稻田土壤中稻曲病菌厚垣孢子的越冬能力研究

Overwintering survival of Villosiclava virens chlamydospores in rice field soils

稻曲病菌(Villosiclava virens)可侵染水稻引发稻曲病,目前对于V.virens是以菌核还是厚垣孢子越冬存在争议。2021和2022年,浙江省杭州市萧山区的一处稻田均发生了较严重的稻曲病。本研究于2021年10月-2022年11月对该稻田中V.virens的菌核和厚垣孢子进行持续监测,并检测了厚垣孢子的萌发能力,以明确V.virens的越冬方式。结果显示,5次采集的稻田土样(每次在田埂和田内分别随机选取9个采样点),除2022年1月和5月从田埂采样点采集的土壤样品中未镜检观察到厚垣孢子外,其余都至少有1个采样点的土样可镜检到厚垣孢子。进一步利用巢式PCR进行分子检测,所有田内和田埂采样点中,都至少有1个采样点的土样可检测到V.virens。23℃和4℃条件下稻曲球厚垣孢子的存活期分别约为7和13个月。4℃条件下保存6个月后,土样中的厚垣孢子仍有萌发能力。2021年10月-2022年10月经田间调查以及对采集的土样进行镜检,均未发现菌核,仅于2022年11月9日从稻曲球上检查到菌核,菌核携带率仅为3.14%。因此,判断本研究采样的稻田2021年V.virens以厚垣孢子形式在土壤中越冬,并作为主要初侵染源引发次年的稻曲病。

Villosiclava virens can infect rice plants and cause rice false smut.At present,it is still controversial whether V.virens overwinters in the form of sclerotia or chlamydospores.In both 2021 and 2022,rice false smut was obviously observed in the rice fields in Xiaoshan District,Hangzhou City,Zhejiang Province.To clarify the overwintering form of V.virens in these fields,the survival of sclerotia and chlamydospores was continuously monitored from October 2021 to November 2022.The results showed that among all soil samples collected for 5 times(9 randomly selected sites in both rice-planting fields and ridges for each time),chlamydospores could be observed by microscope in at least 1 site for each sampling time except for ridge sites for 2 sampling times(January and May of 2022);V.virens could be detected by nested PCR in at least 1 sampling site from both riceplanting fields and field ridges;the survival periods of chlamydospores preserved at 23℃and 4℃C were about 7 and 13 months,respectively;chlamydospores in soil samples still had the ability to germinate after storage for 6 months at 4℃.From October 2021 to October 2022,no sclerotium was found in our sampling fields and collected soil samples.Only a few sclerotia were found on rice false smut balls on November 9th,2022.However,the sclerotium-bearing rate of rice false smut balls was only 3.14%.Taken together,it was concluded that V.virens overwintered by the form of chlamydospores in soils of the sampling rice fields in 2021,which became the main primary infection source in 2022 and caused rice false smut.