Anthracnose susceptibility for grapevines with resistance loci to downy and powdery mildew in Southern Brazil

Anthracnose, downy and powdery mildew are the principal fungal diseases of grapes in tropical and subtropical regions. The pesticide active ingredients that control downy and powdery mildew diseases provide some protection against anthracnose attack. The release of varieties with resistance alleles to downy and powdery mildew results in less pesticide use that can increase anthracnose attack. Thus, the present work aimed to evaluate anthracnose susceptibility of genotypes with resistance loci to downy and powdery mildew under Southern Brazilian conditions. Genotype susceptibility was tested, as well as the influence of the environment (location and crop season) on increased susceptibility to anthracnose infection. To accomplish the objective, a trifactorial design was established that included 20 genotypes, two locations, and two crop seasons. Anthracnose incidence and severity were evaluated under natural infection in the field. Temperature around 16 °C and relative humidity at 84 % increased susceptibility to anthracnose infection compared to temperature around 20 °C and relative humidity at 75 %. All tested genotypes with resistance alleles to downy and powdery mildew presented symptoms of anthracnose. 'Baron', 'Cabernet Cortis' and 'Calardis Blanc' showed the least susceptibility to anthracnose, whereas 'Aromera', 'Felicia', 'Gf.2004-043-0004' and 'Gf.2004-043-0021' were the most susceptible and bore symptoms of anthracnose. Other genotypes showed variable susceptibility during the evaluation period, depending on environmental conditions. Overall, all interactions among the three tested factors were highly significant