Diversidade genética e estrutura de população entre isolados de Corynespora cassiicola no Estado do Amazonas

Abstract

The fungus Corynespora cassiicola is a plant pathogen that has worldwide distribution and has been reported causing disease on leaves, fruits, branches, nematode eggs, and even human skin. In Brazil, this pathogen has already caused serious damage to soybeans, papaya, acerola, and the northern region of the country, this pathogen has great importance in papaya, cucumber and tomato crops. Develop control strategies for a disease depends, among other factors, an understanding of the genetic variability and structure of the pathogen population, these being the goals of this work. We collected 169 isolates from papaya, tomato and cucumber, coming from the cities of Manaus, Iranduba and Presidente Figueiredo, Amazonas state, Brazil, 9 populations totaling.The genetic diversity was analyzed with 8 ISSR primers, 191 polymorphic locus getting, and the polymorphism rate was 100%. The genetic diversity was high in all populations, where the highest genetic diversity index was found in MA2 population (M= 0.43), and the smallest in population of Presidente Figueiredo: PE3 (H = 0.13) and MA3 (H = 0.15). All genotypes showed similar frequencies in the population (E5 = 1.0). Genotypic diversity (G0) ranged from 0.7 to 2.2, and in general was low in all populations, thus proving the absence of recombination. Random association tests detected high levels of linkage disequilibrium, eliminating the null hypothesis (IA> 0), being significant at 1% probability, the highest rates were found in MA1 populations (IA= 6.08) and MA2 (IA= 5:24). Bayesian analysis detected four genetic groups with mixture of genotypes in groups 2 and 3, suggesting gene flow and structure in a host in group 1 (papaya) and 4 (tomato). The population is structured with great distinction between them. MA3 and TO1 populations had higher (θ = 0.27), and the lowest value was found in TO3; TO2 and PE3, PE2 (θ= 0.05). Analysis of AMOVA, the biggest change is occurring within populations (84.3%), while 15.70% is occurring among populations.