Open Access Highly Accessed Research article

Mapping QTL conferring resistance in maize to gray leaf spot disease caused by Cercospora zeina

Dave K Berger1*, Maryke Carstens1, Jeanne N Korsman1, Felix Middleton2, Frederik J Kloppers2, Pangirayi Tongoona3 and Alexander A Myburg4

Author Affiliations

1 Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), Plant Sciences Complex, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa

2 PANNAR SEED (Pty) Ltd, PO Box 19, Greytown, South Africa

3 African Centre for Crop Improvement, University of KwaZulu-Natal, Pietermaritzburg, South Africa

4 Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa

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BMC Genetics 2014, 15:60  doi:10.1186/1471-2156-15-60

Published: 22 May 2014

Abstract

Background

Gray leaf spot (GLS) is a globally important foliar disease of maize. Cercospora zeina, one of the two fungal species that cause the disease, is prevalent in southern Africa, China, Brazil and the eastern corn belt of the USA. Identification of QTL for GLS resistance in subtropical germplasm is important to support breeding programmes in developing countries where C. zeina limits production of this staple food crop.

Results

A maize RIL population (F7:S6) from a cross between CML444 and SC Malawi was field-tested under GLS disease pressure at five field sites over three seasons in KwaZulu-Natal, South Africa. Thirty QTL identified from eleven field trials (environments) were consolidated to seven QTL for GLS resistance based on their expression in at least two environments and location in the same core maize bins. Four GLS resistance alleles were derived from the more resistant parent CML444 (bin 1.10, 4.08, 9.04/9.05, 10.06/10.07), whereas the remainder were from SC Malawi (bin 6.06/6.07, 7.02/7.03, 9.06). QTLs in bin 4.08 and bin 6.06/6.07 were also detected as joint QTLs, each explained more than 11% of the phenotypic variation, and were identified in four and seven environments, respectively. Common markers were used to allocate GLS QTL from eleven previous studies to bins on the IBM2005 map, and GLS QTL “hotspots” were noted. Bin 4.08 and 7.02/7.03 GLS QTL from this study overlapped with hotspots, whereas the bin 6.06/6.07 and bin 9.06 QTLs appeared to be unique. QTL for flowering time (bin 1.07, 4.09) in this population did not correspond to QTL for GLS resistance.

Conclusions

QTL mapping of a RIL population from the subtropical maize parents CML444 and SC Malawi identified seven QTL for resistance to gray leaf spot disease caused by C. zeina. These QTL together with QTL from eleven studies were allocated to bins on the IBM2005 map to provide a basis for comparison. Hotspots of GLS QTL were identified on chromosomes one, two, four, five and seven, with QTL in the current study overlapping with two of these. Two QTL from this study did not overlap with previously reported QTL.

Keywords:
Gray leaf spot; Grey leaf spot; GLS; Cercospora; QTL; Maize; Corn