Susceptibility of maize hybrids to grey leaf spot under two tillage systems in South Africa

Grey leaf spot (Cercospora zeae-maydis Tehon and E.Y. Daniels) has seriously decreased the yields of maize in KwaZulu-Natal, South Africa, and has been identified in neighbouring provinces and countries. Since no commercially grown hybrids have been identified to be resistant to the disease, a study was initiated to assess the susceptibility of hybrids to the pathogen. The objective of the study was to identify high-yielding hybrids that were least susceptible to grey leaf spot, and to identify hybrids best suited to stubble and conventionally ploughed tillage systems. Linear regression of relative yield against relative disease severity identified high-yielding maize hybrids, including PAN 6480, that were least susceptible, SNK 2888, was tolerant, whilst PAN 6528 was most susceptible to disease. The susceptibility of hybrids to grey leaf spot was affected similarly by stubble and conventional tillage practices over the seasons of the study. In the 1993/94 season with adequate rainfall and favourable for ...