Genetic variability of Cercospora coffeicola from organic and conventional coffee plantings, characterized by vegetative compatibility

Screening coffee genotypes for brown eye spot resistance in Brazil

Several researchers have attempted to develop coffee plants that are resistant to brown eye spot (BES); however, no coffee cultivars are resistant to the disease. In the present study, a blend of strains from Cercospora coffeicola was inoculated into 19 Brazilian commercial cultivars and 41 accessions from the Germplasm Collection of Minas Gerais to evaluate the genetic resistance ability within the population and select superior genotypes for the breeding program. After predicting the genotypic values of the estudied material, the evaluations number necessary for selecting genotypes with accuracy and efficiency was determined based on the data of severity to BES. The action of defense mechanisms plant was also investigated by assessing the levels of total soluble phenolic compounds and soluble lignin in contrasting genotypes for disease susceptibility. Based on the results, the accession MG 1207 Sumatra, had an intrinsic genetic capacity to maintain low levels of severity to BES. The genotype MG 1207 Sumatra can substantially contribute to the development of new cultivars, which may lead to the reduced use of pesticides. According to the accuracy and efficiency results obtained, four evaluations BES severity are sufficient to achieve accuracy, providing expressive genetic gains. Finally, the levels of lignin and phenolic compounds were not found to be associated with the resistance of coffee genotypes to BES.

Vegetative compatibility groups and sexual reproduction among Spanish Monilinia fructicola isolates obtained from peach and nectarine orchards, but not Monilinia laxa

The frequency of occurrence of Monilinia fructicola in the Ebro Valley, Spain has increased since its first appearance in 2006, and M. fructicola has displaced Monilinia laxa, the native species which is the main cause of brown rot in peaches in this valley. In order to determine the characteristics that may be related to the displacement, we studied the capacity to generate new genotypic combinations of M. fructicola under laboratory conditions. The morphology and parasitic ability from ten field isolates of M. fructicola and M. laxa collected from three different orchards in the valley, and sampling from five different lesions were studied. Nitrate-non-utilising (nit) mutants were generated in order to test the isolates for vegetative compatibility which was done by assessing their colony growth when cultured singly or in pairs on media that contained different nitrogen sources. For the M. fructicola isolates, five vegetative compatibility groups (VCGs) were identified using the nit mutants and six VCGs were identified when they were grown on potato dextrose agar dishes. In all instances, the vegetatively compatible M. fructicola isolates came mainly from the same orchard. Only one VCG displays the same morphological and competition characteristics. No VCGs were identified among the M. laxa isolates. We did not find any apothecia of M. laxa and M. fructicola isolates in the soil of the three orchards, but we were able to produce apothecia of M. fructicola in the laboratory. Our finding of sexual reproduction and VCGs in the M. fructicola isolates suggests that the genetic variability of M. fructicola could be maintained by sexual and/or parasexual recombination.