Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824.
Agricultural Research Service, U.S. Department of Agriculture, East Lansing, MI 48824.
Plant Dis. 2021 Oct;105(10):3111-3117. doi: 10.1094/PDIS-09-20-1990-RE. Epub 2021 Nov 9.
anastomosis group (AG) 2-2 can cause seedling damping-off in sugar beets and substantial losses may occur in all regions where beets are grown. Sugar beets are planted early in the season when soil temperatures are low in order to maximize the length of the growing season and minimize the risk of damping-off. However, predictive models that indicate there is little to no risk of Rhizoctonia damping-off at temperatures <15°C may not be entirely reliable. We tested this possibility by inoculating sugar beet seedlings in a growth chamber at 11°C with 35 AG 2-2 isolates that were representative of the genetic diversity present in AG 2-2. Although disease progress and growth rate were greatly reduced at 11°C, considerable disease symptoms did develop in inoculated plants. Three weeks after inoculation, 16% of the plants were dead and 77% of the isolates tested had average disease severity scores that were significantly greater than those of the mock inoculated control. This confirms our concern about the possibility for low-temperature infection of sugar beets and indicates that waiting until the soil warms up to above 15°C to apply fungicide could leave the crop at risk. Aggressiveness does not appear to be related to subgroup or growth rate but rather depends on the response of the specific isolate to low temperature.
在所有种植甜菜的地区，2-2 融合群（AG）都可能导致甜菜幼苗猝倒病，造成重大损失。为了最大限度地延长生长季节并降低猝倒病的风险，甜菜通常在季节早期种植，此时土壤温度较低。然而，指示在温度 <15°C 下根腐病风险很小或不存在的预测模型可能并不完全可靠。我们通过在 11°C 的生长室中用 35 个代表 AG 2-2 遗传多样性的 AG 2-2 分离物接种甜菜幼苗来检验这种可能性。尽管在 11°C 时，病情进展和生长速度大大降低，但接种植物确实出现了相当严重的症状。接种后 3 周，16%的植株死亡，测试的 77%的分离物的平均病情严重程度显著高于模拟接种对照。这证实了我们对甜菜低温感染可能性的担忧，并表明等到土壤温度升高到 15°C 以上再施用药剂可能会使作物面临风险。侵袭力似乎与亚群或生长速度无关，而取决于特定分离物对低温的反应。
