. One recurrent selection cycle has been conducted per year. The efficiency of artificial inoculation of P. griseola and early assessment of angular leaf spot severity in common bean progenies of this program were evaluated. For this, 254 and 166 S0:1 progenies from Cycles XVI and XVIII, respectively, were assessed for angular leaf spot severity in field, with natural occurrence of the pathogen and in greenhouse with artificial inoculation of P. griseola. Most progenies showed a high level of resistance to angular leaf spot, indicating the efficiency of recurrent selection. Artificial inoculation of P. griseola in the greenhouse showed promise for the selection of resistant plants in a recurrent selection program allowing breeders to carry out two cycles per year. A scheme was proposed that combined the advantages of early-generation selection with artificial inoculation of the pathogen in greenhouse with the advantages of selection in field with natural occurrence of P. griseola in the dry season, increasing genetic gain per unit time.