Resistência de genótipos de soja a isolados de Sclerotinia sclerotiorum em casa de vegetação e câmara de crescimento

Abstract

Diseases are one of the biggest constraints for the successful production of soybeans (Glycine max L. Merrill). In recent years, white mold caused by the necrotrophic fungus Sclerotinia sclerotiorum Lib. De Bary has become very important due to their damage caused mainly by changing environments. The objectives of this study were to evaluate the resistance of soybean genotypes to S. sclerotiorum, verify the effectiveness of different environments in the incubation of soybean plants after the inoculation with the fungus and the resistance and aggressiveness of the isolates. Two experiments were conducted at the Federal University of Uberlândia (UFU) - Institute of Agricultural Sciences, the first in a greenhouse (23-25 °C), between the months from October to November 2014 and the second in growth chamber (± 20 ° C), between January and February 2015. The evaluated soybean genotypes were EMGOPA-316 with partial resistance, M7908RR with susceptibility to the pathogen and 101 lines of Germplasm Development Laboratory at UFU (LAGER-UFU). The first experiment was conducted in a randomized block design and the second was completely randomized, with five repetitions each. The inoculation was performed by straw test method using two isolates of the fungus in the first experiment and only one in the second. The isolates were derived from soybean producing fields in the city of Uberaba Minas Gerais State and Jataí Goiás State. It was evaluated the average lesion size (cm) caused by S. sclerotiorum five days after inoculation. This variable was used for the classification of genotypes for resistance to the pathogen. Data was subjected to analysis of variance, the Scott-Knott test at 0.05 significance, joint analysis and multivariate analysis was subsequently performed. It was found that the most resistant genotype was the EMGOPA-316 which is indicated as standard resistance and the LAGER-29 was the most susceptible being indicated as susceptibility standard. Genetic parameters allowed to verify that the incubation environment of growth chamber and the inoculation carried out with the Jataí isolate was more reliable than the greenhouse. And based on UPGMA and Tocher grouping methods it was found that the genotypes are divergent.