Improved Methodologies to Inoculate Fusarium spp. in Coffea canephora.

Abstract

Stem canker of coffee (SCC) is caused by Fusarium solani, F. decemcellulare, and F. lateritium, which induces symptoms such as cankers, wilting, yellowing, and dieback of plagiotropic and orthotropic twigs, leading to the death of the coffee plants. The absence of a standardized inoculation method to assess the disease hampers the development and implementation of effective strategies to manage and mitigate the impact of SCC. This study evaluated the efficacy of three inoculation methods in inducing SCC, and it was carried out in both laboratory and greenhouse conditions. The conidial inoculation on leaf disks (CILD) method involved applying a spore suspension (1 × 10⁶ spores ml^-1) of F. solani, F. decemcellulare, and F. lateritium to foliar disks from young and fully expanded leaves. The mycelial inoculation in injured stems (MIIS) method utilized the mycelial plug of F. solani, which was inserted in longitudinal cuts of clones LB1 and CV02 seedlings. In the root immersion conidial inoculation (RICI) method, seedling roots of clones LB1 and CV02 were cut 1 cm above the root cap and immersed in a spore suspension of F. solani (1 × 10⁶ spores ml^-1). Each treatment was evaluated daily for disease symptoms and signs of F. solani. The CILD approach proved to be an excellent time-saving tool in this investigation, and MIIS the most efficient to induce SCC symptoms. After 8 to 11 postinoculation days, wilting, yellowing, necrosis in the inoculated region, cankers, and signs of F. solani were observed on studied clones. The RICI method induced yellowing only 180 days after inoculation.