O efeito do gene RHG5 na reprodução de Heterodera glycines raça 6

Abstract

The soybean crop has great representation for Brazilian agriculture. Brazil is now the world's largest producer of this oilseed. Among the various factors that negatively affect crop productivity, the soybean cyst nematode (Heterodera glycines) stands out due to its high potential for damage, wide dissemination, and wide genetic variability. Among the alternatives for controlling this pathogen, the most efficient strategy is the use of resistant cultivars. Obtaining these is a complex activity as it may involve recessive allelic action genes that are difficult to select. The most used genes are Rhg1 and Rhg4. Other genes such as Rhg2 and Rhg5 have gained prominence as a possible source of resistance to cover a greater spectrum of races. Thus, the objective was to study the effect of the Rhg5 gene on the reproduction of H. Glycines race 6, in populations of soybean segregants. Crosses were performed between contrasting cultivars. Populations were genotyped, through the selection of polymorphic SNPs, and phenotyped for reaction to soybean cyst nematode – race 6. The assay was conducted in a greenhouse with an enlarged block design. The progenies were sown in tubes, and after 7 days they were inoculated with 4000 eggs + J2 of Heterodera glycines race 6. At 15 days after emergence, leaf discs were collected for DNA extraction and genotyping. Thirty days after inoculation, the roots were collected, and the females were extracted and counted for later classification of individuals. The phenotypic data were adjusted by a mixed generalized linear model associated with the Poisson distribution with a logarithmic activating function, and the classification of the phenotypic groups was given by the genotypic value of each individual. Six candidate primers were selected for association with race resistance phenotype 6. In all studied primers, there was no exclusive association of a nucleotide with a single phenotypic class, which did not allow the discrimination of phenotypic groups.