Field Performance and Susceptibility Patterns of Ten Cassava Varieties to Mosaic Virus Disease Under Natural Infection Pressure in the Sudan Savannah, Nigeria

Abstract

Cassava mosaic disease (CMD) is the foremost viral threat to cassava production across sub-Saharan Africa, but data on varietal performance under natural infection in Nigeria’s Sudan Savannah remain scarce. This study, conducted during the 2024 rainy season at Abdullahi Fodiyo University, Kebbi State, evaluated ten improved varieties and two local landraces for their responses to natural CMD. Using a randomized complete block design with three replicates and infector rows of susceptible ‘Sarkin Fawa’ to boost inoculum pressure, disease incidence and severity were recorded bi-weekly from 2 to 12 weeks after planting (WAP) on a 1–5 scale. Results showed significant differences (P < 0.05) among varieties. The local landrace DANGWAMNATI proved most susceptible, with incidence rising from 28.57% at 2 WAP to 100% by 10 WAP and severity reaching 63.10% at 12 WAP. BAHAUSHE also displayed high susceptibility (95.24% incidence, 60.71% severity). IBA 961632 showed moderate susceptibility (47.62% incidence, 23.81% severity), while IBA 30572 exhibited partial resistance (33.33% incidence, 14.29% severity). Remarkably, six improved varieties (OBASANJO 2, GAME CHANGER, BABA 70, IBA 0505, IBA 164773, and IBA 154810) recorded zero incidence and severity throughout the trial, indicating complete field resistance consistent with CMD2 gene-mediated immunity. Symptoms in susceptible types included mosaic, chlorosis, distortion, and stunting. This work establishes clear susceptibility categories for cassava varieties under natural CMD infection in the Sudan Savannah and identifies six immune genotypes suitable for further validation and immediate promotion to farmers. The ongoing reliance on highly susceptible local landraces poses a serious risk to regional production, highlighting the critical need for accelerated replacement with improved, resistant varieties.