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Aims: Mitochondrial fission is an essential dynamics that maintains mitochondrial morphology and function. This study seeks to determine the roles of mitochondrial fission in the filamentous entomopathogenic fungus Beauveria bassiana. Material and methods: Three fission‐related genes (BbFis1, BbMdv1 and BbDnm1) were functionally characterized via protein intracellular localization and construction of gene disruption mutants. Results: Mitochondrial localization was only observed for BbFis1 which interacts with BbMdv1, but BbMdv1 did not have interaction with BbDnm1. Single disruption mutant of three genes generated the elongated and enlarged mitochondria which could not be eliminated via the mitophagy. Three mutant strains displayed the reduced ATP synthesis and vegetative growth compared with the wild type. Three genes were involved in the early stage of conidiation and unnecessary for the late stage. However, all three genes significantly contribute to blastospore development under submerged condition, and the loss of BbMdv1 had the greatest effects compared with the losses of BbFis1 or BbDnm1. Finally, disruption of three genes significantly attenuated fungal virulence, but their mutations had different influences. Conclusions: In addition to their consistent roles in mitochondrial division and mitophagy, three fission‐related genes perform divergent roles in the development and virulence of the entomopathogenic fungus B. bassiana. Significance and Impact of the Study: This study shows that mitochondrial fission is associated with lifecycle of B. bassiana. These findings provide information for the manipulation of fungal physiology and facilitate the application of entomopathogenic fungi. [ABSTRACT FROM AUTHOR]

Aims: To produce more thermotolerable conidia of Beauveria bassiana, a well-known fungal biocontrol agent, by optimizing the medium components and culture conditions. Methods and Results: The conidia produced on media including 0·5–6% glucose, sucrose or starch as carbon source and 50–300- μg ml−1 Cu2+, Zn2+, Mn2+ or Fe3+ as additive to Sabouraud dextrose medium at 15–30°C, pH 4–8 or KCl-adjusted water availabilities were exposed to 30-min wet heat stress at 48°C. The medium components for conidial production with greatly enhanced thermotolerance included 4% glucose as optimum or 1% starch as alternative for the carbon source and ⩽50- μg ml−1 Mn2+ for the metal additive. The culture conditions were optimized as 25°C and pH 5–6. Conidial thermotolerance decreased remarkably when sucrose and Fe3+ or Cu2+ were used in the cultures, but altered slightly when 50–200- μg ml−1 Zn2+ were included. Conclusions: The tolerance of B. bassiana conidia to the thermal stress was significantly affected by the medium composition and culture conditions under which the conidia were produced. Significance and Impact of the Study: Proper treatment of small grains as mass production substrates for more glucose release and supplement of glucose or ⩽50- μg ml−1 Mn2+ are possible means to enhancing conidial thermotolerance and field persistence for improved insect control. [ABSTRACT FROM AUTHOR]

Mineral oil-based emulsifiable preparations of Beauveria bassiana (Bb) and Paecilomyces fumosoroseus (Pfr) conidia were separately applied alone or together with low rates of imidacloprid 10% WP at 4.7% (Im 1), 14.0% (Im 2), and 23.3% (Im 3) of its recommended application rate, respectively, against the greenhouse whitefly, Trialeurodes vaporariorum, on lettuce grown in the greenhouse. Besides eight fungal treatments, the three low application rates of imidacloprid in the oil-based carrier and a blank control (CK) were also included as treatments of the trials conducted in 2002 and 2003. For the 12 treatments of each trial with three replicates, 1,000-fold aqueous dilutions were sprayed twice on transplanted lettuce at a 15-day interval at a rate of ∼1.43×10 13 conidia ha -1 for each fungal treatment or at one of the low rates of imidacloprid using a backpack hand-operated hydraulic sprayer. Based on whitefly densities, mortalities, relative efficacies and percent density declines estimated from whitefly counts made at 5-day intervals, all B. bassiana and P. fumosoroseus sprays were highly effective against T. vaporariorum compared to CK and Im 1-3 in both trials. In trial 1, the estimates of whitefly density decline and relative efficacy ranged from 44 and 72% (Bb) to 79 and 90% (Pfr+Im 2-3) on day 10 after the first spray and exceeded 94% for all fungal treatments 10 days after the second spray. Similar trends in whitefly control were also achieved in the corresponding treatments of trial 2. A more desirable and faster control resulted from fungal sprays containing more imidacloprid, but none of the three low imidacoprid rates alone suppressed the whitefly population more effectively than any fungal treatment despite a varying degree of efficacy. Moreover, P. fumosoroseus tended to be more effective against T. vaporariorum than B. bassiana when applied alone or together with the same low rate of imidacloprid but the difference in whitefly control eventually achieved was not significant between the two fungal agents. Thus, the emulsifiable preparations of both fungal agents can be considered as alternatives for whitefly management and for a slightly faster control can be applied together with imidacloprid at around 15% of its common application rate. An economic balance between the efficacy of whitefly control and the ease and cost of conidial production is needed when both fungi are incorporated into whitefly management. [ABSTRACT FROM AUTHOR]

s.-h. ying and m.-g. feng. 2004. This study was to illustrate the relationship between the thermotolerance and the contents of hydrophobin-like or formic-acid-extractable (FAE) proteins in aerial conidia of Beauveria bassiana and Paecilomyces fumosoroseus produced on rice-based substrate. Survival indices of 11 isolates were separately assessed as a ratio of the viability of conidia after 3–150 min thermal stress at 48°C over that of unstressed conidia and fitted well to a survival model ( r2 ≥ 0·97). For a given isolate, the fitted model generated an LT50, the time for 50% viability loss under the stress. The LT50s of six B. bassiana isolates (10·1–61·9 min) and five P. fumosoroseus isolates (2·8–6·2 min) were correlated ( r2 = 0·81) with FAE protein contents (6·9–23·4 μg mg−1). The survival indices of a fixed B. bassiana isolate after 45-min thermal stress at 48°C were also correlated to the FAE protein contents from conidia produced on glucose-, sucrose-, or starch-based substrate (0·79 ≤ r2 ≤ 0·86). Three bands of 12·0, 15·0 and 17·5 kDa were recognized from SDS-PAGE profiles of protein extracts from different isolates or from the fixed isolate grown on the three carbon sources, but the 12 kDa was less likely related to the thermotolerance. Approximately 80% of variability in conidial thermotolerance was attributed to either 15·0- or 17·5-kDa FAE protein or both. The relationship between conidial thermotolerance and FAE protein contents implicates a new way to search for fungal biocontrol agents with more thermotolerance and environmental persistence. [ABSTRACT FROM AUTHOR]