a1 Plant Breeding Institute, Tumkpington, Cambridge
The graphical and statistical analyses of competition diallels devised by Durrant were applied to an experiment investigating competition between four spring-wheat varieties. The results indicated that at low seed rates mixtures between varieties having a wide phenotypic difference between them in competitive characters, such as height and early maturity, could significantly outyield pure-stands of the component varieties. However, the results of a second experiment, in which these mixtures were grown at a range of seed rates, indicated that the yield advantage of mixtures over pure-stands was unlikely to occur at normal seed rates.
It is suggested that, at the low seed rates likely to be used in growing F1 hybrid wheat crops, mixtures of F1 hybrids and male parental lines might achieve very nearly the same yield as the pure F1 hybrid variety with a seed bulk that was cheaper to produce.
(Received July 29 1971)