Distribuição espacial de phytophthora nicotianae e reação de cultivares de cebola ao fungo

Abstract

Onion culture has demonstrated to be highly susceptible to Phytophthora nicotianae with economic damages and high crop costs due to the excessive use of chemical products. The present work ha s as objective to evaluate the spatial dependence of pathogen by Geostatistic and after that, to test the resistance of onion cultivars to this disease under convent ional crop. The experiments were conducted at FCAV/UNESP. Soil samples were collected and processed at the laboratory in relation to pathogen, presence through the count of disks of Sicilian lemon infected of the solution of the soil. Immediately after that, at the same experimental unit, thirteen onion cultivars (Dom Victor, BZ 21; Princesa, Taiko, Óptima, BZ 50, Mercedes, Sunset, Duquesa, Gobi, Sirius, Colina e Superex) were analysed in a randomized blocks design with four repetitions. Weekly evaluations were effectuated, from transplanting to harvest. By spherical isotropic semivariogram model, results demonstrated no spatial dependence, revealing that the area presented uniform distribution of the pathogen. With the mapping incidence by Krigage method in blocks, it was verified higher incidence of fungi between the first three patches of lower place, being sequenced reduced with area declivity. No cultivar evaluated presented resistance to the pathogen. It's detached that - Mercedes, Princesa and Duquesa cultivars are highly susceptible, and the others demonstrated low susceptibility to the pathogen in that first field evaluation.