Parasexual recombination in Macrophomina pseudophaseolina and vegetative compatibility reactions in M. euphorbiicola

Charcoal rot is an economically important fungal disease of economically important crops. Several species of the Macrophomina genus, such as M. pseudophaseolina and M. euphorbiicola, may act as the causal agents of charcoal rot. The current study evaluates: a) the diversity of vegetative compatibility reactions in Brazilian isolates of M. pseudophaseolina (totalling 27) and M. euphorbiicola (totalling 3), b) the genetic variability of Brazilian isolates, and c) the occurrence of parasexual recombination in M. pseudophaseolina isolates. In complementation tests, 2 and 18 Vegetative Compatibility Groups (VCGs) were identified for the M. euphorbiicola and M. pseudophaseolina isolates, respectively. Correlations between VCG and the isolates ' geographic origin were not found since most isolates derived from the same localities were grouped in distinct VCGs, demonstrating their genetic variability. Further, RAPD analysis of the isolates did not reveal significant correlations between genotype, geographic location and hosts, since isolates derived from distinct localities or hosts formed the same RAPD group. Heterozygous diploids were produced as fast-growing sectors by heterokaryons formed with M. pseudophaseolina isolates, demonstrating, for the first time, the occurrence of the parasexual cycle in the species, based on molecular and phenotypic evidence. Diploids spontaneously produced paternal segregants and parasexual recombinants, demonstrating that parasexuality is an important mechanism for transferring genetic material in filamentous fungi. Results suggest that parasexual recombination may play an important role in the genetic variability of M. pseudophaseolina and may be the cause for the origin of new pathotypes, which could compromise disease control strategies in crops.

Automated summary

This study evaluates the diversity, genetic variability, and occurrence of parasexual recombination in Brazilian isolates of the economically important fungal pathogens M. pseudophaseolina and M. euphorbiicola. The results suggest that these species have genetic variability and parasexual recombination may be the cause for the origin of new pathotypes.