Reoccurring wilt of cotton, uncovering the pathogenesis of Eutypella species

Abstract

The reoccurring wilt disease is a relatively new name to the Australian cotton industry. This study confirmed the finding that the Eutypella species causing the reoccurring wilt disease is a new and previously unidentified fungal species. Genetic characterisation revealed four novel species of the genus Eutypella within the Diatrypaceae family, causing the disease. Along with the progress in characterisation of these novel species, it is important to understand their etiology and pathogenesis. Through a series of field and glasshouse trials, we have attempted to uncover the pathogenesis and dispersal mechanism of this disease. It was found that the infected crop residue plays an important role in carrying over the disease inoculum for the next season. The wounding of plant tissue appears to serve as a pathway for fungal inoculum to enter vascular tissue, as evidenced by the disease caused by the piece of growth media (PDA) with Eutypella mycelium when applied to a stem wound incision. On the contrary, such mycelium grown on the PDA media did not cause any disease when added to the soil close to a cotton stem without plant injury. It was also determined that the seed from infected plants doesn't transmit the disease to the next generation, confirming it’s not seedborne. Field-based research is underway to understand the dispersal pathway of the pathogen further, as the search for aerial spores continues with the help of passive spore traps deployed in several cotton fields.