High genetic diversity of the grey leaf spot pathogen, Cercospora zeina, observed in commercial maize in South Africa
D. BERGER (1), M. Muller (2), N. Kunene (1), B. Crampton (2), B. Bluhm (3), S. Phillips (1), I. Barnes (4) (1) Plant Science Department, Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa; (2) Plant Science Department, Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa; (3) Department of Plant Pathology, University of Arkansas, U.S.A.; (4) Genetics Department, Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa

Grey leaf spot (GLS) of maize is a foliar disease of increasing importance globally. This is mainly due to the adoption of conservation tillage that facilitates over-wintering of the disease-causing pathogen on debris. Two Dothidiomycete species, Cercospora zeae-maydis and Cercospora zeina, cause GLS. The latter species is associated with GLS in Africa. The incidence and severity of GLS has been steadily increasing in South Africa. Knowledge of the population genetics and reproductive strategy of the pathogen is important for sustainable control strategies. A collection of more than 350 single spore isolates was made from GLS lesions from commercial maize grown in three regions (KwaZulu-Natal, Mpumalanga and North West Province) of South Africa. All isolates were identified as C. zeina using a histone H3 PCR diagnostic test. C. zeae-maydis was not found. Fourteen microsatellite markers were designed from C. zeina draft genome sequence information, and produced an average of five alleles per marker across the isolates. More than 240 multi-locus haplotypes were identified with a gene diversity across the regions of 0.35. No regional population structure was observed and gene flow between regions was high (Nm=5.51). Mating type gene analysis revealed that each isolate had either MAT1-1-1 or MAT1-2-1, and that both idiomorphs were found in all three regions. MAT gene ratios indicated evidence for sexual recombination, although the sexual stage of the fungus has not been observed, as is the case for many Cercospora spp. The results revealed significant movement of the pathogen between maize growing regions of South Africa, and evidence for both asexual and sexual reproduction. The knowledge gained in this study is valuable for implementation of disease control strategies against GLS in South Africa.

Abstract Number: P13-408
Session Type: Poster