A New Isolate Beauveria bassiana GxABT-1: Efficacy against Myzus persicae and Promising Impact on the Beet Mild Yellow Virus-Aphid Association

Within the context of ecofriendly alternatives to neonicotinoids, we explored the direct and endophytic potential of two <i>Beauveria bassiana</i> isolates, GHA from BotaniGard and the new endemic isolate GxABT-1, against the <i>Sugar Beet Mild Yellow Virus</i> (<i>BMYV</i>)-<i>Myzus persicae</i> pathosystem. A mortality rate of 96 and 91% was registered after 8 days of treatment with GHA and Gx-ABT-1, respectively. To assess the endophytic impact, sugar beet seeds were treated, and the ability of the fungi to colonize the plant was assessed and correlated with the aphids' (1) life cycle, (2) attraction towards the plants, and (3) ability to transmit BMYV. Both fungi colonized the plants, and the GxABT-1 isolate impaired the aphids' life cycle. <i>Myzus persicae</i> were more attracted to leaf discs from non-treated plants than to the fungal-treated ones. Interestingly, when the choice test dealt only with the fungal treatments, aphids were more attracted to leaves from plants harboring Gx-ABT-1 than those with GHA. Moreover, no significant impact was observed for BMYV transmission despite the slight decrease in the viral load in GxABT-1 isolate-treated plants. Our findings constitute a baseline to delve more into the performance of the new endemic isolate <i>B. bassiana</i> in other pathosystems using different treatment methods.