Pathogenicity of sisal brown leaf spot and associated fungal species in Tanzania: A multi-site investigation

Abstract

Sisal (Agave sisalana) and aloe, members of the Agavaceae family, are economically important crops in Tanzania, with sisal primarily grown in coastal regions and aloe distributed as wild plants. Sisal brown leaf spot (BLS) disease, initially reported in 1982, poses a significant threat to the sisal industry, impacting fiber quality and productivity. This study aimed to investigate the pathogenicity of BLS and identify the associated fungal species. Eight symptomatic sisal plants and rhizosphere soil samples were collected from farms in Morogoro, Kilosa, and Korogwe, along with one wild aloe plant from Lake Eyasi in Arusha. Conventional and molecular methods were used for pathogen isolation and identification, including colony morphology, microscopic examination, and ITS Sanger sequencing. The results revealed the presence of Alternaria species in both sisal and aloe samples and Fusarium species in soil samples. Pathogenicity tests confirmed that Alternaria species induce typical BLS symptoms in inoculated sisal plants, while Fusarium species contribute to disease severity through synergistic interactions. The study highlights the influence of environmental conditions and agronomic practices on disease incidence and severity, emphasizing the need for region-specific management strategies. This multi-site investigation provides valuable insights into the management and control of BLS disease, contributing to the development of effective control measures to enhance the productivity and sustainability of sisal plantations in Tanzania. Future research should focus on integrated disease management, soil health improvement, and collaborative efforts among stakeholders to ensure the viability of the sisal industry.