Effects of intergenotypic competition on selection within chrysanthemum progenies

Summary Intergenotypic competition affected the growth and onset of flowering of target plants of four chrysanthemum cultivars planted within plots of the same four cultivars at commercial spacing. The relative competitive abilities of two of these cultivars, Pollyanne and Hurricane, strong and weak respectively, were confirmed when they were further grown in balanced, equal-proportion mixtures. Notwithstanding their different competitive abilities, these two cultivars had similar flower yields in pure stands and, for this character at least, would be judged to have equal commercial worth.In a further series of experiments, target plants of the female parent were grown in pre-determined positions within clonally replicated progeny plots and in equivalent positions in pure stands of the female parent. These two types of plot gave similar proportions of total target plant variance due to position, suggesting that individual plants within a segregating progeny are subjected to similar levels of competition. It is inferred that the level of competition approximates to the overall mean competitive ability of the full-sibs comprising the progeny. Selection procedures are discussed in the light of this conclusion.