Resistência de genótipos de cevada à giberela

Abstract

Barley (Hordeum vulgare) is the fourth most cultivated cereal in the world. It is highly vulnerable to the Fusarium Head Blight (FHB), a disease caused by the fungus Fusarium graminearum, of difficult control, because in addition to the low efficiency of fungicides, there are still no resistant cultivars for this disease. The present work aimed at characterizing barley genotypes regarding to: their susceptibility to the FHB; the physiological quality of harvested seeds in response to the chemical control applied on the canopy; the type III resistance and, the pollen viability and genetic stability. Therefore, two experiments were installed, side-by-side, in a greenhouse, at the University of Passo Fundo, in two harvest seasons, 2018 and 2019. The genotypes, of different origins, were distributed in a randomized block design, with three replicates. In both experiments, the genotypes were inoculated with conidia suspensions of F. graminearum and evaluated for their reaction to the fungus considering the latency period, severity, thousand grain weight, hectoliter weight and productivity. In one of the experiments, the genotypes were sprayed with fungicides at different plants’ growing stages, and the harvested seeds were evaluated for their physiological quality regarding their germination potential and vigor. The data were submitted to analysis of variance and the means were compared using the Tukey’s HSD test (P≤0,05). The evaluated genotypes do not differ in regard to their resistance to FHB. The physiological quality of barley seed varies positively in terms of their germination potential and vigor, with the application of fungicides at different plant’s growing stages. A third experiment was carried out in the experimental field of Embrapa Trigo, in 2019, to assess the pollen viability and the reaction of the same barley genotypes to the FHB, in an environment favorable to the disease. The eleven genotypes were sown in two periods, with a 15-day difference between them. In the heading stage, kernels with Gibberella zeae perithecium were distributed on the soil surface. For the genetic stability analysis, ears were collected trhee from each genotype, to assess pollen viability. At the end of the crop’s life cycle, the plants were harvested, threshed and classified according to the commercial classification of barley. The kernels affected by the FHB disease were also quantified and submitted to pathology analyses, to evaluate the incidence of F. graminearum. Genotypes present between 75 and 96% pollen viability. The sowing time influences the severity of the FHB disease; barley genotypes do not differ in resistance to F. graminearum, only for the size of kernels. It is concluded that the evaluated barley genotypes are genetically stable; there is no genetic variability between materials in terms of resistance to the FHB disease.