Molecular diagnosis of sorghum anthracnose disease from selected farmers' fields in Uganda

Abstract

Sorghum the second most important cereal crop in Uganda is greatly challenged by anthracnose, a disease that appears towards its harvest. Despite the various control strategies being applied to curb down this detrimental disease, Colletotrichum sublineolum keeps on tremendously attacking sorghum fields and this is ably due to improper diagnosis due to its high pathogenic variability nature. And thus, it is very important to accurately carry out diagnosis for proper fungal disease management through incorporation of molecular techniques even though the diagnosis based on the external symptoms is already made to a satisfactory level. In this study, sorghum plants from farmers’ fields in selected districts of Uganda were examined for presence of anthracnose symptoms. Infected leaves showing typical symptoms for the disease were collected and taken to the laboratory for further analysis. The most predominant fungus with characteristics of Colletotrichum species on Potato Dextrose Agar (PDA) were isolated to form pure cultures whose growth were recorded. DNA was extracted from the samples using the standard CTAB extraction protocol and quantified. The samples were then subjected to the Polymerase Chain Reaction (PCR) using the ITS primers. The samples, which showed clear bands of ~550bp when cast in a gel and observed under UV light, were further taken for sequencing. Molecular identities of the fungal isolates were found using the Basic Local Alignment Search Tool (BLAST) on the National Centre for Biotechnology Information (NCBI) databases. Only the sequence obtained from the isolate from Kitgum district was 99.13% similar to Colletotrichum sublineolum. Thus, this study showed that it is important to carry out molecular diagnosis regardless of the seemingly satisfactory visual symptom diagnosis.