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

Abstract

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.

A Major Effect Gene Controlling Development and Pathogenicity in Botrytis cinerea Identified Through Genetic Analysis of Natural Mycelial Non-pathogenic Isolates

“…The 7 mycelial isolates non-pathogenic on V. vinifera leaves were also unable to infect P. vulgaris leaves. Isolate B116 did infect bean leaves, although it caused much smaller lesions in this host than the aggressive field isolate B448 ( Acosta Morel et al, 2019 ) ( Figure 1 ). This B448 isolate sporulates and produces numerous sclerotia when cultured in synthetic solid media in dark conditions and resembles very much the phenotype of the reference isolate B05.10.…”

“…We have previously identified four B. cinerea isolates, B217, B371, B459, and B471, unable to infect V. vinifera leaves and displaying a mycelial morphotype. In addition, a fifth isolate non-pathogenic on V. vinifera leaves was purified which sporulated profusely, B116 ( Acosta Morel et al, 2019 ). In order to increase the number of natural isolates altered in pathogenicity, we extended the physiological evaluation of our field isolates collection with 170 additional isolates.…”

“…They form part of the collection of field isolates maintained by the CIALE (University of Salamanca, Spain). They were sampled and purified as described previously ( Acosta Morel et al, 2019 ). B. cinerea isolates were routinely grown on MEA plates and incubated at 22°C under permanent darkness or permanent light conditions or under a 16 h photoperiod (light generated by Cool White Osram L 36W/840 fluorescent bulbs).…”

“…Inoculations and evaluation of differences in virulence in V. vinifera variety Tempranillo leaves were carried out using a mycelium plug based inoculation system in non-wounded leaves as described previously ( Acosta Morel et al, 2019 ). The ability to infect P. vulgaris leaves was analyzed using whole plants.…”

“…We are interested in the characterization of the local populations of B. cinerea in the vineyards of Castilla y León (Spain). In the course of the analysis of field isolates from different geographic origins large differences in virulence were observed among isolates ( Acosta Morel et al, 2019 ). In this work, we extend our collection of natural isolates altered in pathogenicity and perform a genetic and genomic analysis of their differences.…”