Field assessment of disease resistance status of some newly-developed early and extra-early maize varieties under humid rainforest conditions of Nigeria

摘要

Periodic assessment of resistant status of genetic materials in a breeding program is an important activity to ensure its continued progress. Forty newly-developed early and extra-early maize varieties were evaluated under natural field infection conditions for two years to assess their resistance status to some common diseases prevalent in the humid rainforest agro-ecology, and to determine effect of the diseases on grain yield and other agronomic characters. The experiment was laid out using a 5 x 8 alpha lattice design with three replications. Data were recorded on flowering traits, disease scores as well as yield and yield components. Data collected were subjected to analysis of variance, correlation and regression analyses. Results revealed that the varieties were significantly different for flowering traits, as well as yield and yield components except ears per plant, ear aspect and plant aspect. For disease scores, the varieties were not significantly different except for Helminthosporum maydis. There was a differential response of the early and extra-early maize varieties under the field evaluation conditions. However, all varieties maintained their resistance level against streak, northern leaf blight, southern leaf blight and smut. Although, none of these diseases significantly reduced yield, scores for Curvularia leaf spot and rust disease significantly exceeded the resistance threshold, suggesting an urgent attention is needed for the management of the diseases before the damages reach economic threshold.