Identification of diagnostic markers for Fusarium xylarioides, the cause of coffee wilt disease in Uganda

Abstract

Fusarium xylarioides Steyaert is the causative agent of coffee wilt disease, scientifically known as trecheomycosis. This pathogen has two races, each specific to a particular coffee species; race 1 is pathogenic to Robusta coffee and race 2 to Arabica coffee in Ethiopia. The pathogen undergoes both sexual and asexual stages in its life cycle which occur in freshly infected and dying trees respectively. The sexual stage is controlled by two mating type genes designated as ‘male’ or MAT-1 and ‘female’ or MAT-2. The disease is the most devastating disease of Robusta coffee with economic loss of $34 million in 2019/2020. One of the most limiting factors in the control and management of the disease has been poor diagnostics relying squarely on microscopy and field symptoms which cannot be used to authenticate the pathogen from the soil and asymptomatic plants. The present study therefore aimed at identifying molecular and serological targets for detecting and diagnosing the pathogen as well as its mating types. This was achieved by identifying a 27kDa protein as the serological detection target and elicited specific antibodies to the pathogen. The molecular PCR based target was identified based on Translation Elongation Factor (TEF - 1α) gene and sequence characterized amplified region (SCAR), while for the mating types were based on the respective mating type genes sequences obtained in silically from NCBI database. Pictorial documentation of cultural and morphological characteristics for both mating types as a diagnostic reference in laboratories lackingPCR facility was also done. In conclusion, the study has provided both molecular and serological markers for Fusarium xylarioides. There is however need to (i) develop quantitative PCR (qPCR) to quantify the pathogen in soil and plant parts (ii) elucidate the role of the diagnostic protein in the CWD pathogen etiology.