Physiological and population genetic analysis of Botrytis field isolates from vineyards in Castilla y León,Spain

Grey mould is reported in the vineyards of Castilla y León, Spain, every year. However, the natural populations of the pathogen have yet to be properly characterized. Vineyards from six wine-producing areas were surveyed in 2002 and 2007, sampling from bunches of grapes with and without symptoms. A total of 283 Botrytis field isolates were selected for physiological and genetic analyses. Botrytis cinerea isolates predominated in the population, although isolates belonging to Botrytis pseudocinerea and Botrytis prunorum were also identified. These two species are recorded for the first time in Spain in this work. In addition, two isolates closely related to Botrytis californica were identified. Physiologically, the B. cinerea population is very diverse, displaying a normal distribution of aggressiveness values in Vitis vinifera leaves, suggesting a quantitative nature for this trait. Several isolates unable to cause infection were identified, most of them belonging to a mycelial morphotype. Population genetic analysis revealed that genotypic diversity is high and that multiple infections of the same bunch of grapes by different genotypes occur frequently. The high genotypic diversity observed, an even distribution of both mating types and the linkage disequilibrium values detected support a mixed mode of reproduction with low levels of clonality. The wine-producing area in which each isolate was collected imposed a low degree of population differentiation, an effect that does not depend solely on the geographic distances but rather on the management practices used by growers and wine producer associations.     

Factors influencing growth,sporulation and virus transfer in <Emphasis Type="Italic">Cryphonectria parasitica</Emphasis> isolates from Castilla and León (Spain)

Biological control with Cryphonectria hypovirus CHV1 of the chestnut blight, caused by the fungus Cryphonectria parasitica, has reduced the impact of the disease in Europe. The virus reduces the virulence of the fungus so that it causes non-lethal cankers, thus enabling the chestnut trees to overcome the disease. The virus can be transmitted horizontally by hyphal anastomosis or vertically to the conidia. In this study, we investigated growth and sporulation of the fungus as well as rates of horizontal transmission of the virus at different temperatures. We used fungal isolates of the vegetative compatibility types (vc types) that are most prevalent in Castilla and León (central northern Spain) to evaluate the effects of fungal strain on the parameters tested. In addition, we infected four isolates of C. parasitica with hypovirus subtypes CHV1-F1 and CHV1-I, to determine the influence of virus subtype on growth, sporulation and virus transfer. We assessed growth of fungal colonies and horizontal transmission of the virus at 15 °C and 25 °C. Colony growth was affected by an interaction between fungal isolates included in vc type EU1 or EU11 and virus at both 15 °C and 25 °C. However, horizontal transmission of the virus was only influenced by the fungal genotype of isolates included in vc type EU1 or EU11, and spore production was only affected by the virus subtype. Vertical transmission was also influenced by the fungal isolate and virus subtype. Growth of the fungal isolates varied depending on the virus subtype with which they were infected. This supports the theory that fungal host and virus subtype influence transmission and dissemination of hypovirulence. The fungal genotype affects colony growth and horizontal transmission of the virus. It is common to expect a good dissemination of the hypovirus with a low vc type diversity but the selection of the best combination of hypovirus and fungal isolate is crucial for the success of biological control not only for small areas but in larger chestnut populations as well.