Melhoramento genético de arroz de terras altas para condições de baixas temperaturas, visando o cultivo em segunda safra

Abstract

The riceis considered a food of extreme relevance in human nutrition, because it is consumed by half the world's population. As the world's population grows, the consumption of this cereal also increases proportionally andgiven this fact, there will be an increasing demand for research and new discoveries about the rice plant.A promising production system is the insertion of upland rice in succession with soybeans, in the second crop.However, in the second harvest, rice will go through a cold period that can lead to serious problems, such as delayed cycle, increased sterilization rates of the spikelets and, consequently, a drop in production, which is aggravated in the upland cultivation system.Given the above, the research aimed to evaluate the phenotypic performance of highland rice elite lines under different temperature conditions during the rubbery phase.The treatments used were: eight Highland rice elites lines obtained from the Value of Cultivation and Use (VCU) and six different temperature conditions, being 12, 17, 20, 25, 29and 32ºC, totaling 48 treatments.The experimental design was entirely randomized (DIC) with three replicates.The experiment was conducted in a greenhouse and in BODs (Biochemical Oxygen Demand) of the Agriculture Department of the Federal University of Lavras (UFLA).The variables evaluated were: number of days to flowering (NDFL), cycle, plant height (ALT), number of tillers (NP), number of panicles (NPA), number of spikelets per panicle (NEPA), spikelet sterility, and dry (PMSA) fresh (MFA) and mass.For the variables NDFL, cycle, ALT and NEPA, there was a genotypes x temperatures interaction, for the other variables the interaction was not significant.In general, the results showed that the genotypes did not tolerate the low temperatures of 12 and 17 ºC, causing low performance in yield components and 100% grain sterility.The temperatures of 25 and 29 ºC showed the lowest rate of spikelet sterilization. The genotypes CNAx20665-B-6 Trat.81EO,CNAx20658-B-12Trat.73EO,P85-15-CNAx18874-B-5-6Trat.17from Preliminary and BRSMG Caçuladeserve to be highlighted for presenting a high precocity in the temperature range of 20 to 32 ºC.Although the genotypes are not tolerant to the low temperatures of 12 and 17 ºC, the characteristics evaluated at the other temperatures serve as a parameter for choosing the best genotype and enabling the improver to insert it in a hybridization program.