Identification, Biological characteristics, and Fungicides screening of the Pathogen causing Leaf spot disease on Pittosporum tobira
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摘要:
目的 明确引起重庆市万州区海桐叶斑病的病原及其生物学特性,并筛选出有效防治药剂。 方法 采用组织分离法从具有典型症状的海桐叶片分离病原菌,进行致病性测定,采用形态学和分子生物学方法对病原菌进行鉴定,用菌丝生长速率法进行病原菌生物学特性和室内药剂筛选。 结果 从病叶中分离获得菌株HT10,将其回接于健康叶片上,接种后病斑中央呈灰褐色,边缘棕褐色,外围有黄色晕圈,与田间症状一致,符合柯赫氏法则的致病性测定;PDA培养基上菌丝呈棕黑色,分生孢子倒棒状、卵形或近椭圆形,表面具横隔和纵隔;经多基因(ITS、GAPDH和RPB2)系统发育分析,其与长柄链格孢(Alternaria longipes)聚集在同一分支;A. longipes最适生长条件为:PDA培养基,全光照,28 ℃和pH 6.0,碳源和氮源分别是蔗糖和甘氨酸,致死温度41 ℃ / 15 min。室内毒力测定结果表明,25%抑霉·咯菌腈悬乳剂抑菌作用最强,EC50为0.799 μg·mL−1,400 g·L−1克菌·戊唑醇悬乳剂抑菌作用最弱,EC50为370.457 μg·mL−1。 结论 海桐叶斑病的致病菌为长柄链格孢(A. longipes),这是A. longipes侵染海桐引起叶斑病的首次报道;25%抑霉·咯菌腈悬乳剂对A. longipes有较强的抑制作用。 Abstract:Objective The present paper aimed to identify the pathogen causing leaf spot on Pittosporum tobira, to study the biological characteristics of the pathogen, and screen out effective fungicides to control this disease. Method The pathogen was isolated from the leaves with typical symptoms by tissue separation method and verified by pathogenic test. The morphological and molecular biology methods were used to identify species of the pathogen. The mycelium growth in plate was used to investigate the biological characteristics and fungicides toxicity of the pathogen. Result The HT10 strain was isolated from the disease leaves and inoculated onto healthy P. tobira. After inoculation, the center of the disease spot was grayish brown, the edge was brown, and the periphery was yellow halo, which was consistent with the field’s symptoms. On PDA media, the fungal colonies displayed brown and black. Conidia were inverted rod, ovoid or nearly elliptic, with transverse and longitudinal septa. The phylogenetic analysis used multiple genes of ITS, GAPDH and RPB2 clustered the isolate with Alternaria longipes clade. The optimum growth condition on PDA were full light, 28 ℃ temperature and, 6.0 pH. The optimal carbon source or nitrogen source is sucrose or glycine, respectively. The lethal temperature is 41 ℃/15 min. Laboratory toxicity test showed that the 25% SC of Imazalil·Fludioxonil has the best inhibitory effect to pathogenic fungus with EC50 of 0.799 μg·mL−1 and the 400 g·L−1 SC of Captan·Tebuconazole has the worst inhibitory effect with EC50 of 370.457 μg·mL−1. Conclusion The pathogen causing the leaf spot disease on P. tobira is A. longipes, which is the first report of leaf spot disease on P. tobira caused by A.longipes. 25% SC Imazalil·Fludioxonil has a strong inhibitory effect on the growth of A. longipes. -
图 3 基于ITS、GAPDH和RPB2序列构建的多基因系统发育树
分支上的数值为 1000 次重复后的 Bootstrap;B. oryzae(CBS 157.50)为外类群;HT10为本研究分离的菌株。
Figure 3. Multi-loci phylogenetic analysis based on ITS, GAPDH, and RPB2 sequences
The value on the branch is the bootstrap value after 1000 repetitions; B. Oryzae (CBS 157.50) is an outgroup; HT10 is the strain isolated in this study.
表 1 杀菌剂对长柄链格孢菌丝生长的抑制效果
Table 1. Inhibition effect of fungicides on mycelium growth of Alternaria longipes
杀菌剂
Fungicide毒力回归方程
Virulent regression equation相关系数R2
Correlation coefficient抑制中浓度
EC50/(μg·mL−1)25%抑霉·咯菌晴悬乳剂
Imazalil·Fludioxonil 25% SC (Suspension Concentrate, SC)y = 0.2647x + 5.0583 0.9900 0.799 25%多菌灵可湿性粉剂
Carbendazim 25% WP (Wettable Powder, WP)y = 0.2761x + 3.8609 0.9964 61.908 45%咪鲜胺微乳剂
Prochloraz 45% ME (Micro Emulsion, ME)y = 0.3644x + 4.7093 0.9918 2.214 30%吡唑醚菌酯乳油
Pyraclostrobine 30% EC (Emulsifiable Concentrate, EC)y = 0.7618x + 0.8093 0.9783 246.434 400 g·L−1克菌·戊唑醇悬浮剂
Captan·Tebuconazole 400 g·L−1 SC (Suspension Concentrate, SC)y = 0.931x − 0.4898 0.9708 370.457 -
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