Screening of maize inbred lines for resistance to Turcicum leaf blight under artificial inoculation

Abstract:

Take an average maize farmer in Kenya's Rift Valley: during the 2019 long rains, Turcicum Leaf Blight (TLB) wiped out 40% of the standing crop in some fields before fungicide applications could respond. That kind of sudden loss is the everyday face of a disease caused by Exserohilum Turcicum (Pass.) Leonard and Suggs, and it is why resistant germplasm matters more than reactive chemistry. This research screened 60 maize inbred lines under artificial inoculation at the Damodar Valley Institute research farm during the 2022 and 2023 long-rains seasons. Inbreds were evaluated on a 1-9 severity scale, classified into six resistance groups, and ranked by area under the disease progress curve (AUDPC). One inbred (CM 212) was rated highly resistant (severity 1.2-1.8, AUDPC 42); three (CML 141, CM 107, CML 186) were resistant (AUDPC 78-112). Susceptible lines (VL 109, VL 1018) had AUDPC values above 420. Yield losses ranged from 6.1% in resistant lines to 52.4% in highly susceptible ones. CM 212 crossed with CML 141 produced an F1 hybrid that retained resistance at AUDPC 64, confirming the dominant genetic behaviour of the resistance source. The identified resistant lines can serve as donors in Rift Valley maize breeding programmes.