SUMMARYIn a 5-year study (2004–2008), the possibility of exploiting intra-cultivar variation in cotton (Gossypium hirsutum L.) was investigated. Honeycomb single-plant selection for seedcotton yield was employed within three cultivars at a low density of 1·15 plants/m2. First- and second-generation progeny lines (1GPLs and 2GPLs) were evaluated for seedcotton yield at low density at three sites, whereas third-generation progeny lines (3GPLs) were tested at the crop density of 10 plants/m2 across two sites and 2 years. Significant differentiation for seedcotton yield was discovered within cultivar (cvar) Christina and cvar Corona at both low and crop densities, and within cvar Flora at low density. In addition, significant intra-cultivar heterogeneity for fibre quality properties was found at crop density. The 1GPLs and 2GPLs grown at low density showed increases in seedcotton yield of 16 and 19%, respectively, in cvar Christina, and of 2·6 and 3·7%, respectively, in cvar Corona. In cvar Flora, the 1GPLs and 2GPLs yielded 10 and 3·3% lower than the mother cultivar, respectively. When grown at standard crop density, across sites and years, 12 and 5·2% higher yield was obtained by the Christina-derived 3GPLs and the Corona-derived 3GPLs, respectively, when compared with the original cultivars. These results provide evidence that elite cultivars are not homogeneous but rather heterogeneous material, within which selections can be made to maintain or improve uniformity and further improve desirable agronomic traits.
SINGLE-PLANT SELECTION AT ULTRA-LOW DENSITY OF FIRST GENERATION LINES OF THREE BEAN CULTIVARS UNDER WATER STRESS