小麦纹枯病菌对三唑酮不同敏感性菌株的生物学特性及对不同杀菌剂的敏感性

Biological characteristics of Rhizoctonia cerealis isolates with different sensitivities to triadimefon and their sensitivity to different fungicides

为预测小麦纹枯病菌对三唑酮抗药性的发展趋势,采用菌丝生长速率法测定了2013年分离自河南省16个地市的98株菌株对三唑酮的敏感性,比较不同敏感性菌株的生物学性状差异,并分析了其中22株菌株对其它10种杀菌剂的敏感性。结果表明:小麦纹枯病菌群体中已出现对三唑酮敏感性下降的菌株,其中有90株菌对杀菌剂的敏感性属于正态分布,以其EC_(50)均值1.91μg/mL作为小麦纹枯病菌对三唑酮的敏感性基线。敏感菌株菌丝生长速度较快,可达8.50~12.86 mm/d,菌核产量较多,为35.80~42.90 mg/皿,生存适合度较高;敏感性下降及抗性菌株的致病性及菌核萌发等都未发生改变,但菌丝生长速率仅为5.36~10.02 mm/d,菌核产量为9.00~36.90 mg/皿,均下降明显,生存适合度降低;低抗菌株与敏感菌株在菌落形态上相同,但菌丝分枝数增多且分枝菌丝变短。三唑酮对小麦纹枯病菌的毒力较小,EC_(50)大于其它10种杀菌剂;戊唑醇、氟环唑、烯唑醇、咯菌腈和噻呋酰胺的毒力均较大,其EC_(50)≤0.10μg/mL;其余5种杀菌剂的EC_(50)在0.13~0.69μg/mL之间;小麦纹枯病菌对三唑酮的敏感性与其它10种杀菌剂间的决定系数为0.003~0.200,存在微弱的正相关性,表明在生产中这些杀菌剂可与三唑酮轮换或交替使用。

In order to forecast the resistance development of Rhizoctonia cerealis to triadimefon, the sensitivities of 98 isolates to triadimefon isolated in 2013 from 16 cities in Henan Province were determined by mycelial growth rate method; biological characteristics of the isolates with different sensitivities to triadimefon were studied, and the sensitivities of 22 isolates to ten other fungicides were also determined. The subpopulation with less sensitive to triadimefon was discovered in the tested isolates. The mean EC（50） value of 1.91 μg/mL for 90 isolates showed a unimodal curve distribution, which was treated as the sensitive baseline of R. cerealis to triadimefon. The sensitive isolates had higher survival fitness,which implied that their mycelia grew faster with 8.50-12.86 mm/d, and they could produce more sclerotia with 35.80-42.90 mg per dish. Both the mycelia growth rate（5.36-10.02 mm/d） and sclerotium dry weight（9.00-36.90 mg per dish） of slightly sensitive and resistant strains were lower, indicating that the resistant strains had lower survival fitness, though their pathogenicity and the sclerotium germination did not change. The number of hyphal tip branching of slightly resistant isolates was greater than that of sensitive isolates, but the length of the branched hypha was less than that of sensitive isolates.The EC（50） value of triadimefon to R. cerealis was greater than those of ten other fungicides, suggesting that the virulence of triadimefon was weaker. The virulence of tebuconazole, epoxiconazole, diniconazole, fludioxonil and thifluzamide was stronger, as their EC（50） values were less than or equal to 0.10 μg/mL.The EC（50） value of five other fungicides varied from 0.13 μg/mL to 0.69 μg/mL. Moreover, the determination coefficients existing between triadimefon and ten other fungicides ranged from 0.003 to 0.200,showing that there was a weak cross resistance and the ten fungicides could be used to control wheat sharp eyespot as an alternative of triadimefon.