Performance of wheat cultivars and cultivar mixtures in the presence of Cephalosporium stripe

Wheat cultivars and cultivar mixtures were grown in commercial fields naturally infested with Cephalosporium gramanium. Thirteen treatments, including nine cultivars and four two-way cultivar mixtures, were replicated four times in 3 x 30 in plots in each of six experiments (two locations x three winter wheat seasons). Cephalosporium stripe was quantified by estimating the percentage of prematurely ripening heads (whiteheads) in each plot. There was little variation in percentage of whiteheads among club wheat entries, which were less susceptible than the common soft white winter wheats. Common wheat entries varied from highly susceptible to moderately resistant. One cultivar mixture significantly (P < 0.01) increased the percentage of whiteheads as compared to the mean of its component cultivars grown in pure stand in four of the six experiments; mixtures never significantly decreased the percentage of whiteheads. All four cultivar mixtures significantly reduced lodging in the one experiment where there was sufficient eyespot (caused by Pseudocercosporella herpotrichoides) to cause lodging. Averaged over the six experiments, the four cultivar mixtures yielded 7.5, 6.9, 3.4, and -1.7% more than the means of their component cultivars grown in pure stand; the highest yielding club wheat and the highest yielding common wheat treatment were both cultivar mixtures. Cultivars varied in parameters of yield stability, with no obvious difference between susceptible and resistant cultivars. Cultivar mixtures demonstrated greater yield stability than did the individual cultivars. (C) 2002 Elsevier Science Ltd. All rights reserved.