Efficacy of Selected Entomopathogenic and Endophytic Fungi in the Management of Late Blight and Fusarium Wilt of Tomato in Kenya
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Date
2025-06
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Kenyatta University
Abstract
Entomopathogenic and endophytic fungal-based biopesticides are known to effectively and sustainably control pests and diseases while simultaneously improving crop growth and yield. However, their potential in managing Fusarium wilt and Late blight diseases of tomatoes in Kenya is not well exploited. This study therefore evaluated nine fungal isolates from four genera: Metarhizium, Beauveria, Trichoderma, and Hypocrea, for their effectiveness against Fusarium oxysporum f. sp. lycopersici (FOL) and Phytophthora infestans in vitro. Four potent endophytes (Trichoderma asperellum M2RT4, Hypocrea lixii F3ST1, Trichoderma atroviride ICIPE 710 and Trichoderma harzianum KF2R41) were found to effectively inhibit the pathogens mycelia radial growth. These endophytes were further tested for their ability to reduce the incidence and severity of Fusarium wilt and Late blight; and their ability to enhance tomato (Solanum lycopersicum L.) growth and yield under greenhouse. The defense response of endophytically-colonized tomato plants was further assessed upon exposure to the FOL pathogen by quantifying the level of defense gene expression using quantitative polymerase chain reaction (qPCR). In vitro assays showed that endophytes were more effective than entomopathogenic fungi (EPF) in inhibiting and suppressing FOL and Phytophthora infestans mycelial growth. Endophyte Trichoderma asperellum M2RT4 exhibited the highest suppression and inhibition of FOL with a 99.61% inhibition rate, followed by Hypocrea lixii F3ST1 (90.5%), and Trichoderma harzianum KF2R41 (86.84%) (P<0.001). On the other hand, endophyte Trichoderma atroviride ICIPE 710 had the highest suppression and inhibition of Phytophthora infestans, followed by Hypocrea lixii F3ST1 (P<0.001). Of all the assessed EPF, Metarhizium anisopliae ICIPE 20 had the highest inhibition rate of FOL and Phytophthora infestans mycelial with 40.63% and 47.65% inhibition, respectively, while the lowest inhibition rate of 27.05% and 39.15% % of FOL and Phytophthora infestans mycelia growth, respectively, was obtained in the dual culture of FOL and Beauveria bassiana ICIPE 706, and in the dual culture of Phytophthora infestans and Metarhizium anisopliae ICIPE 665. These four endophytes colonized all parts of the tomato plant with the highest colonization rate in roots (P<0.001). In vivo assays showed endophytic colonization significantly reducing the incidence and severity of Fusarium wilt and Late blight disease in tomato plants compared to non-endophytically colonized tomato plants (P<0.05). Furthermore, endophytically-colonized tomatoes showed improved plant growth parameters and increased tomato yield compared to non-endophytically colonized tomato plants (P<0.001). Moreover, Trichoderma asperellum M2RT4-colonized tomatoes significantly displayed increased expression of tomato defense genes than in un-inoculated plants (P<0.05). Overall, our findings demonstrated Hypocrea lixii F3ST1 and Trichoderma asperellum M2RT4 as the most effective biocontrol agents against Fusarium wilt disease, while Trichoderma atroviride ICIPE 710 was the best at controlling Late blight disease. Besides, the high expression of pathogenesis-related defense genes TomoPR1 and TomPR2 as well as TomLoxC and SIWRKY4 genes in tomato plant endophytically colonized by Trichoderma asperellum M2RT4 highlights the potential of this endophyte in enhancing the plant's ability to defend against Fusarium wilt pathogen. Thus, the outcomes of this study underlined the potency of underutilized entomopathogenic and endophytic fungi in sustainably reducing tomato yield losses due to Fusarium wilt and Late blight diseases.
Description
A Thesis Submitted in Partial Fulfillment of the Requirement for the Degree of Master of Science in Crop Protection (Plant Pathology Option) in the School Agriculture and Environmental Sciences, Kenyatta University, June 2025.
Supervisors
1. Waceke Wanjohi
2. Namikoye Everlyne Samita