《环境昆虫学报》

为了明确球孢白僵菌Beauveria bassiana 3菌株TST05、FDB01、SYN01对栗实象甲老熟幼虫的感染、致死率、致死中时、以及胞外蛋白酶、几丁质酶、脂肪酶的活性与毒力的关系，本研究采用3个菌株的孢子悬浮液（1.0×100000000孢子/mL），浸虫法感染栗实象甲幼虫，统计连续8 d的校正死亡率；以栗实象甲幼虫的虫体作为菌株的唯一碳源制备液体培养基，测定培养过程中各菌株的脂肪酶、几丁质酶、类枯草杆菌蛋白酶（Pr1酶）连续8 d的酶活性变化。结果表明，球孢白僵菌3个菌株TST05、FDB01、SYN01感染栗实象甲幼虫后，1-4 d内表现出染病和死亡的症状，连续8 d累积校正死亡率分别为40%、44.4%、62.22%，菌株SYN01对栗实象甲的致死率最高，与其他两菌株的差异显著；菌株TST05、FDB01、SYN01的Pr1酶活性最大峰值分别为（175.56±0.7）U/mL、（172.74±2.32）U/mL、（195.71±5.41）U/mL。几丁质酶活性最大峰值分别为（12.58±0.58）U/mL、（13.06±1.16）U/mL、（15.12±0.32）U/mL。都是菌株SYN01的酶活性最大，而TST05和FDB01之间差异不显著；球孢白僵菌3个菌株的Pr1酶、几丁质酶、脂肪酶在8 d内的酶活性平均值与染菌幼虫8 d累积校正死亡率的线性回归方程分别为y=0.4641x+122.45（R2=0.8854）、y=0.034x+10.473（R2=0.9328）、y=0.0354x+2.4586（R2=0.1201），说明菌株的Pr1酶和几丁质酶活性与幼虫死亡率之间呈显著的线性相关，而菌株的脂肪酶活性与菌株对幼虫的致死率不具有线性关系。综合分析，菌株SYN01可以作为生物防治栗实象甲的病原菌种；Pr1酶与几丁质酶的活性可作为菌株的毒力因子。

英文摘要:

This research is to explore the infection symptoms, lethallty rate, the median lethal time (LT50)of the larvae of Curculio davidiinfected with the three strains of Beauveria bassiana (TST05, FDB01 and SYN01), and to explore the relationship between the activities of extracelluar enzymes and virulence of the three strains. The following methods were used. The C. davidi were infected by immersing the insects with conidial suspension (1.0×100000000conidia/mL)of the three strains. The corrected lethallty rates of the larvae were recorded every day. The baked dry larvae were used as the sole carbon source in the medium for fungal culturing, and the activities of threes extracellular enzymes, including lipase, protease (Pr1)and chintinase produced by the three strains were determined. The results showed the diseased symptoms and death of larvae started in 1-4 d after inoculation, and the cumulative mortality on 8 d of TST05, FDB01 and SYN01 were 40%, 44.4% and 62.22%, respectively. In which, the SYN01 strain caused the highest mortality rates of the larvae and showed significant difference compared to the strains TST05 and FDB01. The maximum peak values of Pr1 enzyme activities of the strains TST05, FDB01 and SYN01 were (175.56±0.7)U/mL, (172.74±2.32)U/mL and (195.71±5.41)U/mL, respectively. The maximum peak values of chitinase activity of the three strains were (1258±0.58)U/mL, (13.06±1.16)U/mL and (15.12±0.32)U/mL, respectively. The Pr1 activities and chitinase activity of strain SYN01 were the highest in the three strains. And no difference existed between TST05 and FDB01. The relationships between the average values of Pr1 activity, chitinase activity and lipase activity of three strains in the period of 8 d and to the cumulative mortality of the infected larvae were analyzed, and the linear equations were y=0.4641+122.45 (R2=0.8854), y=0.034x+10.473 (R2=0.9328), y=0.0354x+2.4586(R2=0.1201), respectively. It is indicated a significant linear relationship between Pr1 activity and chitinase activity of the strains and the larval mortality. Based on comprehensive analysis of the results, the strain SYN01 can be considered as a better pathogenic fungus for biological control of Curculio davidi larvae Pr1 and chitinase activity can be used as virulence index for strain choice.

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