Genetic gain in lint yield and its components of upland cotton released during 1963 to 2010 in Venezuela

To respond to the high demand for cotton (Gossypium hirsutum L.) fiber, constant enhancements by breeding or management are required. The study of the genetic progress shows the changes in traits over the years, providing information about the real contribution and benefits of breeding and management efforts. In order to estimate the genetic progress of nine upland cotton cultivars for the lowlands agroecology of Venezuela released from 1963 to 2010, evaluations were performed in three locations in Venezuela during 2012 and 2013. Lint yield (LY), boll weight (BW), number of seeds per boll (SB), seed index (SI), lint content or percent (LP), plant height (PH), and stem diameter (SD) were measured. Combined analysis of variance showed differences (P <= .01) among the cultivars, environments, and their interaction for all traits, except for SB and SI. All variables have increased for the period evaluated, except for PH that showed a gradual decrease of 0.12% yr(-1). LY increased by 10.06 kg ha(-1) yr(-1) or 0.29% yr(-1), which is a total of 503 kg ha(-1) in 50 years. A reduction of PH (0.19 cm yr(-1)) was observed, meanwhile BW (0.0022 g yr(-1)), SB (0.0029 yr(-1)), SI (0.0038 g yr(-1)), SD (0.0013 cm yr(-1)), and LP (0.0071% yr(-1)) increased 0.04, 0.01, 0.04, 0.08 and 0.02% yr(-1), respectively, in the same period. These results indicate that the introduction of genotypes with divergent backgrounds and development to specific agroecologies have contributed to constant genetic progress in cotton cultivated in Venezuela.