Abstract

Stem rust (Puccinia graminis) is a disease that globally has unceasingly threatened wheat. This study aimed to evaluate the response of 120 wheat varieties to stem rust under artificial inoculation for 3 seasons at Kenya Agricultural and Livestock Research Organization, Njoro. Resistance was quantified using the area under disease progress curve (AUDPC) and final disease severity with varieties exhibiting ≤300 and ≤30%, respectively considered resistant. Evaluation of Kenyan wheat varieties for yield and rust resistance is important; this study showed that 8.5 and 7.14% of varieties released in the 1920 and 1940s showed a disease severity of ≤30% across all seasons. In varieties released in the 1970s, 41.42% exhibited stem rust severity of ≤30%. Only 17.14% of varieties released in the 1990s, showed stem rust severity of ≤30%. Between the off-season of 2021 and the main season of 2022 varieties exhibiting AUDPC > 500 surged from 5 to 43. A response of 0 – trace (TR) observed on Kenya (K.) Cheetah, suggests the variety has resistant genes to the prevailing stem rust races. Varieties Mentor, K. Sungura and K. Leopard released in the 1960s, consistently showed a disease reaction of 0 to 10 moderately resistant (MR) across the seasons. This study suggests there is variable resistance amongst old Kenyan varieties.

Key words: Puccinia graminis, artificial inoculation, Kenyan wheat varieties, area under disease progress curve, final disease severity.