Colheita antecipada: uma técnica eficiente para o melhoramento acelerado em soja

Abstract

Plant breeding autogamous programs regardless of the method used for conducting segregating populations require the advancement of many inbreeding generations to obtain a line with all loci of interest fixed, consequently the recommendation of a new cultivar is time-consuming. The time to obtain a new line can be reduced with speed breeding protocols sometimes that can decrease by more than half, the number of years spent from obtaining the segregating population to obtaining line, in some winter crops such as wheat, barley, chickpea, and canola. Speed breeding is a powerful tool to accelerate generations in breeding programs through a set of tools with: adjustment of wavelength and light intensity, optimized temperature, enrichment of CO2 content in the atmosphere, which maximize the photosynthesis rate, in addition to early harvest and germination of immature seeds. Therefore, the objective was to evaluate the viability of soybean seeds in different phonological stages, specifically in stages R6, R7 and R8; estimate genetic and phenotypic parameters associated with the physiological quality of immature seeds in soybean; study on the feasibility of early harvesting to the use of soybean speed breeding. Thirty-two lines of the Value for Cultivation and Use-VCU trial from the soybean breeding program for earliness and grain yield, conducted at Universidade Federal de Lavras -UFLA and selected from Lavras, Ijaci, Itutinga and Nazareno trials at 2018/2019 and 2019/2020 crop seasons were used. Seed quality was measured by means of the germination pattern, seedling length test and emergence test in trays under controlled conditions. These trials were conducted in a completely randomized design with four replications. The characters evaluated were germination of normal seedlings, radicle length and hypocotyl in the germination tests and percentage of emergence in the test in trays. Quadratic and variance components were estimated using free software R. The estimates of the quadratic genotype component and the coefficient of genotypic determination were of low magnitude, showing that seeds physiological quality attributes are highly influenced by the environment. Immature seeds (R6, R7) showed high rates of plant emergence. The average gain in harvest anticipation was 18.5% for the precocity trial and 17% for the productivity trial and the gain in days with anticipation of the harvest was 18 days for the precocity trial and 20 days for the productivity trial. Therefore, up to four inbreeding generations per year of soybean crop In view of the results, it is inferable that with the adoption of early harvest can be performed up to four generations of inbreeding per year in soybean crop in tropical altitude climate conditions, compared to a generation in the field or 2-3 generations if winter nurseries are used.