Resistance of South African maize hybrids to maize streak virus

Data from maize cultivar trials at Vaalharts over a five-year period were used to evaluate the level of resistance to maize streak virus (MSV) in commercial maize hybrids, and to determine the potential value of such resistance. Maize hybrids presently grown in South Africa showed varying degrees of resistance to MSV. In general, yellow maize hybrids displayed a wide range of genetic variability, from resistant to highly susceptible, whereas white maize hybrids were mostly highly susceptible. Calculated resistance indices on a scale from 1 (resistant) to 5 (highly susceptible) proved very useful in quantifying genetically-based plant reaction to MSV infection. Hybrids ranked consistently similar, both within and throughout all seasons. The relationship between yield loss due to MSV infection and resistance indices was positively correlated.