Caracteres agronômicos e trocas gasosas na identificação de genótipos de batata tolerantes ao calor

Abstract

Rising temperatures affect not only human comfort and well-being, but most agricultural production, reducing yield, performance and product quality of the various cultivated crops. The potato crop is one of them, as it represents one of the major crops and one of the most important for human consumption. On the other hand, this crop is greatly affected by the effects of heat mainly in countries of the tropical climate, since its initial process of improvement was started in temperate countries. The objectives of this work were to observe the behavior of potato clones to heat stress and without heat stress conditions on tuber yield and on the performance of gas exchanges, in order to identify characters in the physiological responses of the plants that associate the yield of the genotypes with the heat tolerance. The experiments were carried out at the experimental farm of the Universidade Federal de Lavras - UFLA and consisted of two experiments arranged in a complete randomized block design, with 25 treatments and three replications. The first one was carried out during the harvest with heat stress and the second in the harvest without heat stress. Agronomic evaluations were performed on tuber yield, as well as measurements of foliar gas exchanges at four times during the crop cycle, at 40, 55, 70 and 85 days after planting (DAP). In the end, indices for identification of genotypes were also evaluated regarding heat tolerance and stress sensitivity. Potato genotypes, under stress conditions (average temperatures of 25,1 ° C and maximum of 37,5 ° C), had high reductions in agronomic performance regarding total yield, yield of large tubers and number of tubers. They also presented high rates of physiological disorders and reduction in tubers dry matter content. The physiological processes were quite affected among the two harvests. In the harvest with heat stress were observed increases in the photosynthetic rate of the plants, as well as increases in stomatal conductance and transpiration rates. The efficiency of the physiological processes evaluated through water use efficiency, intrinsic water use efficiency and carboxylation efficiency, however, was significantly higher in the stress-free condition. Through tolerant and sensitive clones selected from the selection indices and graphical analysis, it was possible to observe the behavior of the genotypes along the crop cycle. Significant differences in physiological responses in different clones were observed at the end of the crop cycle from 70 to 85 days, while photosynthesis and intrinsic water use efficiency were the physiological parameters with the highest association with agronomic traits under stress-free and heat stress conditions.