Genotype × environment interactions and evaluation of cotton cultivars*

Abstract

Stoneville 7A and Deltapine Smooth Leaf, bred in the Mississippi delta, were the highest yielders among a small group of medium-staple United States cultivars compared over three seasons and three sites in the Ord River valley (15° 39´S.), north-western Australia. Significant cultivar x year interactions existed for lint yield, lint percentage, boll weight, micronaire and Pressley strength, and significant cultivar x site x year interactions occurred for lint yield, lint percentage and staple length. Significant cultivar x site interactions occurred only for lint yield and Pressley strength. From the expected standard errors of cultivar means an evaluation procedure involving sampling for seed cotton yield over 3 years at each of six sites and two replications, but sampling for other agronomic and fibre quality attributes only at one site, was suggested. This procedure should result in standard errors of 5% or less of the mean values for all attributes. Consistency and stability of cultivar behaviour was assessed by simple rank methods, and Finlay and Wilkinson's joint regression method. The consistency of performance was such that a high probability of choosing the top yielders successfully would have attended early selection.

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* The field work reported in this paper was carried out by the senior author when he was a member of the Division of Land Use Research, CSIRO.