LAUSR

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 molecularly identified and characterized in terms of conidial germination rate, mycelial growth, conidial yield and their endophytic activity. 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 (Naturalis ®) (70.7%). The LC50 bioassays revealed that only the B12 isolate had a significantly lower LC50 value (5.4 x 105 conidia mL-1 ) than BNat strain (5 x 106 conidia mL-1 ). The heat tolerance screening test (1h of exposure to 45°C) allowed us to select isolates B3, B7, B9 and B12 whose germination rates ranged from 57.5 to 80.1 % after 24h incubation at 25°C, all significantly higher than strain BNat (22.1%). 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 five weeks after root inoculation. On the basis of its potent toxicity and thermotolerance, isolate B12 is a good candidate for further development as a biopesticide for use in IPM strategies for aphid control. This article is protected by copyright. All rights reserved.