Exploring fungal pathogens to control the plant invasive Rubus niveus on Galapagos Island San Cristobal

The Galapagos ecosystem faces threats from invasive species displacing native and endemic species. Rubus niveus (Hill raspberry) is particularly problematic invasive plant, covering approximately 30,000 hectares across the archipelago and rapidly outcompeting native vegetation. Current control methods, such as manual removal and herbicide application, have proven ineffective. This research aimed to identify endemic fungi pathogenic to R. niveus for potential population suppression. To achieve this goal, we sampled leaves, fruits, and stems of R. niveus in the agricultural areas of San Cristobal, Galapagos. Microbiome composition analysis of healthy and diseased R. niveus leaves revealed differences in fungal communities, representing a greater abundance of pathogenic genera in diseased tissue. These genera included Alternaria, Septoria, Fusarium, Colletotrichum, and Phanerochaete, representing well-known pathogens. Among 595 fungi isolated from Hill raspberry samples with lesions, 226 were tested for pathogenicity on healthy Hill raspberry leaves, resulting in five possible candidates consistently causing lesions. Further characterization through morphology and DNA analysis confirmed these candidates as Lasiodiplodia theobromae, Colletotrichum gloesporioides, Fusarium concentricum, Phanerochaete chrysosporium, and Penicillium rolfsii. Future research will explore the suitability of these fungal pathogens as biocontrol agents of invasive Hill rapberry.