Phenotyping strategies for Elsinoe ampelina symptoms in grapevine (Vitis spp.)

Grapevine anthracnose, caused by Elsinoe ampelina, is a fungal disease with no mapped resistance loci. Thus, this study aimed to evaluate different traits used to phenotype grapevine anthracnose looking for correlated traits and reproducibility during evaluations. Phenotyping was conducted with F-1 siblings segregating for resistance to grapevine anthracnose. The progenies were inoculated with Elsinoe ampelina. Leaves, canes and shoots were phenotyped three times. Real severity and number of anthracnose spots were determined from digital photographs. Complementary, the number of spots was estimated using a scale from 0 to 9 and the severity using standard area diagram (SAD) developed for leaves and shoots. The results revealed positive correlation between real and estimated number of anthracnose spots, and the real and estimated severity. However, the number of anthracnose spots did not correlate with severity. The real data from severity and number of spots presented higher variation than the estimated data based on the SAD and scale, respectively. The evaluation strategy based on number of anthracnose spots showed reproducibility in the three independent bioassays, being the most accurate phenotyping strategy for grapevine anthracnose symptoms.