Song Jiehui, Han Chenxi, Zhang Sijie, Wang Yan, Liang You, Dai Qigen, Huo Zhongyang, Xu Ke
Jiangsu Key Laboratory of Crop Genetics and Physiology & Co-Innovation Center for Modern Production Technology of Grain Crops, Agricultural College, Yangzhou University, Yangzhou 225009, China.
J Fungi (Basel). 2022 Sep 26;8(10):1008. doi: 10.3390/jof8101008.
Rice blast caused by Magnaporthe oryzae is one of the most destructive fungal diseases of rice worldwide. Stimulatory effects of low doses of fungicides on pathogens are closely relevant to disease management. In the present study, in potato dextrose agar (PDA) amended with carbendazim at a dose range from 0.003 to 0.3 μg/mL, stimulatory effects on the mycelial growth of three isolates sensitive to carbendazim were tested. Carbendazim at concentrations from 0.003 to 0.1 µg/mL showed stimulatory effects on mycelial growth of isolates Guy11 and H08-1a, while carbendazim at concentrations from 0.003 to 0.03 µg/mL stimulated the growth of isolate P131. The maximum stimulation magnitudes were 11.84% for the three isolates tested. Mycelial colonies grown on PDA amended with different concentrations of carbendazim were incubated at 28 °C in darkness for 7 days as the pretreatment. Pretreatment mycelia were inoculated on fresh fungicide-free PDA and subsequent mycelia growth stimulations were still observed, and the maximum stimulation magnitudes were 9.15% for the three isolates tested. Pretreatment mycelia did not significantly change the tolerance to H2O2 and NaCl, except that the tolerance to H2O2 was increased significantly (p < 0.05) when the carbendazim was at 0.3 µg/mL. After five generations of mycelial transference on fungicide-free PDA, the transgenerational hormesis of mycelial were exhibited when transferred onto PDA supplemented with carbendazim at 0.3 µg/mL, and the maximum percent stimulation was 51.28%. The time course of infection indicated that the visible initial necrotic symptoms could be detected at 2 DPI on leaves treated with carbendazim at 0.03 µg/mL, whereas no necrotic symptom could be discerned for the control. Statistical results of lesion area and lesion type at 7 DPI showed that there was a significant stimulation (p < 0.05) on aggressiveness of M. oryzae isolate Guy11 on detached rice leaves at 0.03 µg/mL carbendazim. These results will advance our understanding of hormetic effects of fungicides and provide valuable information for judicious application of fungicides.
由稻瘟病菌引起的稻瘟病是全球最具破坏性的水稻真菌病害之一。低剂量杀菌剂对病原体的刺激作用与病害管理密切相关。在本研究中，在添加了浓度范围为0.003至0.3μg/mL多菌灵的马铃薯葡萄糖琼脂（PDA）中，测试了多菌灵对三种对其敏感的分离株菌丝生长的刺激作用。浓度为0.003至0.1μg/mL的多菌灵对分离株Guy11和H08 - 1a的菌丝生长有刺激作用，而浓度为0.003至0.03μg/mL的多菌灵刺激了分离株P131的生长。测试的三种分离株的最大刺激幅度为11.84%。将在添加不同浓度多菌灵的PDA上生长的菌丝菌落于28℃黑暗中培养7天作为预处理。将预处理后的菌丝接种到新鲜的无杀菌剂PDA上，仍观察到后续的菌丝生长刺激，测试的三种分离株的最大刺激幅度为9.15%。预处理后的菌丝对过氧化氢和氯化钠的耐受性没有显著变化，不过当多菌灵浓度为0.3μg/mL时，对过氧化氢的耐受性显著增加（p < 0.05）。在无杀菌剂的PDA上进行五代菌丝转接后，当转移到添加0.3μg/mL多菌灵的PDA上时，菌丝表现出跨代兴奋效应，最大刺激百分比为51.28%。感染时间进程表明，在接种0.03μg/mL多菌灵处理的叶片上，在接种后2天可检测到可见的初始坏死症状，而对照未观察到坏死症状。接种后7天病斑面积和病斑类型的统计结果表明，0.03μg/mL多菌灵对离体水稻叶片上稻瘟病菌分离株Guy11的致病力有显著刺激作用（p < 0.05）。这些结果将增进我们对杀菌剂兴奋效应的理解，并为明智使用杀菌剂提供有价值的信息。
