Evaluation of sowing density is an important factor for achieving maximum yields without affecting other agronomic traits. Field experiments were conducted during three consecutive years (2008, 2009 and 2010) to determinate the effect of four sowing density (62,500; 83,333; 100,000 and 142,857 pl ha−1) on yields and its components of two cotton varieties, ‘Delta Pine 16′ and ‘SN-290′ in Venezuela. The traits evaluated were lint yield, boll weight, number of seeds per boll, 100-seed weight, and fiber content. Highly significant differences (p ≤ 0.01) were observed among genotypes, sowing density and their interactions for all traits. Sowing density was not affected by year factor. High lint yield was found in ‘SN-290′ (4216.2 kg ha−1) at 100,000 pl ha−1; and in ‘Delta Pine 16′ (3917.3 kg ha−1) at 83,333 pl ha−1. The highest sowing density (142,857 pl ha−1), decrease lint yield and yield components in the genotypes. The highest boll weight was obtained by ‘SN-290′ with 6.4 g in average. All sowing densities evaluated resulted in lint percentages above 40%. Cotton lint yield was positively correlated with all yield components. Our results indicate that highest lint yields could be obtained with sowing densities between 83,333 and 100,000 pl ha−1 depending upon varieties used across savannahs of Venezuela.
There is a steady increase of demands for textile crops, where cotton is the most popular natural fiber, therefore, it is necessary to exploit cotton genetic resources. In order to develop and improve crop populations, a cotton breeding program requires access to new sources of germplasm. With the objectives to evaluate the productivity of local and introduced genotypes from Syria and Brazil, and to expand the genetic base in the Venezuelan Cotton Breeding Program, 16 genotypes were evaluated at three locations in Venezuela during 2013 and 2014 using a randomized complete block design, with three replications. The traits evaluated were plant height, stem diameter, lint yield, boll weight, number of seed per boll, 100-seed weight, and fiber content. Highly significant differences (P≤0.01) were observed among genotypes, environments and their interaction for all traits, except for lint yield and number of seed per boll across environments. ʻC-2955-25ʼ showed high yield (3514.3 kg.ha-1) but was unstable across environments used in the evaluation. ʻL-2955-13ʼ was stable across the environments, suggesting that it would be a good parent. All the genotypes obtained values of lint percent above of 38%. The Syrians genotypes ʻAleppo-11ʼ and ʻAleppo-90ʼ showed high lint yield and good agronomic performance. Genotypes identified in this study could be used as potential sources of germplasm to be introduced in future breeding programs.
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.
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