为筛选能有效抑制烟草叶斑病新病原Stagonosporopsis vannaccii的药剂,采用菌丝生长速率法测定了啶酰菌胺等8种杀菌剂对广西贺州分离菌株GHZS80、GHZS21、GHFC63、GHFC54菌丝生长的抑制作用,选择毒力较高的4种杀菌剂开展田间试验,验证其实际防病效果.室内毒力测定结果表明,啶酰菌胺和氟吡菌酰胺的毒力最高,对4株供试菌的平均EC50分别为0.017、0.099 mg/L,其次是咪鲜胺(0.349 mg/L)和苯醚甲环唑(0.978 mg/L).田间试验结果表明,以50％啶酰菌胺水分散粒剂355g(每公顷有效成分用量)或41.7％氟吡菌酰胺悬浮剂65 g喷施3次对该病的田间防效较高,末次药后7 d的防效分别为71.11％、68.67％,显著高于其他田间施药处理.本研究结果可为防控由S.vannaccii引起的烟草叶斑病提供用药参考.

烟草棒孢霉叶斑病是影响烟草生产的主要叶部病害之一,为明确广西烟区该病害的病原菌及其毒素亚型,本研究对采自广西烟区的烟草叶斑病病原菌采用形态学、致病性、分子生物学进行鉴定.并利用毒素蛋白基因的特异性引物和对多种寄主植物的致病性进行毒素亚型测定.结果显示,广西烟草棒孢霉叶斑病菌为多主棒孢霉(Corynespora cassiicola),并首次鉴定、分析广西烟草棒孢霉病菌的毒素蛋白亚型,其中广西烟草棒孢霉病菌15个菌株中,14个菌株的毒素蛋白亚型为Cas0,1个菌株的毒素蛋白亚型为Cas7.结果表明,Cas0基因亚型较多,在靖西市同德乡首次发现烟草棒孢霉病菌中的Cas7毒素蛋白基因.本研究明确了广西烟草棒孢霉叶斑病病菌和病菌群体毒素亚型,可为防治烟草棒孢霉叶斑病提供基础依据.

In July 2022, large spots were observed on the leaves of tobacco in Guangxi province, China, whose shape was round and elliptical or irregular. The margins of spots were brown or dark brown with a pale yellow centre and several small black fruiting bodies. The pathogen was isolated by tissue isolation. Diseased leaves collected were cut into small pieces, sterilized with 75% ethanol for 30s and 2% sodium hypochlorite (NaCIO) for 60s, and rinsed with sterile deionized water for three times. Each air-dried tissue segment was cultured on potato dextrose agar (PDA) and incubated at 28℃ for 5 to 7 days in the dark (Wang et al. 2022). A total of six isolates were isolated, with differences in colony shape, edge type and colony colour, and aerial mycelium morphology, with the colony shape round or subrounded, and the edge rounded crenate, dentate or sinuate. The color of the colony was initially light yellow, then gradually changed to yellow and dark yellow. After 3-4 days, white aerial mycelia gradually grew up, which was peony-like or covered the whole colony, thus the color of the colony appeared white, and then gradually changed to orange, gray or nearly black, and all six isolates rarely produced conidia, which was consistent with the description of previous reports(Mayonjo and Kapooria 2003, Feng et al. 2021, Xiao et al. 2018). Conidia were hyaline, aseptate, and falcate, with the size of 7.8 to 12.9 × 2.2 to 3.5 μm. For molecular identification, the colony PCR method was used to amplify the internal transcribed spacer(ITS), actin(ACT), chitin synthase(CHS), and beta-tubulin(TUB2) loci of the six isolates using primer pairs ITS1/ITS4, ACT-512F/ACT-783R, CHS-79F/CHS-354R, and T1/Bt2b, respectively(Cheng et al. 2014). Partial sequences were amplified, sequenced, and uploaded to GenBank (GenBank accession Nos. OP484886，OP518265，OP518266，OP756065，OP756066, and OP756067 for ITS, OP620430 to OP620435 for ACT, OP620436 to OP620441 for CHS, and OP603924 to OP603929 for TUB2). These sequences had 99 to 100% similarity with C. truncatum isolates C-118(ITS), TM19(ACT), OCC69(CHS), and CBS 120709(TUB2) in GenBank. Homology matching was performed using BLAST and a phylogenetic tree was constructed using the Neighbor-Joining (NJ) method using MEGA (7.0) software based on ITS, ACT, CHS, and TUB2 sequences, which showed that all six isolates clustered in the same score as the C. truncatum. A pathogenicity test was performed with healthy tobacco infected with mycelial plugs (about 5 mm in diameter) of six isolates of C. truncatum from a 5-day-old culture, while negative controls on the other leaves were inoculated with sterile PDA plugs. All plants were placed in a greenhouse at 25℃ to 30℃ with 90% relative humidity. The experiment was conducted three times. Five days later, all inoculated leaves had diseased spots, whereas no symptoms appeared on negative controls. The same pathogen, C. truncatum, was identified from the inoculated leaves on the basis of morphological and molecular charchseristics as described above, fulfilling Koch's postulates. In this study, it is the first time to report that the anthracnose on tobacco was caused by C. truncatum. Thus, this work provides a foundation for controlling tobacco anthracnose in the future.

[目的]近年来由多主棒孢霉病菌引起的烟草棒孢霉叶斑病在广西烟区危害日益加重.为筛选出防治烟草棒孢霉叶斑病的优良杀菌剂,并针对棒孢霉病原菌对甲氧基丙烯酸酯类(QoIs)杀菌剂的耐药性进行初步探究.[方法]采用菌丝生长速率法测定10种杀菌剂对来自广西贺州、百色、河池3个烟区8株烟草棒孢霉病菌菌株的生物活性;扩增并分析了多主棒孢霉细胞色素b基因(Cytb)部分序列,以期探寻该病原菌对QoIs类的2种杀菌剂敏感性下降的分子机制.[结果]供试杀菌剂对烟草棒孢霉病菌菌丝生长均有不同程度的抑制,杀菌剂效果比较好的是咪鲜胺、氟啶胺和吡噻菌胺,EC40值分别为(0.049±0.027)、(0.063±0.045)、(0.286±0.077)mg/L.[结论]广西烟草棒孢霉叶斑病防治中杀菌剂应优先选用咪鲜胺、氟啶胺.广西烟区烟草棒孢霉病菌群体对QoIs类杀菌剂产生很高的耐药性,因此田间生产中不推荐再使用该类杀菌剂防治烟草棒孢霉叶斑病.且经试验发现多主棒孢霉抗性菌株与抗性相关的位点未出现Cytb基因突变.上述结果可为烟草棒孢霉叶斑病的有效防治提供依据,同时可为探寻烟草棒孢霉病菌对甲氧基丙烯酸酯类(QoIs)杀菌剂敏感性下降的分子机制提供参考.

为明确贵州烤烟棒孢霉叶斑病病原菌种类及生物学特性,本研究采用常规组织分离法对贵州省采集的烟叶进行病原菌分离与纯化,根据柯赫氏法则进行致病性测定,得到两个代表菌株YC1002和YC1104,通过形态学特征及ITS序列将其鉴定为多主棒孢霉(Corynespora cassiicola).生物学特性研究结果表明:病原菌在胡萝卜琼脂培养基(CA)上生长最快,在燕麦琼脂培养基(OA)上产孢量最多,最适生长温度为30℃,最适宜pH 6,菌丝致死温度为52℃ 10 min,光照对菌落生长影响不大.最适碳源为麦芽糖和可溶性淀粉,最适氮源为甘氨酸和苏氨酸.研究结果可为生产上烤烟棒孢霉叶斑病的有效防治提供一定的理论依据.