Pasche J S, Taylor R J, Gudmestad N C
Department of Plant Pathology, North Dakota State University, Fargo 58102.
Plant Dis. 2010 Jul;94(7):905-914. doi: 10.1094/PDIS-94-7-0905.
Colonization of potato (Solanum tuberosum) tissue, including roots, stolons, and above and below ground stems, by Colletotrichum coccodes, the causal agent of black dot, was evaluated following soil infestation, inoculation of seed tubers and foliage, and every combination thereof, in field trials over two growing seasons in North Dakota and Minnesota. A total of 107,520 isolations for C. coccodes performed across four site-years allowed for an extensive comparison of fungal colonization of the host plant and disease severity. The black dot pathogen was detected in potato stems at the first sampling date in all four site-years, as early as 14 days prior to emergence. Colonization of above and below ground stems occurred at a higher frequency than in roots and stolons in all four site-years, resulting in significantly higher relative area under the colonization progress curves (RAUCPCs) (α = 0.05). Although fungal colonization and disease incidence were higher in inoculated and/or infested treatments, sufficient natural inoculum was present to result in substantial levels of disease in noninoculated and noninfested plots. However, noninoculated and noninfested plots displayed the lowest RAUCPC values across three of four site-years and those treatments with multiple inoculation events tended to have higher RAUCPC values. Isolates belonging to vegetative compatibility group (VCG)2 and -5 were recovered from plants sampled in 2004 more frequently than isolates belonging to VCG1 and -3. A significant difference in disease incidence on stems was observed only in North Dakota in 2004 and Minnesota in 2003 (α = 0.05). Noninoculated and noninfested plots displayed the lowest disease incidence, whereas those treatments with more than one inoculation and/or infestation event tended to have higher disease incidence. Results of this study, including the disease severity and yield data, provide a better understanding of colonization of potato plants by C. coccodes and its impact.
在北达科他州和明尼苏达州进行的两个生长季节的田间试验中，研究了黑点病病原菌（Colletotrichum coccodes）对马铃薯（Solanum tuberosum）组织（包括根、匍匐茎以及地上和地下茎）的定殖情况，试验包括土壤侵染、种薯接种、叶片接种以及它们的各种组合。在四个地点年份共进行了107,520次对C. coccodes的分离，以便对寄主植物的真菌定殖和病害严重程度进行广泛比较。在所有四个地点年份的第一次采样日期，即在出苗前14天，就在马铃薯茎中检测到了黑点病病原菌。在所有四个地点年份中，地上和地下茎的定殖频率均高于根和匍匐茎，导致定殖进展曲线下的相对面积（RAUCPCs）显著更高（α = 0.05）。尽管接种和/或侵染处理中的真菌定殖和发病率更高，但在未接种和未侵染的地块中也存在足够的自然接种体，导致病害达到相当程度。然而，在四个地点年份中的三个年份，未接种和未侵染的地块显示出最低的RAUCPC值，而那些有多次接种事件的处理往往具有更高的RAUCPC值。从2004年采样的植物中回收的属于营养体亲和群（VCG）2和 -5的分离株比属于VCG1和 -3的分离株更频繁。仅在2004年的北达科他州和2003年的明尼苏达州观察到茎上发病率的显著差异（α = 0.05）。未接种和未侵染的地块发病率最低，而那些有不止一次接种和/或侵染事件的处理往往发病率更高。本研究的结果，包括病害严重程度和产量数据，有助于更好地了解C. coccodes对马铃薯植株的定殖及其影响。
