BbHet1 also had several unique morphological features: beige conidia, unidentified clear drops on the surface of mycelial mass, and a powdery colony. The production of the drops and their role are not clearly understood. The drops may contain components such as organic acid, e.g. bassiacridin, bassianin, oxalic acid, oosporein, or cyclosporins

A and C (Russell & Paterson, 2006). Fast mycelial growth (as found for strain BbHet2) is an attractive feature for biological control when applied to the surface of soil or pests with short life cycles. It is critical that hyphal penetration should be established before the outer layer (epicuticle) of insect cuticle with conidia is discarded. It is more essential for fast-growing arthropods,

Regorafenib cost such as aphids, thrips, and mites. Fast mycelial colonization in soil can increase the frequency of contact of target insects, CHIR-99021 possibly resulting in swift killing of insects and less damage to crops. BbHet1 may also have the advantage that a higher yield of conidia is produced compared with the original isolates, which is cost-effective in mass production methods. If there is no significant change in virulence, pairing could be used as a tool for manipulate the yield of fungal conidia. Consideration should be given to the relationship between conidial thermotolerance and their RDV (darkness of conidia) which was observed under the microscope. A high density of thermotolerance-related materials could be accumulated in BbHet2 conidia, given the high RDV value. Physiologically, thermotolerance is closely related to the accumulation of heat shock proteins

(HSP) required for heat tolerance and polyols and trehalose in fungi (Hallsworth & Magan, 1996; Tereshina, 2005). In general, the expression of HSPs occurs in response to temperature, oxidative stress, osmotic stress, nutritional starvation, exposure to weak organic acids, ethanol or low pH (Zahringer et al., 1997; Williams & Hallsworth, 2009; Chin et al., 2010). HSPs are synthesized during conidiation for maintenance of conidial viability. HSPs are divided into several families by their molecular mass: 100-, 90-, 70-, and other small Adenosine HSPs, such as HSP 30 and ubiquitin (8 kDa) (Tereshina, 2005). The predominant polyol in B. bassiana is mannitol, which protects cells by scavenging toxic oxygen intermediates from heat, osmotic, and oxidative stress (Hallsworth et al., 2003; Ruijter et al., 2004). However the low-molecular weight polyols, glycerol and erythritol, are more effective in stress adjustment than higher-molecular weight compounds such as mannitol (Hallsworth & Magan, 1996). Trehalose is accumulated in idiophase in the process of fungal cell differentiation, when inhibition of growth processes is observed (Tereshina, 2005). The expression of the trehalose synthase genes is regulated by heat shock, osmotic stress, and nutritional starvation (Reinders et al., 1997).