Effect of Purple Blotch Disease on Major Onion Varieties Grown in Uganda

Iliya Mohammed1*, Perpetua Ipulet1, Africano Kangire2, Sanusi Muhammad3, Arthur Kajungu Tugume1, Shahasi Athman1 and Patrick Mucunguzi1

1Department of Plant Sciences, Microbiology, and Biotechnology, College of Natural Sciences, Makerere University Kampala Uganda

2National Crops Resources Research Institute (NaCRRI), National Agricultural Research Organization (NARO), Uganda

3Usmanu Danfodiyo University, P.M.B. 2346, Sokoto Nigeria

*Corresponding author: iliyamohd13@gmail.com, doi.org/10.55639/607.2636


After tomato, onion (Allium cepa) is the second important culinary vegetable in Uganda. Purple blotch disease affects productivity worldwide, with up to 100% losses. Eight onion varieties are grown in Uganda but no screening for resistance to this disease had been done. The objective of this study was to identify resistant varieties and establish effects of the disease on productivity. The Pathogen strains were obtained from three key onion producing regions: Mbale, Kabale and Kasese. Screen house experiments were conducted using six varieties: Bombay red, Hazera, Hybrid, Red coach, red creole and Tanzania. Trays 76 cm length x 36 cm breadth was used for the experiment. Each tray was planted with 25 seeds at 4-5 cm depth in sterile soil, and watered as required for 21 days. The seedlings were transplanted and inoculated with two virulent pathogen strains from each study region. After six weeks, disease severity was rated following 0-5 Lodha (1976) scale; Percent Disease Index (PDI) was calculated. Growth parameters: plant height, leaf length and number; bulb diameter, fresh and dry weight were recorded. Results indicated that none of the varieties showed immune resistant, moderately resistant or highly susceptible response to the disease: ratings 0, 1, 2 and 5 respectively. Red coach, Red creole and Hazera expressed Moderate susceptible response (Rating 3); Bombay red, Hybrid and Tanzania showed susceptible response (Rating 4). Tanzania was the most susceptible to all isolates with Kb17 giving the highest PDI and Red coach was the least affected with lowest PDI of 16.7. All the growth parameters were affected significantly by the disease (P < 0.05), and showed a considerable reduction compared with the control experiment. In conclusion, Red coach, Hazera and Red creole were recommended to farmers for planting.


Alternaria porri, Contamination, Disease, Productivity, Resistance, Screen house