Tolerância de genótipos de algodoeiros naturalmente coloridos ao estresse salino cumulativo.

Abstract

Scarcity of good quality water is a limiting factor for irrigated agriculture, especially in arid and semi-arid regions. In such circumstances, the use of water with high salt content is an alternative to be considered for crop irrigation. In this context, it is necessary to identify the genotypes that have economic potential and are tolerant to salt stress, and the appropriate saline water irrigation strategies, aiming to ensure the sustainability of the production system. In this work, we aimed to evaluate the tolerance of colored cotton genotypes to cumulative salt stress at different plant development stages, as well as the influence of salinity in which the seeds were formed, on the growth and production of individuals originated from them in a new crop cycle. Two experiments were conducted in a greenhouse at UFCG, Campina Grande - PB, evaluating three naturally colored cotton genotypes (G1 - BRS Rubi; G2 - BRS Topázio and G3 - BRS Safira). In the first experiment, seven salinity management strategies were studied by varying the quality of the water applied at different stages of the plant cycle. The second experiment evaluated the effects of high salinity water usage alternated with water with a low concentration of salts on the production of plants grown from seeds collected in the first experiment, subjected to ten salinity management strategies, also varying the phenological stage of the cotton plants. The first experiment consisted of a 3 x 7 factorial design with three plants per plot and three replications, and the second experiment had a 3 x 10 factorial with three replications, two plants per plot; both were in randomized blocks. Physiological and production growth variables of the plants were evaluated. Data were subjected to the 'F' test (p <0.05) and to the Scott-Knott cluster averages analysis (p <0.05) for the strategy factor of irrigation management, and Tukey test (p <0.05) between cotton genotypes. Plants of the genotypes studied in cotton can be irrigated with saline water (9 dS m-1) in the vegetative phase in the first cycle, but in a new cycle, plants originating from seeds produced under saline conditions can not be irrigated with Water in the vegetative phase. The plants that were most sensitive to salinity in the fruiting phase, in the first experiment, in the second cycle, the seeds harvested from these plants gave individuals more tolerant to salt stress, recovering all indexes of the physiological parameters. The plants acclimated to salinity, because when they originated from seeds formed under salt stress, even when irrigated with high salinity in the flowering and fruiting phases, they maintained high levels of cocoa production and fiber quality. Acclimatization was also reflected in high indexes of physiological parameters. The oil content of the cotton genotype seeds was not affected by cumulative saline stress in plants derived from seeds formed with salinized water in the previous cycle.