Zhao Boguang

Antifungal activities of matrine and oxymatrine and their synergetic effects with chlorthalonil

The EC50 values of matrine and oxymatrine against five forest pathogenic fungi (Fusarium oxysporum, Valsa pini, Cladosporium oxysporum, Sphaeropsis sapinea, Marssonina brunnea) were examined by bioassay methods. The results demonstrated that matrine and oxymatrine had strong inhibitory activities to the conidium germination of the tested fungi. The EC50 values of matrine for inhibiting the conidium germination of Marssonina brunnea, Cladosporium oxysporum, Sphaeropsis sapinea were 123 μg·mL−1, 272 μg·mL−1, 1133 μg·mL−1, respectively, and the EC50 values of oxymatrine for inhibiting the conidium germination of Fusarium oxysporum, Sphaeropsis sapinea were 532 μg·mL−1, 601 μg·mL−1, respectively. The hyphal growth of the fungi was also significantly inhibited by matrine and oxymatrine. The EC50 values of matrine inhibiting the conidium germination of Sphaeropsis spainea, Valsa pini, Fusarium oxysporum were 428 μg·mL−1, 535 μg·mL−1, 592 μg·mL−1, respectively. The EC50 values of oxymatrine inhibiting the conidium germination of Valsa pini, Fusarium oxysporum were 323, 618 μg·mL−1, respectively. In the synergetic tests the EC50 values of the mixtures of thiophanate methyl (or chlorthalonil) and matrine (or oxymatrine) were lower than 34 μg·mL−1 while their co-toxicity coefficients were significantly higher than 100. It indicated that the mixture of the alkaloids and the chemical had potential practical utilization in controlling certain forest fungal diseases.

Inhibitory effects of alkaloids from Sophora alopecuroids on feeding, development and reproduction of Clostera anastomosis

Alkaloids from Sophora alopecuroids were bioassayed with Clostera anastomosis for their antifeedant and growth inhibitory effects. The antifeedant rate in choice test reached 62%–86% at the dose 2.5 mg/mL, while in non-choice bioassay the rate was only 20%–29%. In choice bioassay, the antifeedant rate increased with larval instars of C. anastomosis and did not in non-choice experiment. The alkaloids also imposed a strong influence on the growth of C. anastomosis larvae, i.e., after feeding on the leaves treated with alkaloid, the larvae lost their weight, weight gain, and relative growth rate (RGR) significantly when compared with the controls. In the second day after treatment with the dose at 10 mg/mL of the alkaloid, the RGR reduced by 39.8%, and the food intake and the feces weight were respectively 57.7% and 57.4% of the controls. The approximate digestibility (AD) increased significantly, and the efficiency in converting digested food (ECD), and the efficiency in converting ingested food (ECI) decreased greatly after feeding the treated leaves. Moreover, the eggs laid per female were also inhibited by this alkaloid. The significance and prospect of the alkaloids in controlling forest insect pests were also discussed.

Mutual influences in growth and reproduction between pine wood nematode Bursaphelenchus xylophilus and bacteria it carries

The interactions between pine wood nematode and three bacterium strains isolated from the nematode, Bursaphelenchus xylophilus, which are two strong pathogenic bacterium strains, Pseudomonas fluorescens GcM5-1A and Pseudomonas putida ZpB1-2A and a weak-pathogenic bacterium strain, Pantoea sp. ZM2C, were studied. The result showed that the strong-pathogenic GcM5-1A strain and ZpB1-2A strain significantly increased fecundity, reproduction rate, and the body volume of the adult nematode. Meanwhile, pine wood nematodes significantly promoted reproduction of the two strong-pathogenic bacterium strains. However, the weak-pathogenic bacterium strain, ZM2C, completely inhibited reproduction of pine wood nematodes. Aseptic pine wood nematodes significantly inhibited reproduction of the strain ZM2C. The results indicated that mutualistic symbiosis exists between pine wood nematodes and the two pathogenic bacteria it carries. The phenomenon showed that the pathogenic bacteria carried by the nematode were not accidentally contaminated, but rather had existed as symbionts of the nematode with which it had coevoluted over a long period. The role of mutualistic symbiosis in the process of pine wilt disease was also discussed.

Electrical wave transmission in healthy black pine seedlings

Non-injurious local stimuli, such as a cold shock, and injurious stimuli, such as local burning, punctures or chemicals, were applied to study electrical wave transmission in black pine (Pinus thunbergii) seedlings. The results showed that non-injurious stimuli evoked the action potential (AP) transmission and injurious stimulation induced both AP transmission and the more complex variation (VP) transmission in the seedlings. The causes of these phenomena were discussed.