Viabilidade da condução de três ciclos de seleção recorrente visando à resistência a Pseudocercospora griseola no feijoeiro

Abstract

The objective of this work was to evaluate the efficiency of the artificial inoculation of Pseudocercospora griseola in greenhouse, in a recurring selection program aiming at the resistance to the angular leaf spot in bean. The base population was obtained from the sample of seeds from the XVIII cycle of a recurring selection program, using artificial inoculation of P. griseola. From this population, three assessment, selection and recombination cycles were conducted in greenhouse, phenotypically selecting the most resistant plants from the 30 progenies were obtained in each cycle. The plants in stage V2 were inoculated using an isolate from race 63-63 of P. griseola. The selected plants were transplanted to pots and intercrossed to originate the next cycle. The progenies obtained in each cycle were advanced in field until generation S0:2 . The progenies obtained from the base population (C0) and from the subsequent cycles (CI, CII and CIII) were assessed regarding the severity of the angular leaf spot , in greenhouse and in the field. Cultivars Carioca MG (susceptible), Perola (intermediate) and line MA III-16,159 (resistant) were used as witness. Gain productivity was also evaluated. Genetic and phenotypic parameters were estimated to characterize the severity of the angular leaf spot, as well as the coincidence and genetic progress, in greenhouse and in the field. All evaluated progenies prese nted good resistance level to the angular leaf spot. Taking as reference the mean of cycle 0, the gains were of -14.83% and -5.3%, for greenhouse and field, respectively. Based on the results obtained, it is possible to infer that the recurring selection in greenhouse, with the artificial inoculation of P. griseola, using only one race of the pathogen, selects especially genes of greater effect. The use of artificial inoculation of P. griseola allows the conduction of three recurring selection cycles per ye ar, making it a promising method for obtaining resistant lines. However, to optimize the employment of recurring selection in greenhouse, and select especially genes for horizontal resistance, therefore a durable resistance, it is necessary to associate gr eenhouse selections with artificial inoculation, and field selection with the natural occurrence of P. griseola.