Heterosis and combining ability effects on cotton. II. Heterosis

Abstract

The yield and quality of a diverse range of cotton hybrids was measured in one, or more, of a number of experiments conducted in the Ord River valley, Western Australia (15¦S.) and the Namoi River valley, New South Wales (30¦S.). Two of the experiments were diallels, one involving nine parents, the other thirteen parents. In both the plant and subsequent ratoon crops, mean yield of the hybrids was significantly greater than the mean yield of the parents, and the hybrids had significantly longer and stronger fibre. A few hybrids in both diallels significantly outyielded commercial controls by between 15 and 35% in both the plant and ratoon crops. Subsequently, in other experiments including one with near-commercial large plots, the high performers from the diallel experiments were inconsistent for yield, usually exhibiting little or no heterosis above that of the best commercial cultivars. Other hybrids tested in these experiments also generally failed to outyield the commercial controls, although a number had higher-quality fibre. It was concluded the heterosis for yield is not consistent enough under high-yielding Australian conditions to warrant the commercial production of hybrid cotton seed. Some hybrids, however, especially the interspecific G. hirsutum x G. barbadense ones, have the stronger, finer fibre that appears better suited to cotton spinning equipment now being developed, and this aspect could justify reappraisal of this conclusion in the future.