Temporal dynamics of plant competition in genetically diverse wheat populations in the presence and absence of stripe rust.
Effects of disease and environment on competitive interactions among wheat genotypes were investigated. Wheat genotypes (5) were grown in up to 6 different 2-way combinations and as pure stands in 2 or 3 locations during 1 to 3 growing seasons in the presence and absence of wheat stripe rust (caused by Puccinia striiformis). Overall yield of the mixtures relative to the means of the monocultures did not differ among locations and years. However, interactions between genotypes were often affected by location and to a lesser degree by year. Disease significantly affected seed weight and seed number of the 2 susceptible genotypes in pure stands and in mixtures. Disease also led to changes in competitive interactions between resistant and susceptible genotypes. Competitive interactions among genotypes often changed from early in the season (as measured by the number of tillers) to late in the season (as measured by yield/tiller). In a few mixtures negative correlations between early competitive ability (relative number of tillers) and components of late competition suggested that intra-genotypic competition might have been stronger than inter-genotypic competition.