甘薯长喙壳菌对咯菌腈的敏感基线及咯菌腈对甘薯黑斑病的防治效果

Sensitivity baseline of Ceratocystis fimbriata to fludioxonil and control efficacy of fludioxonil against black rot of sweet potato

为探索甘薯长喙壳菌Ceratocystis fimbriata对咯菌腈的敏感性,明确咯菌腈在苗期和储藏期对甘薯黑斑病的防治效果,分别从中国河南、四川、河北、山东采集并分离得到64株甘薯长喙壳菌;采用凹玻片法观察了咯菌腈对病原菌分生孢子萌发和芽管伸长的影响;采用孢子萌发法和菌丝生长速率法测定了64个菌株对咯菌腈的敏感性,并对50%咯菌腈可湿性粉剂(WP)防治苗期和储藏期甘薯黑斑病的效果进行了评价。结果表明:随咯菌腈处理浓度增加,甘薯长喙壳菌分生孢子的萌发率逐渐下降,芽管扭曲程度逐渐加大。咯菌腈还可造成菌株芽管过早出现分支。咯菌腈对供试菌株分生孢子萌发的EC_(50)值在0.20~0.99μg/mL,平均值为0.52μg/mL;对菌丝生长的EC_(50)值在0.17~0.31μg/mL,平均值为0.24μg/mL,不同敏感性菌株所占频率呈正态分布,可作为甘薯长喙壳菌对咯菌腈的敏感基线。50%咯菌腈WP在有效成分500 mg/L下浸苗处理,对薯苗黑斑病的防治效果可达90.24%,显著高于500 g/L甲基硫菌灵悬浮剂(SC)同浓度下的处理。采用浸薯块法防治储藏期黑斑病,50%咯菌腈WP 500 mg/L连续两年的防治效果分别达到84.41%和82.30%,也显著高于同浓度的甲基硫菌灵。药剂处理后60和90 d,甘薯块中咯菌腈的残留量低于其最大残留限量(MRL)标准。本研究表明,咯菌腈具有防治甘薯生长期和储藏期黑斑病的潜力。

The objective of this study is to investigate the sensitivity of Ceratocystis fimbriata to fludioxonil,and evaluate the control efficacy of fludioxonil against the black rot of sweet potatoes during the seedling and storage stages.A total of 64 isolates were collected from sweet potatoes in Henan,Sichuan,Hebei,and Shandong Provinces.With the concave slide tests,the effect of fludioxonil on spore germination and germ tube elongation was observed.The sensitivity of 64 isolates was determined by spore germination and mycelial growth rate methods respectively.Meanwhile,the control efficacies of fludioxonil 50%WP against the black rot of sweet potatoes in the seedling and storage stages were evaluated.The results showed that the conidia germination rate of C.fimbriata decreased gradually and the tortuosity of the germ tube increased gradually with the increase of fludioxonil concentrations.Fludioxonil could also cause premature branching of the germ tube.EC_(50) values of fludioxonil against spore germination ranged from 0.20μg/mL to 0.99μg/mL,with a mean of 0.52μg/mL.EC_(50) values of fludioxonil against mycelial growth ranged from 0.17μg/mL to 0.31μg/mL,with a mean of 0.24μg/mL.As the sensitivity frequency showed normal distribution,the mean EC_(50) values could be regarded as the baseline sensitivity of C.fimbriata to fludioxonil.The control efficacy of fludioxonil 50%WP on seedlings of sweet potato dipped in the suspension of 500 mg a.i./L fludioxonil was 90.24%,which was significantly higher than that of thiophanate-methyl 500 g/L SC at the same concentration during the seedling stage.The control efficacies of fludioxonil dipped in the suspension of fludioxonil at 500 mg a.i./L for two consecutive years were 84.41%and 82.30%,respectively,which were also significantly higher than that of thiophanate-methyl dripped in the suspension of thiophanate-methyl with the same concentration during storage process.The residues of fludioxonil were lower than the maximum residue limit(MRL)at 60 d and 90 d after application.This study suggested fludioxonil has great potential to control the black rot of sweet potatoes during both growth and storage stages.