Characterisation of an emerging banana wilt disease on East African highland bananas (musa-aaa) in central Uganda

Abstract

The genus Musa spp. is a crucial food to humans in the world, and bananas play a significant role in Uganda's socio-economic fabric. However, emerging pests and diseases threaten sustainable banana cultivation. A study was conducted in Ugandan central districts of Wakiso, Mpigi, and western districts of Mbarara, Isingiro to understand the causative agent of an emerging golden yellow leaf syndrome similar to symptoms of FOC Race 4 in Uganda between October 2023 to May 2024. The key objectives; survey banana gardens associated with golden yellow-leaf syndrome on EAHBs, collect and segregate the pathogens from the selected study districts; diagonize the pathogen related to golden yellow-leaf syndrome on EAHB in the selected districts; determine the pathogenicity of isolated pathogens on selected EAHB cultivars. Questionnaires were administered to 25 farmers to understand indigenous knowledge about the disease in the study areas. Symptomatic plant samples were collected and delivered to the laboratory for pathogen diagnosis using molecular markers. The characterized isolates were screened against selected EAHB varieties to confirm Koch’s postulates. About 88% of respondents had ever seen 'golden leaf' syndrome in their banana gardens but did not know the cause. Farmers reported symptoms starting within two years, with 64% having shared planting materials, and the disease symptoms were reported prevalent during rainy seasons. Of 21 isolates purified, 6 were positive for the 28S - 18S rRNA inter-spacer region using FocTR4 primers, and after sequencing, five of them were verified to be FON and one was FOC Race 1. Screening results showed that Sukali ndizi, and EAHB varieties were vulnerable to FON. Thus FON, a devastating pathogen of watermelons, is now pathogenic to EAHBs, a threat to farmers' livelihoods and food security in Uganda. This is the first report of this pathogen in Uganda affecting bananas, Further research is needed to map its spread and resistant sources in the banana germplasm.