Selection of tomato accessions resistant to early blight by cluster analysis of disease progress curves

Abstract

The objective of this work was to select accessions resistant to early blight (Alternaria tomatophila) through cluster analysis of the disease progress curves in tomato (Solanum lycopersicum). One hundred and thirty‑four tomato accessions from the Banco de Germoplasma de Hortaliças of Universidade Federal de Viçosa (BGH‑UFV) were evaluated in a randomized complete block design, as well as the susceptible controls 'Débora' and 'Santa Clara'. The plants were inoculated with a mixture of spores from different Alternaria spp. isolates and evaluated regularly regarding disease severity every three days after inoculation, totalizing six evaluations. The logistic model was adjusted to data on early blight severity, and the estimates obtained for final disease incidence (B₁) and rate of disease progression (B₃) were subjected to multivariate analysis of variance (Manova). The means of these estimates, for each access, were subjected to cluster analysis. Twenty‑four distinct groups were formed based on disease‑progress curve clusters, which allowed the identification of the BGH‑2143, BGH‑2235, BGH‑2270, and BGH‑2118 accessions as potential sources of resistance to early blight.