Variation in genotype, pathotype and anastomosis groups of Colletotrichum lindemuthianum isolates from Mexico

Abstract

Patterns of variation were determined in anastomosis, pathotype and genotype of Colletotrichum lindemuthianum samples collected from individual plants of common bean cultivars from four locations in the Mexican highlands. In Chihuahua, 22 polymorphic AFLP bands in isolates taken from a single plant identified five distinct genotypes. In Michoacán, nine genotypes were identified based on a total of only six polymorphic bands. Combined cluster analysis of all isolates from individual plants grouped them geographically. In Chihuahua, in isolates from 16 individual plants, only nine genotypes were identified and all samples were found to belong to the same anastomosis group. However, analysis of selected isolates revealed two new pathotypes not reported previously from Chihuahua (races 449 and 467). In contrast, in Michoacán all 13 isolates from individual plants were found to have distinct genotypes, and in Mexico State only two pairs of isolates among 20 samples had identical genotypes. Although no pathotype variation was determined, five anastomosis groups were identified in Michoacán and three in Mexico State. These results suggest that patterns of variation in genotype and anastomosis groups are complex in the different locations sampled, and that no strong relationship exists between genotype, pathotype or anastomosis group.

Genetic variability within isolates of Colletotrichum lindemuthianum belonging to race 65 from the state of Minas Gerais, Brazil

“…Based on the clustering of similarity estimates for anastomosis, a high number of anastomosis groups were observed within C. lindemuthianum race 65, however, of the 13 isolates investigated only three (LV58, LV61 and LV73) belonged to the same anastomosis group. Similar results have been reported by Rodriguez-Guerra et al (2003) who observed no pathogenic variability in different isolates collected from the same plant, although there was a great variation in the number of anastomosis groups. These authors pointed out that several anastomosis groups could be identified in natural populations and suggested that this might be a mechanism for the formation of different C. lindemuthianum clonal lineages.…”

Sexual recombination in Colletotrichum lindemuthianum occurs on a fine scale

“…One possible reason for the different levels of genetic diversity observed in each of the populations that we examined is that the pathogen interacts with the different host cultivars at each location and consequently interacts with different genetic backgrounds. In this case, the host diversity would influence the maintenance of the genotype diversity of the pathogen (Rodríguez-Guerra et al, 2003). The differences observed between populations are consistent with the fact that they did not produce compatible crosses, suggesting reproductive isolation between the five populations, which resulted in significant variability between the different sample locations.…”

“…In other words, the populations exhibit gametic equilibrium, suggesting that at some points during the host cycle, the pathogen undergoes sexual reproduction (Rodríguez-Guerra et al, 2003). Sexual reproduction allows for the generation of new combinations of alleles in each recombination cycle, leading to a high level of genetic diversity in the pathogen's population.…”

Common bean germplasm resistant to races 73 and 2047 of Colletotrichum lindemuthianum

“…The high pathogenic variability revealed by C. lindemuthianum, which has not been completely elucidated, is attributed to its parasexual cycle (Rodríguez-Guerra et al, 2004). The pathogen's reproduction mechanism is responsible for continuous resistance enhancement, mainly observed in commercial cultivars, since most of them present monogenic resistance that is easily overcame by emerging races (Rodríguez-Guerra et al, 2003).…”

“…The pathogen's reproduction mechanism is responsible for continuous resistance enhancement, mainly observed in commercial cultivars, since most of them present monogenic resistance that is easily overcame by emerging races (Rodríguez-Guerra et al, 2003). However, among the diverse strategies adopted to control anthracnose, genetic resistance is considered the most efficient and economical (Mahuku et al, 2002).…”