SELECTION FOR RESISTANCE TO COMMON BLIGHT IN DRY BEAN

Abstract

Common blight (Xanthomonas axonopodis pv. Phaseoli =Xap) is a particularly important problem of common bean (Phaseolus vulgaris
L.) in tropical and subtropical regions. Breeding for resistance is, from an economical and environmental point of view, perhaps the
best control method, since the chemical control is dificult and expensive. This paper reports on the advances and responses of 70 genotypes (seven original parents (C₀), 30 progenitors of the third breeding cycle (C₂), and 33 progenitors of the fourth breeding cycle (C₃)), submitted to a strong infection pressure of this bacterium, under field and greenhouse conditions. The components of resistance were: latent period (X₀), epidemic duration (T_f), area under the curve for disease progress (AUCDP), initial severity (Y₀), and final severity (Y_f). The genetic advance in resistance to common blight after three cycles of recurrent mass selection was 50 %, as a result of a smaller AUCDP, a longer latent period, a shorter duration of the disease, and less initial and final severity. The varieties performed similarly under greenhouse and field conditions.