Abstract
ABSTRACT The angular leaf spot (ALS), caused by the fungus Pseudocercospora griseola, is one of the most notable diseases of common beans (Phaseolus vulgaris). The most effective strategy to control ALS is quantitative disease resistance provided by major and minor genes. One breeding strategy for obtaining lines with durable resistance to P. griseola is a recurrent selection that aims to gradually assemble favorable alleles. In this study, common beans were artificially inoculated with P. griseola and grown in a greenhouse under a recurrent selection program that aims to accelerate the breeding cycle and assimilate resistant conferring genes per generation. From the initial population, three cycles of evaluation, selection, and intercross were carried out in a greenhouse and the most resistant plants were phenotypically selected. Plants at the V2 stage were inoculated with an isolate of P. griseola, race 63-63. Selected plants were transplanted into pots and intercrossed to reap the next cycle of selection. Progenies obtained from the base population (C0) and subsequent cycles (CI, CII, and CIII) were assessed for the degree of the symptoms for ALS under greenhouse and field conditions. The rate of genetic progress per breeding cycle was - 14.8% and - 5.3% for the plants grown in greenhouse and field, respectively. Artificial inoculation with P. griseola allowed three recurrent selection cycles per year, signifying a promising method to obtain ALS-resistant common bean lines in a short period.
Highlights
Pseudocercospora griseola (Sacc.) Crous & Braun causes one of the most prevalent diseases of common bean, the angular leaf spot (ALS)
Librelon et al (2020) have suggested that artificial inoculation of P. griseola in a greenhouse can lead to a genetic gain in the recurrent selection program
The present study proposes an artificial inoculation of the pathogen and early assessment of ALS at the V2 stage of common bean plants
Summary
Pseudocercospora griseola (Sacc.) Crous & Braun causes one of the most prevalent diseases of common bean, the angular leaf spot (ALS). A recurrent selection program, aimed at raising ALS-resistant plants, has been carried out at the Universidade Federal de Lavras in partnership with Embrapa since 1998 (Nay et al, 2019; Lemos et al, 2020; Librelon et al, 2020). This program has shown significant genetic gains over the years, but since progenies persist exhibiting variability, the breeding program has continued (Rezende et al, 2014; Nay et al, 2019). This study did not calculate the scope of genetic progress (Librelon et al, 2020)
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