昆诺阿藜链格孢叶斑病病原及其生物学特性

为明确昆诺阿藜链格孢叶斑病病原,在山西省昆诺阿藜种植区采集典型症状的标本分离病原菌,选择代表性菌株LGB-b和LGB-h对其形态学、分子生物学、致病性及生物学特性进行了研究。综合形态学和多基因系统发育(Alt a 1、endoPG 和OPA10-2)分析,确定昆诺阿藜链格孢叶斑病病原为Alternaria alternata。致病性测定发现接种6 d后病斑呈灰绿至黄绿色,表面具有灰棕至灰褐色霉层,周围具黄绿色晕圈,与田间症状基本一致。菌株LGB-b和LGB-h均可侵染昆诺阿藜、藜和台湾藜。菌株LGB-b菌丝生长的最适培养基为V8 蔬菜汁琼脂培养基(V8)、温度为25-30 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为6-7。菌株LGB-h菌丝生长的最适培养基为马铃薯胡萝卜琼脂培养基(PCA)、温度为20-25 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为7-8。

Biological characteristics of the pathogen causing Alternaria leaf spot on quinoa

Specimens with typical Alternaria leaf spot symptoms on Chenopodium quinoa were collected in the cultivation area of quinoa in Shanxi Province. The representative isolates LGB-b and LGB-h were tested for verifying pathogenicity and the classification status by using molecular characteristics (Alt a 1, endoPG, and OPA10-2) combined with morphological identification. The results indicated that the quinoa Alternaria leaf spot is caused by Alternaria alternata. Pathogenicity test results showed that the leaves showed typical symptoms in 6 days after inoculation, which matched the symptoms in field, manifesting gray-green spot, grey-brown mould, and yellow-green halo. Isolates LGB-b and LGB-h could infect C. quinoa, C. album, and C. formosanum. The influence of culture medium, temperature, water activity (a_w), and pH on the growth of representative isolates was studied. It was found that the most favorable medium for growth of mycelia of isolate LGB-b was V8, and the most suitable temperatures were 25-30 °C. The a_w higher than 0.98 and pH 6-7 were optimal for both mycelia growth and conidial germination of isolate LGB-b. For growth of mycelia of isolate LGB-h, the most favorable medium was PCA, the most suitable temperatures were 20-25 °C, the optimum a_w was higher than 0.98, and the optimum pH was 6-7. The a_w higher than 0.98 and pH 7-8 were optimal for conidial germination of isolate LGB-h.