Respostas fisiológicas e agronômicas do feijão (Phaseolus vulgaris L.) ao frio

Abstract

Common bean has great nutritional and economic importance, but their productivity is affected when there are low temperatures in the crop cycle. The objective of this study was to evaluate the physiological and agronomic responses of the comoon bean to cold stress under field conditions and in a controlled environment. In the field, ten common bean genotypes were cultivated at the recommended time and outside the crop zoning, so that they could face cold. Plants were collected each two weeks to evaluate dry matter mass for subsequent calculation of absolute and relative growth rates. The total soluble sugars content was evaluated when the plants were in V4 stage. At the end of the crop cycle the yield components of the cultivars were evaluated. In a controlled environment, the common bean seeds were germinated at optimal and sub-optimal temperatures. Morphological traits and total soluble sugar content of the seedlings were evaluated. Cold stress negatively affected the growth and resulted in the inreasing of sugar content in common bean cultivars, both in the field and in the controlled environment, and significantly reduced the yield components of field cultivars. The increase in the soluble sugar content, alone, is not components for cultivars in the field trial for the greater tolerance to low temperatures. The yield component most affected by low temperatures is the grain mass per plant. BRSMG Madrepérola and BRS Esplendor presented higher tolerance to cold, due to the lower productivity reduction in this condition. IAC Milênio and IPR Andorinha, due to the greater reduction in yield under cold stress, are the most sensitive cultivars at low temperatures. The results in a controlled environment do not reflect those on the field, and it is not possible to select genotypes tolerant to cold stress the early stages of common bean development.