Seleção de genótipos de algodoeiro herbáceo tolerantes ao estresse hídrico para produtividade e qualidade de fibra

Abstract

Cotton is one of the world's most important fiber crops grown in more than 60 countries and is responsible for the livelihoods of millions of people around the world, generating employment and income for small and large producers. In Brazil is produced in several regions in different production systems, with production estimated at 1.5 million tons, in which the States of Mato Grosso, Bahia, Goiás, Mato Grosso do Sul and Minas Gerais are the biggest domestic producers. The objective of this work was to select cotton cultivars tolerant to water stress, based on productivity and fiber quality studies.The experiment was conducted under field conditions, without water supplementation, in a semi - arid environment, in the experimental field of the CENTEC - Technological Institute of the Education Center - Quixeramobim - CE. The planting was carried out on April 24, 2018, germination began on April 30 and flowering on June 18, 2018. Nine cultivars made available by the Embrapa Germplasm Active Bank, previously selected due to fiber quality characteristics and water stress tolerance, were used. The delineation used was in blocks at random with 4 replications, the experimental unit consisted of two rows of 5 m, with manual planting, in 0.90 m spacing between rows with 7 plants per linear meter with net area of 9.0 m2 with 70 plants/plot. The characteristics of cotton seed production, fiber percentage and cotton fiber production, length, resistance, elongation, fiber uniformity, short fiber index, micronaire index and reliability index were evaluated. The data were submitted to the analysis of individual variance and the selection of the genotypes was performed through the selection index proposed by Mulamba and Mock (1978) and by the direct and indirect selection index, through the GENES software. It was verified that there is genetic variability for most of the cultivars tested, indicating that there is possibility of selection gains in breeding programs. Genetic variability was identified for the characteristics of the evaluated fibers, with the exception of the UNF and the SFI, which offers conditions to form new populations with more genetic gains. There is the possibility of genetic gain in the selection process for most of the production characters and quality of the cotton fiber in semiarid conditions. The most promising genotypes are CNPA 2013-2064 RF FL, 944 FM GL, CNPA 2012-120 RF, for presenting satisfactory results for production under rainfed conditions, these being suitable for use in breeding programs aimed at the cultivation of the semiarid region of Brazil.