Comportamento de genótipos de algodoeiro submetidos a estresse salino

Abstract

Salinity is an abiotic stress of global occurrence that damages agricultural production, leading to economic losses. Osmotic and salt absorption specific ion effects cause funcional disturbances on plants, limiting photosynthesis due to stomata closure and damage to chloroplasts. Beyond that, excess salts causes inhibition of germinative potential, reduction of primary and lateral roots growing and decrease in productivity. However, plants respond differently to salinity stress, depending on the species, genotype, phenological stage and duration of salt exposure. This paper has the objective of identify cotton plants’ genotypes that tolerate salinity stress through agronomic and physiological descriptors. Nine cotton plants’genotypes had been cultivated in a vegetation house (G1-BRS Seridó, G2-BRS 286, G3- FM 966, G4-CNPA 7MH, G5-FMT 701, G6-CNPA 5M, G7-CNPA ITA 90, G8-FMT 705 and G9- BRS Rubi) submitted, for 35 days, to irrigation of saline water (CEw de 6,0 dSm^-1). The experimental delimitation was casual blocks, constituted by a factorial arrangement 9 x 2, with four repetitions, totalizing 72 parcels. This work evaluates growth, gas exchange and fluorescence of chlorophyll a. Multivariate Analysis with non-hierarchical (main components) and hierarchical (UPGMA) methods treated data. Salinity caused significant reductions on variables of gas exchange and fluorescence. BRS Seridó, CNPA 7MH, CNPA 5M, CNPA ITA 90, FMT 705 and BRS RUBI farm’s beat osmotic stress imposed by saline environment, by diferente means, showing increase or conservation of photosynthetic rate (A). Between those genotypes, BRS Seridó, CNPA ITA 90, FMT 705 and BRS Rubi stand out. They are most promissing for showing conservation or increase of A with conservation or reduction of gs and E. Experiment execution provided valuable informations for better understanding effects of salinity in this species. Selected farms are important for cotton improvement program, aiming on getting superior lineages tolerant to saline stress.