Infectividade de Colletotrichum e resistência do cafeeiro à mancha manteigosa

Abstract

The goals of this research were to verify the susceptibility of coffee seedlings from infected plants with blister spot to Colletotrichum sp; analyzing the reaction of coffee‟s access to the pathogen and identify potential molecular markers involved in the Colletotrichum x Coffee interaction. In the first part of this study, fruits were harvested from plants with and without symptoms of blister spot and they were sowed in trays containing sterilized substrate. In the first trial, we evaluated the percentage of germinated seeds and viable seedlings. In the second one, ten commercial cultivars and one cultivar obtained from plants with blister spot symptoms, were inoculated and assessed for the severity of Colletotrichum sp. In the second part of this study, 30 accessions of coffee were inoculated with Colletotrichum sp. The disease severity was evaluated and it resulted in the Intensity Index of Diseases (IID), where with the genotypes were classified as resistant, moderately resistant, moderately susceptible and susceptible. Furthermore, we estimated the disease progress by the Area Under Disease Progress Curve (AUDPC). We conducted Pearson correlation test for both variables, IID and AUDPC. In the third and last part of this work, we used 24 accessions of coffee previously ranked regarding the reaction to Colletotrichum, as showed in the second part. We carried out DNA extraction from leaves to do the PCR reactions and we used 59 pairs of primers already published in the literature derived from the coffee genome project. There was no difference in seed germination, however, the viability of seedlings were reduced in GOPDs. These showed symptoms of blister spot, necrosis in leaves and hypocotyls, wilting and death. The Catuaí Vermelho (GOPD) was highly susceptible to anthracnose, it presented the greatest AUDPC. Only two accessions were classified as resistant, MG1062 (Iapar 59) and MG0245 (Obatã Tardio). As moderately resistant, there were 11 accessions like MG0225 (Iapar 59 poliespermia) and MG1043 (Sarchimor UFV 349-28). Nine accessions were classified as moderately susceptible and most of them were relative to Timor hybrid. The susceptible accessions were eight, highlighting genotypes from Mundo Novo. There was a high correlation (0.937) between AUDPC and IID, and it allows us to opt for one of them to assessment the resistance. Considering the primers were tested aiming to obtain molecular markers, 43 were amplified and twelve of them showed monomorphic patterns. In the present study, we did not find polymorphic primers which could classify the accessions in different categories.