Gulzar Sehrish, Usman Muhammad, Wakil Waqas, Gulcu Baris, Hazir Canan, Karagoz Mehmet, Hazir Selcuk, Shapiro-Ilan David I
Department of Entomology, University of Agriculture Faisalabad 38000, Punjab, Pakistan.
Duzce University, Faculty of Arts and Sciences, Department of Biology, Duzce, Turkey.
J Invertebr Pathol. 2020 Sep;175:107452. doi: 10.1016/j.jip.2020.107452. Epub 2020 Aug 5.
Environmental factors such as temperature and desiccation impact the survival and efficacy of entomopathogenic nematodes (EPNs). Most studies on environmental tolerance have focused on EPNs applied in aqueous suspension. Another approach for EPN application is via infected host cadavers. Emergence in host cadavers is also more representative of nematodes in natural populations. In prior studies, certain advantages in fitness have been observed with the cadaver application approach relative to aqueous application, yet the impact of environmental stress on these approaches requires investigation. In this study, we compared the effects of various temperatures (heat and cold) and desiccation intervals (48 and 72 hr) on the survival, virulence and reproductive capacity of Heterorhabditis bacteriophora and Steinernema glaseri when applied via cadaver versus aqueous suspension. In the heat tolerance bioassays, following exposure to 30 °C, 35 °C and 37. 5 °C, nematodes (from both species) in the cadaver treatments exhibited higher survival, and reproductive capacity compared with aqueous application. No survival was observed above 37.5 °C regardless of species or application approach. In cold tolerance, no differences were observed between the cadaver and aqueous treatments after a sequence of exposures from 10 °C to -2 °C. In desiccation assays, following exposure to 85% relative humidity for 2 or 3 days, nematodes (from both species) exhibited higher survival and reproduction in the cadaver treatment than in the aqueous treatment, whereas no differences were observed in virulence. This is the first study to find differential stress tolerance among nematodes emerged from infected host cadavers versus those applied in aqueous suspension. Our findings indicate additional advantages when using the cadaver approach for biocontrol applications, and suggest EPNs existing in natural populations may have broader environmental tolerance than those applied via aqueous suspension.
温度和干燥等环境因素会影响昆虫病原线虫（EPNs）的存活和效力。大多数关于环境耐受性的研究都集中在应用于水悬浮液中的EPNs。EPN应用的另一种方法是通过受感染的宿主尸体。在宿主尸体中羽化也更能代表自然种群中的线虫。在先前的研究中，相对于水应用，尸体应用方法在适应性方面具有某些优势，但环境压力对这些方法的影响需要研究。在本研究中，我们比较了不同温度（高温和低温）和干燥间隔（48小时和72小时）对通过尸体与水悬浮液应用时的嗜菌异小杆线虫和格氏斯氏线虫的存活、毒力和繁殖能力的影响。在耐热性生物测定中，暴露于30°C、35°C和37.5°C后，尸体处理中的线虫（两种线虫）与水应用相比表现出更高的存活率和繁殖能力。无论物种或应用方法如何，在37.5°C以上均未观察到存活。在耐寒性方面，从10°C到-2°C一系列暴露后，尸体处理和水悬浮液处理之间未观察到差异。在干燥试验中，暴露于85%相对湿度2或3天后，尸体处理中的线虫（两种线虫）比水悬浮液处理表现出更高的存活率和繁殖率，而在毒力方面未观察到差异。这是第一项发现从受感染宿主尸体羽化的线虫与应用于水悬浮液中的线虫之间存在不同应激耐受性的研究。我们的研究结果表明，在生物防治应用中使用尸体方法具有额外优势，并表明自然种群中存在的EPNs可能比通过水悬浮液应用的EPNs具有更广泛的环境耐受性。
