Métodos de seleção de genótipos de soja para tolerância a chuva na pré-colheita

Abstract

The soybean has been beard problems in seed production of high physiological quality and grain production in many regions of Brazil. These problems are attributed to high temperature and excessive rain in the pre-harvest period. This study aimed to develop a methodology that would allow select genotypes with tolerance to rain excess. The study was divided into four stages. The first phase aimed to the production of plants and uniformity of maturation.Twenty-five genotypes were cropped in Passo Fundo-RS in 2013-14 soybean crop. Five hundred plants were taken from each genotype between R7-R8stages. The second phase consisted in the rain and temperature simulation tests. The plants of the twenty-five genotypes were evaluated under experimental completely randomized designwith three replications, divided in four treatments with different combinations of simulated rain and temperature for a period of three days. The third phase was the determination of seed quality. The samples were evaluated under the weight 1000 seeds, germination test, first germinationcount, accelerated aging, electrical conductivity, dry mass and length of plant and root. The last phase was to evaluate pod characteristics and grain quality. The pods were collected from plants of the twenty-five genotypes and measures relations between pod and beans. Pods were conducting a germination test on roll paper that evaluated damaged grains. All genotypes and treatments showed high vigor seeds. The results showed higher influence of water damaged than the temperatures tested. The germination test was able to identify several genotypes tolerant to excess rain before the harvest. The most sensitive genotypes were DMARIO59i, A4725RG, NS4823 and FPS URANO RR. The rain simulation approach has shown promising results and may identify cultivars with lower and higher tolerance to water excess. There was no correlation between pod/grain relationship, damaged grains and vigor tests.