Phytopathology. 2002 Jun;92(6):624-30. doi: 10.1094/PHYTO.2002.92.6.624.
ABSTRACT The selective effect of quantitative host resistance on pathogen aggressiveness is poorly understood. Because two previous experiments with a small number of bread wheat cultivars and isolates of Mycosphaerella graminicola had indicated that more susceptible hosts selected for more aggressive isolates, we conducted a larger experiment to test that hypothesis. In each of 2 years, six cultivars differing in their levels of partial resistance were planted in field plots, and isolates were collected from each cultivar early and late in the growing season. The isolates were inoculated as populations bulked by cultivar of origin, field replicate, and collection date on seedlings of the same six cultivars in the greenhouse. The selective impact of a cultivar on aggressiveness was measured as the difference in aggressiveness between early and late isolates from that cultivar. Regression of those differences on disease severity in the field yielded significance values of 0.0531 and 0.0037 for the 2 years, with moderately resistant cultivars selecting for more aggressive isolates. In a related experiment, the protectant fungicide chlorothalonil was applied to plots of two susceptible cultivars to retard epidemic development. When tested in the greenhouse, isolates of M. graminicola from those plots were significantly more aggressive than isolates from the same cultivars unprotected by fungicide.
摘要 定量的寄主抗性对病原菌侵袭力的选择作用还不太清楚。因为以前有两个用少量小麦品种和禾谷球腔菌分离物进行的试验表明，较感病的寄主选择了侵袭力较强的分离物，所以我们进行了一个较大的试验来检验这个假说。在两年的每一年中，将 6 个在部分抗性水平上不同的品种种植在田间小区，然后从每个品种的早期和晚期分别采集分离物。将这些分离物按品种来源、田间重复和采集日期混合成群体，接种在温室中同样的 6 个品种的幼苗上。用一个品种的早期和晚期分离物之间侵袭力的差异来衡量该品种对侵袭力的选择影响。这两年的回归分析得出的显著值分别为 0.0531 和 0.0037，表明中度抗性品种选择了侵袭力更强的分离物。在一个相关的试验中，保护性杀菌剂百菌清被施用于两个感病品种的小区以延缓病害的发展。当在温室中进行测试时，来自这些小区的禾谷球腔菌分离物比未用杀菌剂保护的同一品种的分离物侵袭力明显更强。
