Identification of Phaeoisariopsis griseola pathotypes from five States in Brazil

Abstract

Due to the increased importance of angular leaf spot of common bean (Phaseolus vulgaris) in Brazil, monitoring the pathogenic variability of its causal agent (Phaeoisariopsis griseola) is the best strategy for a breeding program aimed at developing resistant genotypes. Fifty one isolates of P. griseola collected in five Brazilian States were tested on a set of 12 international differential cultivars in the greenhouse. When inoculated plants showed symptoms but no sporulation was observed, they were transferred to a moist chamber for approximately 20-24 h. After this period of time, if no sporulation was observed, the plants were considered resistant; otherwise, they were considered susceptible. From the fifty-one tested isolates, seven different pathotypes were identified. No Andean pathotypes were identified; consequently, all isolates were classified as Middle American pathotypes. Pathotype 63-31 was the most widespread. Pathotype 63-63 overcame resistance genes present in all differential cultivars and also the resistance gene(s) present in the cultivar AND 277. This fact has important implications for breeding angular leaf spot resistance in beans, and suggests that searching for new resistance genes to angular leaf spot must be pursued.

Aggressiveness of Pseudocercospora griseola strains in common bean genotypes and implications for genetic improvement

“…This demonstrates that it is necessary to obtain cultivars with resistance genes from both gene pools in order to obtain durable resistance (Miklas et al, 2006). The cultivars Cornell 49242 and AND 277 exhibited a moderate level of resistance, in contrast with other studies that have found a high level of resistance in these cultivars (Busogoro et al, 1999;Sartorato, 2002). Therefore, the results of the present study lay emphasis on high aggressiveness of strains used in comparison with the previously cited studies.…”

“…The existence of races is a complication in breeding programs, because cultivars may be resistant to certain races and susceptible to others. P. griseola has great variability, which explains the large number of existing races and the complexity of genetic resistance (Mahuku et al, 2002;Sartorato, 2002;Damasceno-Silva et al, 2008). In addition, in Brazil, most of the strains have been classified as race 63.63, which overcomes the resistance of all the cultivars of the differential group (Balbi et al, 2009;Pereira et al, 2013).…”

Diallel analysis to choose parents for black bean (Phaseolus vulgaris L.) breeding

“…In these studies, the study of inheritance was based on only one parental cross. However, it should be noted that the occurrence of different breeds of angular leaf spot has been reported in the literature (Sartorato, 2002;Sartorato and Alzate-Marin, 2004). Amaro et al (2007) reported a gradation in symptoms among lines considered susceptible to angular leaf spot, and suggested that part of this gradation can be attributed to environmental effects and the polygenic control of the trait, because resistance to angular leaf spot has a complex inheritance.…”

Genetic control of the angular leaf spot reaction in common bean leaves and pods

“…Crous and U. Braun is one of the most important and widely distributed diseases of common bean (Phaseolus vulgaris L.) in producing regions (Sartorato and Alzate-Marin, 2004;Damasceno-Silva et al, 2008). Breeding for resistance has found some difficulties due the great pathogenic variability and absence of genetic control information for some lines (Sartorato, 2002). Information about genetic control is very useful, because it helps breeders to choose the most efficient strategies to make it possible to obtain resistant and productive cultivars.…”