Seleção de genótipos de algodoeiro herbáceo submetidos ao estresse hídrico e a irrigação suplementar no semiárido

Abstract

Cotton is an important Brazilian commodity, and responsible to wide number of jobs and income. In the semiarid region, cotton crop is quite dependent on rainfall irregularities and high evapotranspiration, thus, regular irrigation is necessary in order to ensure yield and quality. The use of drought tolerant cultivars is the main tolls to guarantee the production. The cotton genetic improvement have invested in combinations that add wide environmental adaptation, high yield and fiber quality. Here, we studied the productive behavior and genetic parameters of cotton top lines submitted to water stress (Chapter I) and supplementary irrigation (Chapter II) in semiarid climates (Serra Talhada-PE and Apodi-RN). Genotypes were kindly provided by Embrapa Algodão (18 top lines and two control cultivars, BRS 286 and BRS 336). A randomized blocks was adopted in all essays. The following traits were evaluated: seed cotton yield and lint cotton yield, fiber percentage, boll weight, fiber length, resistance, elongation, micronaire and Count Strength Product (CSP). Data were submitted to individual and joint analysis of variance. Further, selection of genotypes were performed adopting the Mulamba and Mock (1978) - selection index. Expressive gains of selection were found though estimative of genetic parameters. The top lines CNPA 2006-3052, CNPA 2006-1109 and CNPA 2005-128 showed tolerance to water stress and CNPA 2006-3052, CNPA 2004-266, CNPA 2006-1073 and CNPA 2005-125 showed good performance in irrigation trials. Despite the genetic value of the materials, the top line CNPA 2006-3052 showed high potential to textile industry, revealing excellent performance in both dry and irrigated conditions. Further breeding advances should be proceeded in this line focusing on tolerance to semiarid environment.