Selection and characterization of thermotolerant Beauveria bassiana isolates and with insecticidal activity against the cotton‐melon aphid Aphis gossypii (Glover) (Hemiptera: Aphididae)

Abstract

BACKGROUND: Cotton-melon aphid Aphis gossypii (Glover) causes severe damage mainly to cucurbits. Twenty-two Beauveria sp. isolates were simultaneously assessed for their pathogenicity and heat tolerance. The selected isolates were identified molecularly and characterized in terms of conidial germination rate, mycelial growth, conidial yield and endophytic activity. RESULTS: Screening bioassays showed that the B. bassiana isolates B3, B7, B9 and B12 were the most toxic, inducing mortality equal to or slightly higher than the commercialized strain B. bassiana BNat (70.7%). Median lethal concentration (LC 50 ) bioassays revealed that only isolate B12 had a significantly lower LC 50 value (5.4 × 10 5 conidia ml −1 ) than strain BNat (5 × 10 6 conidia ml −1 ). The heat tolerance screening test (1 h of exposure to 45°C) allowed us to select isolates B3, B7, B9 and B12 with germination rates of 57.5% to 80.1% after 24 h incubation at 25°C, all significantly higher than strain BNat (22.1%). The germination rates of all isolates decreased significantly after 2 h of exposure to 45°C, with the exception of isolate B12 which displayed the highest thermotolerance (72% germination). The four selected isolates were able to endophytically colonize cucumber leaves when applied to the foliage. Inoculation of cucumber plants with isolate B12 did not affect cucumber plant growth. However, several plant growth parameters were improved 5 weeks after root inoculation.CONCLUSION: On the basis of its potent toxicity and thermotolerance, isolate B12 is a good candidate for further development as a biopesticide for use in integrated pest management strategies for aphid control.

Metarhizium rileyi with broad‐spectrum insecticidal ability confers resistance against phytopathogens and insect pests as a phytoendophyte

“…53 Mseddi et al screened a wild strain of B. bassiana B12 that not only promoted several plant growth parameters at 5 weeks after root inoculation, but also displayed higher toxicity toward the cotton-melon aphid Aphis gossypii (Glover) than the commercialized B. bassiana BNat strain following colonization in cotton plants. 54 Some research suggests that EPF have the capacity to transfer nutrients to plants, 55,56 and the growth and virulence of EPF increased depending on the colonization of plants. 40 Thus, it is necessary to find new EPF strains that can confer plant resistance against biotic stress through endogenous colonization.…”

First record of Aspergillus nomiae as a broad-spectrum entomopathogenic fungus that provides resistance against phytopathogens and insect pests by colonization of plants

“…For example, endophytic colonization by B. bassiana and M. anisopliae in maize plants affects the fitness of S. frugiperda , and both strains negatively impact the development and fecundity of S. frugiperda ( Altaf et al, 2023 ). Sinno et al (2021) found that aphids reared on B. bassiana -treated plants for their entire lifespan were negatively affected in terms of survival and fertility in comparison with control cohorts; Mseddi et al (2022) screened a wild strain of B. bassiana B12 that not only promoted several plant growth parameters after root inoculation, but also displayed toxicity toward A. gossypii following colonization in cotton plants. Zhu et al (2023) found that B. bassiana -inoculated maize plants can influence the eggs laying selectivity of O. furnacalis females by changing plant volatile profiles; and González-Mas et al (2021) found that when the cotton was colonized by B. bassiana , they emit a different blend of volatile compounds compared to uncolonized control plants, which can affect the feeding behavior of insect pests A. gossypii , S. frugiperda , and S. littoralis .…”

Hypovirulence-associated Mycovirus Epidemics Cause Pathogenicity Degeneration of Beauveria bassiana in the Field

“…In the past, acquisition of high-virulence strains of B. bassiana has mainly involved isolation and screening of wild strains collected from the eld using biological testing, which is time-consuming and labour-intensive [74,75]. Here, we found that mycoviruses may be a key factor causing the decline of B. bassiana virulence, and virus detection could be used to exclude hypovirulent virus-infected strains, and to screen strains of wild B. bassiana with high virulence, thereby improving the e ciency of high virulence strain screening.…”