The fungal species Trichoderma is frequently found in soil antagonizing plant-pathogenic fungi as well as parasitizing plant-pathogenic nematodes. Metarhizium species are insect-pathogenic fungi that are used throughout the world to control agricultural insect pests. Here, we determine whether the antagonism (A) of Trichoderma atroviride to Metarhizium robertsii during growth and spore formation can impact the stress biology of M. robertsii conidia. Cultures of M. robertsii were either produced without exposure to T. atroviride (control) or in the presence of T. atroviride. M. robertsii was grown in dual culture with T. atroviride on potato dextrose agar (PDA) using the following treatments: 1) Trichoderma inoculated at the same time with Metarhizium (A0); 2) Trichoderma inoculated two days after the inoculation of Metarhizium (A2); 3) Trichoderma inoculated four days after Metarhizium (A4); 4) Trichoderma inoculated 6 d after Metarhizium (A6); 5) M. robertsii grown alone on PDA medium (control); and 6) M. robertsii grown alone on minimal medium (Czapek-Dox medium without sucrose) (MM). Germination of M. robertsii conidia from all six treatments was then assessed under osmotic, oxidative, UV-B, and thermal stress. M. robertsii conidia produced on MM were the most tolerant to all stress conditions. For all stress conditions, conidia from treatments A0 and A2 were not viable. For osmotic stress, conidia produced in treatment A4 were the most tolerant, followed by conidia from treatment A6, which were both more tolerant than the control. For oxidative stress, conidia produced in both A4 and A6 treatments were similarly tolerant and more tolerant than conidia produced in the control. For thermal stress, conidia produced in treatments A4, A6, and control (PDA) were similarly heat-tolerant. For UV-B stress, conidia produced in treatments A4 and A6 were equally tolerant and more tolerant than conidia produced in the control. The germination speed of conidia produced in all treatments, A0, A2, A4, and A6 was also tested. Conidia produced on MM germinated faster than the other treatments. Conidia produced in the A4 treatment were the second fastest, followed by conidia produced in treatment A6. Both A4 and A6 conidia germinated faster than conidia produced in the control treatment. Conidia produced in the treatments A0 and A2 did not germinate in 24 h. In summary, moderate levels of biotic stress from a fungal competitor or low-nutrient conditions can enhance the stress tolerance of M. robertsii conidia.

中文翻译：

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木霉和绿僵菌之间的角力中的意外

真菌物种木霉属常见于土壤中对抗植物病原真菌以及寄生植物病原线虫。绿僵菌属昆虫病原真菌，在世界范围内用于控制农业害虫。在这里，我们确定在生长和孢子形成过程中，木霉属 atroviride 对罗伯氏绿僵菌的拮抗作用 (A) 是否会影响罗伯氏分生孢子的胁迫生物学。M. robertsii 的培养物是在没有接触阿曲病毒杆菌（对照）的情况下产生的，或者是在存在阿曲病毒杆菌的情况下产生的。M. robertsii 与 T. atroviride 在马铃薯葡萄糖琼脂 (PDA) 上使用以下处理进行双重培养： 1) 木霉同时接种绿僵菌 (A0)；2)接种绿僵菌(A2)两天后接种木霉；3)绿僵菌后4天接种木霉(A4)；4)绿僵菌(A6)后6天接种木霉；5) M. robertsii 在 PDA 培养基上单独生长（对照）；和 6) M. robertsii 在基本培养基（不含蔗糖的 Czapek-Dox 培养基）（MM）上单独生长。然后在渗透、氧化、UV-B 和热应激下评估来自所有六种处理的 M. robertsii 分生孢子的萌发情况。在 MM 上产生的 M. robertsii 分生孢子对所有压力条件的耐受性最强。对于所有胁迫条件，来自处理 A0 和 A2 的分生孢子不可行。对于渗透胁迫，处理 A4 中产生的分生孢子最耐受，其次是处理 A6 中产生的分生孢子，它们都比对照更耐受。对于氧化应激，在 A4 和 A6 处理中产生的分生孢子与对照中产生的分生孢子相比具有相似的耐受性并且更耐受。对于热应力，处理 A4、A6 和对照 (PDA) 中产生的分生孢子具有类似的耐热性。对于 UV-B 胁迫，处理 A4 和 A6 中产生的分生孢子与对照中产生的分生孢子具有同等的耐受性并且更耐受。还测试了所有处理中产生的分生孢子的萌发速度，A0、A2、A4和A6。在 MM 上产生的分生孢子比其他处理发芽得更快。在 A4 处理中产生的分生孢子是第二快的，其次是在处理 A6 中产生的分生孢子。A4 和 A6 分生孢子的萌发速度都比对照处理中产生的分生孢子快。在处理 A0 和 A2 中产生的分生孢子在 24 小时内没有发芽。总之，