KARI Agricultural Research Centre Muguga South Annual Report 2007

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Kenya Agricultural Research Institute
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Gray leaf spot of corn caused by Cercospora zeae-maydis has increased in incidence and severity due to the wide-spread use of conservation tillage in conjunction with the susceptibility of most commercially grown hybrids. Though gray leaf spot was first identified in 1925 from lesions on corn leaves collected near McClure, in Alexander County, Illinois, the disease did not become a problem until the mid-1970s. This disease is a significant threat where corn is grown continously Tillage practices can reduce levels of inoculum and although rotation is a key management practice, susceptibility to gray leaf spot should be carefully considered when selecting a hybrid. Host resistance is an ideal and promising approach to disease control. Hybrids exhibit differing levels of partial resistance to gray leaf spot. Gray leaf spot will still develop on a partially resistant hybrid, but it typically is slower to develop and less severe (Vincelli, 2001). Verma 2001 reported yield losses due to GLS as ranging from 28 to 54% with an average loss of 33.5%. In the same studies, both GCA and SCA were found highly significant for GLS indicating the importance of both additive and non-additive components although GLS was relatively more important.