Levels of genetic diversity, population structure and introduction history of the S. noctilio-A. areolatum-D. siricidicola populations in Australasia

Sirex noctilio and its symbiotic fungus Amylostereum areolatum has threatened pine plantations in Australasia, and many other countries worldwide. The biological control nematode Deladenus siricidicola has been used to manage the populations of this pest complex for over 60 years. To gain insight into any potential ‘strains’ that may contribute to variable biocontrol success the researcher further examined the reproductive rates of nematode diversity in Australia on different fungal strains and media types.  Mitochondrial (mtCOI and mtSSU rRNA) sequence data and microsatellite markers were applied in the population genetics studies. Compared to other introduced populations worldwide, lower genetic diversity was found in Australasia, and there was no structure in populations between Australia and New Zealand.

The high level of clonality in the A. areolatum population could be exploited for the management program using the nematode by rearing the nematode on the dominant clone. The behavioral study between the lineages B and D strains of D. siricidicola indicates significant variation in the reproductive rates when feeding on four different fungal strains and two media types. Lineage D strains show higher reproductive rates than the Kamona strain and other strains in lineage B, on all treatments in our trials. Taken together, the diversity identified in D. siricidicola populations in this thesis underscores the importance of post-release monitoring in the biocontrol program.

Sirex noctilio及其共生真菌Amylostereum areolatum对澳大利亚和太平洋地区以及全球的松树种植园构成了威胁。自60多年前以来，生物防治线虫Deladenus siricidicola已被用于管理这一害虫群体的数量。为了深入了解可能影响生物防治效果的潜在‘菌株’，研究者进一步考察了澳大利亚不同真菌菌株和培养基类型下线虫多样性的繁殖率。在种群遗传学研究中，应用了线粒体（mtCOI和mtSSU rRNA）序列数据和微卫星标记。与世界其他地区引入的种群相比，澳大利亚和太平洋地区遗传多样性较低，澳大利亚和新西兰之间种群结构无显著差异。A. areolatum种群中克隆性程度较高，这可以通过饲养主导克隆的线虫来利用，以管理利用该线虫的管理计划。D. siricidicola的B系和D系菌株之间的行为研究显示，在摄食四种不同的真菌菌株和两种培养基类型时，繁殖率存在显著差异。D系菌株在所有处理中均表现出比Kamona菌株和B系中的其他菌株更高的繁殖率。综合而言，本论文中识别出的D. siricidicola种群中的多样性强调了在生物防治计划中实施释放后监测的重要性。