Incorporating resistance to Xanthomonas campestris pv, phaseoli into bean using the latent period as a resistance marker

Abstract

High levels of resistance to Xanthomonas campestris pv. phaseoli (Xcp) were developed in the common bean (Phaseolus vulgaris L.) by intercrossing genotypes having moderate levels of resistance. This was accomplished by using a modified backcross method. Screening for resistance was based on the length of the latent period for seedlings inoculated in the primary leaves, via the multineedle wounding method, and incubated in a 29° C controlled growth chamber. Field and greenhouse screening was conducted under tropical conditions with Xcp strains from Puerto Rico. Selected lines were incorporated into the crossing program. Homozygosis of the best lines was increased through greenhouse and field planting for six summer seasons. Resistance was reconfirmed by inoculation of the lines with X. campestris pv. phaseoli, vignicola and glycines under controlled conditions. Three determinate and two indeterminate germplasm lines in the F₈ generation, resistant to bacterial blight, were released as an outcome of this research.