Abstract:

In order to clarify the effect of three chemicals of potassium silicate, sodium silicate and salicylic acid on the induced resistance of white clover against leaf spot, the inhibitory bioactivity and induced resistance of white clover against the pathogen of leaf spot by three chemicals, and the changes of defense enzyme activities were tested in vitro and vivo experiments and with biochemical methods, respectively. The results showed that the inhibitory effects of potassium silicate, sodium silicate and salicylic acid on the pathogen of Alternaria azukiae were weak at the concentration of 25 μg·mL^-1, and the rates of inhibition was less than 4.59%, whereas the induced resistance effects of white clover to leaf spot were higher than 45.00% at the concentration of 25 μg·mL^-1. Moreover, the activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL) in white clover leaves increased significantly, and the maximum activity was on the fifth day except the maximum activity of PPO on the third day after treated with potassium silicate and sodium silicate. The induced resistance activity of white clover to leaf spot were 72.00% at the seventh day after treated with three kinds of chemicals in field experiments. However, the inhibitory effect decreased significantly after fourteen days in comparison to the results from seven days, and the minimum was 23.08%. In conclusion, the three chemicals at a concentration of 25 μg·mL^-1 were able to stimulate the PPO, POD and PAL activities associated with the disease resistance in white clover leaves. Our results indicate that the chemicals of potassium silicate, sodium silicate and salicylic acid have potential induction effect on the resistance of white clover to leaf spot.

Key words: Chemicals, White clover, Alternaria azukiae, Induced resistance

摘要：

为了探明硅酸钾、硅酸钠、水杨酸对白三叶草（Trifolium repens）抗叶斑病的诱导效果，采用离体、活体试验及生物化学方法测定了3种化学物质对白三叶草叶斑病的室内抑菌活性、诱导抗病效果、防御酶活性及田间诱导防病效果。结果表明：浓度为25 μg·mL^-1时3种化学物质的抑菌率较低，最高仅为4.59%，但诱导抗病效果较高，均在45.00%以上；叶片中多酚氧化酶（PPO），过氧化物酶（POD），苯丙氨酸解氨酶（PAL）活性均有明显增加，除硅酸钾、硅酸钠诱导处理的PPO在第3 d达到峰值外，其他化学物质诱导处理的酶活性均在第5 d达到最大值；田间处理7 d后3种化学物质诱导防病效果均达到了72.00%以上；处理14 d后有所降低，最低为23.08%。综上所述，浓度为25 μg·mL^-1的3种化学物质能够激发白三叶草叶片中与抗病性相关的PPO，POD和PAL活性，对白三叶草抗叶斑病均有较好的诱导防病作用。

关键词: 化学物质, 白三叶草, 叶斑病, 诱导抗病性