Yield stability of soybean cultivars in response to sowing date in the lower latitude Brazilian Savannah Highlands

Abstract

SUMMARYAcquisition of high-yielding stable cultivars, a major target for breeding, is achievable by repeated trials across different locations and seasons. The hypothesis is whether evaluation of sowing date and season could be used to assess yield stability for tropical soybean, a photoperiod-sensitive plant. Determinate growth cultivars BRSOY-1, BRSOY-2, BRSOY-3, BRSOY-4, BRSOY-5, BRSOY-6, BRSOY-7, BRSOY-8 and BRSOY-9, of early, mid-cycle and late maturity, were tested at six sowing dates in three growing seasons (2005–2008), in Planaltina, DF Brazil. Data on degree days to first flower and physiological maturity, plant and first pod height, and grain yield were analysed. BRSOY-3, BRSOY-5 and BRSOY-7 were the most stable, measured across 18 environments (year×sowing date), demonstrating selection effectiveness. Determinate growth explained low yields in late-sown treatments, as the photoperiod response reduced the reproductive phase. Late cultivars had photoperiod effect confounded with dry spells at the end of the rainy season. Genotypic stability for high yield in soybean is envisaged as a function of maturity group and long reproductive period. Manipulating the response to maturity and introduction of indeterminate growth habit is expected to increase yields across the sowing period, consolidating tropical soybean production. The method could be used for cultivar release and to define selection schemes aiming at recombinants for delayed maturity.