宜宾烤烟赤星病致病力分化、生物学特性及抑菌药剂筛选研究

Study on Pathogenicity Differentiation, Biological Characteristics of Alternaria alternata and Screening of the Effective Fungicides in Yibin

为了使生产上对烟草赤星病的防治更有针对性,对采自宜宾市烤烟种植区的具有典型赤星病症状的烟叶样品进行了组织分离、培养和形态特征观察。采用菌丝块创伤接种法测定分离菌株的致病性,同时采用菌丝生长速率法测定了不同致病力的菌株xs-k-1（较强）、xz-k-1（中）和xf-y-1（弱）的生物学特性及4种杀菌剂对较强致病力菌株xs-k-1的室内抑制效果。结果表明：21个菌株均属于链格孢菌,但各菌株间的致病力有明显的差异,平均病情指数为18.75-71.25,其中以中等致病力类型的菌株为主,占测试菌株的61.9%,弱致病力类型和较强致病力类型的菌株所占比例相当,未发现强致病力和不致病力菌株。在人工培育条件下,烟草赤星病菌在7-35℃的温度范围内均能生长和产孢,最适宜的生长和产孢温度为21-28℃;高湿度有利于病菌的生长和产孢,当湿度为100%时,病菌生长和产孢量最高,分别为5.83 cm和4.18×105个·m L-1;在p H值4-10的范围内该病菌均能生长和产孢,适宜p H值范围为7-8.5,其中病菌生长的最适p H值为8.5,产孢量最大的p H值为7。供试药剂的室内平板抑菌效果为：10%多抗霉素〉60%唑醚·代森联〉50%氯溴异氰尿酸〉40%菌核净,10%多抗霉素的EC50为15.182μg·m L-1。

To control Alternaria alternata with strong points, pathogen was isolated from the tobacco leaves with typical brown spot symptom. And the pathogen was cultured and the characters was observed. The pathogenicity of isolates was evaluated by mycelium block traumatic inoculation methods. The biological characteristics of representative isolates xs-k-1 （relatively strong）, xz-k-1 （mod- erate） and xf-y-1 （weak） with various pathogenicity were determined by using hyphal growth rate method. Moreover, the inhibition of 4 fungicides for relatively strong pathogenicity isolate xs-k-1 was investigated. The results showed that all of the 21 isolates were A. alternata, but the pathogenicity was different among different strains, and average disease index varied from 18.75N71.25. And the moderate virulent isolates distributed dominantly, accounting for 61.9%, the proportion of weak and relatively strong virulent type was the same, neither strong nor nonpathogenic. On PDA medium, mycelial can grow and spore in the temperature range of 7N35 ℃, with the optimum growth and sporulation occurring between 21 -28 ℃. The high humidity was favorable for mycelial growth and sporula- tion, the growth and sporulation reached the highest under 100% RH, 5.83 cm and 4.18x 105 individual, mL-1, respectively. Mycelial can grow and spore in the pH range of 4-10, and the suitable pH was 7-8.5, with the optimum growth pH 8.5, the optimum sporula- tion pH 7. The inhibition effects of different fungicides on A. alternata were 10% polyoxin 〉 60% pyraclostrobin ＆ metiram 〉 50% chloroisobromine cyanuric acid〉 40%dimetachlone, and 10%polyoxin ECs0 values was 15.182 μg·m L-1.