The coexistence of generalist and specialist clonal lineages in natural populations of the Irish Famine pathogen Phytophthora infestans explains local adaptation to potato and tomato

Phytophthora infestans, causing late blight on Solanaceae, is a serious threat to potato and tomato crops worldwide. P. infestans populations sampled on either potato or tomato differ in genotypes and pathogenicity, suggesting niche exclusion in the field. We hypothesized that such niche separation can reflect differential host exploitation by different P. infestans genotypes. We thus compared genotypes and phenotypes in 21 isolates sampled on potato (n = 11) or tomato (n = 10). Typing at 12 microsatellite loci assigned potato isolates to the 13_A2, 6_A1 and 1_A1 lineages, and tomato isolates to the 23_A1, 2_A1 and unclassified multi-locus genotypes. Cross-inoculations on potato and tomato leaflets showed that all isolates were pathogenic on both hosts. However: tomato isolates performed much better on tomato than did potato isolates, which performed better on potato than did tomato isolates, thus revealing a clear pattern of local adaptation. Potato isolates were significantly fitter o...致病疫霉（Phytophthora infestans）可引发茄科植物晚疫病，是全球范围内严重威胁马铃薯与番茄作物生产的重要病原物。从马铃薯或番茄植株上分离得到的致病疫霉种群，其基因型与致病性均存在差异，这表明该病原在田间存在生态位排斥现象。我们提出假说，认为此类生态位分化可反映不同致病疫霉基因型对寄主的利用策略存在差异。为此，我们对21株分离菌株的基因型与表型进行了比较，其中11株分离自马铃薯（n = 11），10株分离自番茄（n = 10）。通过12个微卫星位点（microsatellite loci）分型，将马铃薯分离菌株归为13_A2、6_A1及1_A1谱系，番茄分离菌株则归为23_A1、2_A1谱系以及未分类的多位点基因型。以马铃薯与番茄的叶片小叶为材料开展的交叉接种试验显示，所有分离菌株均可侵染两种寄主。然而：番茄菌株在番茄寄主上的致病表现远优于马铃薯菌株，而马铃薯菌株在马铃薯寄主上的致病表现则优于番茄菌株，由此清晰呈现出明确的本地适应性模式。马铃薯菌株的适合度显著更高……