利用腐生线虫加速替代疫木中松材线虫种群数量研究

【目的】筛选在疫木中容易定殖且能够加快树体内松材线虫种群消退的腐生线虫,在媒介昆虫羽化前大幅减少疫木中松材线虫种群数量,使得松材线虫病害的传播得到有效控制。【方法】从安徽、四川和江苏3省的部分疫区采集的疫木中分离获得8种腐生线虫。将8种腐生线虫以1、2、4倍于木块中松材线虫数量的接种量接种至疫木块中,以接种无菌水的木块为对照,分别置于15和25 ℃下培养15和30 d,分离并计数疫木块中松材线虫和腐生线虫的种群数量,分析不同接种量及温度下,接种腐生线虫对疫木中松材线虫种群数量的影响。野外条件下,将8种腐生线虫接种至松材线虫病疫木段中,接种量为2.0×10⁵~2.5×10⁵条,以接种无菌水的木段作为对照。120 d后钻取木样,150 d后捕获松墨天牛并收集蛹室周围木样,分离并计数木样中的松材线虫数量,比较接种前后疫木内松材线虫数量的变化,分析腐生线虫对疫木整体、天牛及蛹室周围携带的松材线虫种群的影响。【结果】室内接种试验表明,15 ℃培养时,在第30 天接种量为4倍的虫株JHS2处理组和接种量为1倍的虫株JHS4处理组能显著降低松材线虫的数量。25 ℃条件下培养的第15 天,3种不同接种量的虫株JHS4处理组中松材线虫减少率均显著高于对照。培养 30 d后,接种量为4倍的虫株JHS4处理木块中松材线虫减少率显著高于对照,为对照的2.9倍。野外接种试验结果表明接种虫株JHS4能加速木段内松材线虫的消亡,与对照相比,木段整体松材线虫的减少率为96%,显著高于同期对照(74%);此外,所有处理组的蛹室周围木样和羽化天牛所携带的松材线虫量均低于对照。其中,虫株JHS4处理组蛹室周围木样和羽化天牛携带的松材线虫数量最低,每克蛹室木样中携带松材线虫的数量仅为20 条,平均每头天牛携带松材线虫的数量为132条。【结论】腐生线虫能够加快疫木中松材线虫种群消退,可影响天牛蛹室及天牛所携带的松材线虫数量。利用腐生线虫对疫木中松材线虫具有一定的生防潜力,将其应用于松材线虫病的疫木除治具有技术可行性和广阔前景。

A study on the use of saprophytic nematodes to accelerate the replacement of Bursaphelenchus xylophilus in infected trees

【Objective】 In this study, we aimed to screen out saprophytic nematode strains that were easy to colonize and could accelerate the extinction rate of the Bursaphelenchus xylophilus population to substantially reduce the quantity of B. xylophilus in infected trees before the emergence of vector insects, thus effectively controlling the spread of the disease. 【Method】 Eight species of saprophytic nematodes were isolated from the infected trees, which were collected from epidemic areas in Anhui, Sichuan and Jiangsu Province. Eight species of saprophytic nematodes were inoculated into the infected wood blocks with an inoculation quantity of one, two and four times the number of B. xylophilus in the wood blocks. Wood blocks inoculated with sterile water were used as controls, which were cultured at 15 and 25 ℃ for 15 and 30 days, respectively. The quantity of B. xylophilus and saprophytic nematodes in the infected wood blocks were isolated and calculated. The effects of inoculation with saprophytic nematodes on the quantity of B. xylophilus were analyzed under the different inoculation amounts and different ambient temperatures. In the field, eight species of saprophytic nematodes were inoculated into the segments of the plague woods with the inoculation amount of 2.0×10⁵~2.5×10⁵ individuls, and segments inoculated with sterile water were used as the control. After 120 days, the wood samples were drilled. After 150 days, the Monochamus alternatus were captured and the wood samples around the pupae room were collected. The quantity of B. xylophilus collected was separated and counted. The changes in the quantity of B. xylophilus in the infected trees were compared before and after inoculation, and the effects of saprophytic nematodes on the quantity of B. xylophilus in the whole infected trees, M. alternatus and around the pupa rooms were analyzed.【Result】 The results from the indoor inoculation experiment showed that the number of B. xylophilus in the strain JHS2 and JHS4 treatment groups with four times and 1 times the inoculation amount on the 30th day could be substantially reduced when cultured at 15 ℃. On the 15th day of culture at 25 ℃, the reduction rate of the quantity of B. xylophilus in the strain JHS4 treatment group with three different inoculation doses were significantly higher than that of the control group. After 30 days of culture, the reduction rate of B. xylophilus in the treatment group which inoculated four times the inoculation amount of strain JHS4 was 2.9 times higher than that of the control group. Field inoculation results showed that strain JHS4 could accelerate the extinction rate of B. xylophilus in wood segments. Compared with the control group, the reduction rate of B. xylophilus in wood segments was 96%, which was significantly higher than that of the control group (74%) over the same period. Compared with CK, the quantity of B. xylophilus carried by wood samples around the pupa chambers and emerged M. alternatus in all treatment groups was often lower than that of the control group. The quantity of B. xylophilus carried by wood samples around the pupae chambers and emerged M. alternatus in strain JHS4 treatment group was the lowest, and the quantity of B. xylophilus carried by wood samples in the pupae chamber was 20 individuls per gram, and the average quantity of B. xylophilus carried by M. alternatus was 132 individuls per head.【Conclusion】 The saprophytic nematodes can accelerate the extinction rate of the quantity of B. xylophilus in infected trees and the pupae chamber, and M. alternatus. It is clear that the saprophytic nematodes have biological control potential for the pine wilt disease, and their application in the control of B. xylophilus has technical feasibility and broad prospects, which is worthy of further development and research.