Abstract
The use of Beauveria bassiana in biological control of agricultural pests is mainly hampered by environmental factors, such as elevated temperatures and low humidity. These limitations, further amplified in a global warming scenario, could nullify biological control strategies based on this fungus. The identification of thermotolerant B. bassiana isolates represents a possible strategy to overcome this problem. In this study, in order to maximize the probability in the isolation of thermotolerant B. bassiana, soil samples and infected insects were collected in warm areas of Syria. The obtained fungal isolates were tested for different biological parameters (i.e., growth rate, sporulation and spore germination) at growing temperatures ranging from 20°C to 35°C. Among these isolates (eight from insects and 11 from soil samples), the five with the highest growth rate, spore production and germination at 30°C were tested for their entomopathogenicity through in vivo assays on Ephestia kuehniella larvae. Insect mortality induced by the five isolates ranged from 31% to 100%. Two isolates, one from Phyllognathus excavatus and one from soil, caused 50% of the larval mortality in less than four days, reaching values exceeding 92% in ten days. These two isolates were molecularly identified as B. bassiana sensu stricto by using three markers (i.e., ITS, Bloc and EF1-α). Considering these promising results, further studies are ongoing, testing their efficiency in field conditions as control agents for agricultural insect pests in Mediterranean and Subtropical regions.
Highlights
Global climate change poses new challenges to agricultural production [1], increasing crops’ vulnerability to plant diseases and pests mainly as a consequence of physiological stresses [2], and the expansion of insects and diseases into higher latitudes [3]
The keystone adaptive strategy relies on integrated pest management (IPM), which depends upon different integrated practices starting from an accurate estimation of the pest abundance based on monitoring and working towards the adoption of biological control strategies to reduce of conventional pesticide application [8]
Mycoinsecticides, mainly consisting of the fungal pathogen Metarhizium anisopliae (Metschn.) Sorokın and Beauveria bassiana Balsam are a fundamental component of these biological control strategies [9,10]
Summary
Global climate change poses new challenges to agricultural production [1], increasing crops’ vulnerability to plant diseases and pests mainly as a consequence of physiological stresses [2], and the expansion of insects and diseases into higher latitudes [3]. The optimal growth temperature of B. bassiana is between 25 ̊C and 28 ̊C [16], though it has been demonstrated that some isolates are able to grow at a higher temperature (~30 ̊C) with highly reduced activity and may not survive at 34 ̊C [17,18] To overcome this limitation, a possible strategy has been developed, which relies on genetic improvement of the fungus in terms of its tolerance to oxidative stress was developed [19,20]; this approach suffers regulatory and societal limitations related to the use of genetically modified organisms [21]. A possible alternative strategy consists of mass screening of fungal isolates for the target phenotype, a successful strategy in the case of UV tolerance [22]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
