Implications of correlations and genotype by environment interactions among cotton traits

Abstract

The existence of negative correlations, coupled with significant genotype x environment interaction (GE) among cotton traits poses both opportunities and challenges in breeding. This study aimed at determining the existence of GE on seed cotton (Gossypium hirsutum L.) yield, lint yield, earliness index, gin out turn ratio, 100 seed weight, split boll weight and fuzz grade and correlations, among these traits, as well as understanding the implications on variety evaluation and release. Ten genotypes from Cotton Research Institute, Zimbabwe, were evaluated across seven locations, during the 2012/13 and 2013/14 cropping years with three replications at each location. Seed cotton and lint yield, earliness index, gin out turn ratio, 100-seed weight, split boll weight and fuzz grade were measured on the genotypes at all locations. Analysis of variance for GE showed significant differences (P<0.05) on most traits, except earliness index. There were huge GE and error variance components on seed cotton yield and allied traits that reduced heritability and correlation among these traits. Seed cotton and lint yield were significantly correlated (P<0.001; r = 0.95) to each other; while split boll weight had significant correlation (P<0.004; r = 0.82) with 100-seed weight. The genotype plus GE biplot analysis showed that SZ 9523 had high and stable yield and desirable fuzz grade, which made it an ideal genotype for release. All locations belonged to one complex mega-environment with Chisumbanje Research Station more representative and most discriminating location which can be used in early generation testing of cotton.

Key Words:  Gossypium hirsutum, lint, mega-environments