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Tolmay V.L.,Agricultural Research Council Small Grain Institute | Sydenham S.L.,Agricultural Research Council Small Grain Institute | Boshoff W.H.P.,Agricultural Research Council Small Grain Institute | Boshoff W.H.P.,Pannar Seed Pty Ltd. | And 3 more authors.
Journal of Plant Registrations | Year: 2016

Russian wheat aphid (RWA; Diuraphis noxia Kurdjumov) and wheat rusts (stem rust [caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.], leaf rust [caused by Puccinia triticina Eriks.], and stripe rust [caused by Puccinia striiformis Westend. f. sp. tritici Eriks.]) are major constraints to wheat (Triticum aestivum L.) production. We aimed to combine resistance to these four biotic constraints in ‘Kariega’, a South African spring wheat cultivar. Five spring wheat lines, SA16486 (Reg. No. GP-990, PI 674173), SA16487 (Reg. No. GP-991, PI 674174), SA16488 (Reg. No. GP-992, PI 674175), SA16490 (Reg. No. GP-993, PI 674176), and SA16491 (Reg. No. GP-994, PI 674177) were developed by the Agricultural Research Council-Small Grain Institute, South Africa, and released in 2015. These F3:6 lines are descended from a topcross made in 2001 between two backcrossed lines, one with RWA resistance from PI 225227 (resistant to biotypes RWASA1, RWASA2, and RWASA3) and another with Sr35 (resistant to the Ug99 race group). Phenotypic screening for RWA resistance (using biotype RWASA1) and marker assisted selection for rust resistance genes including Sr35, Lr34/Yr18/Sr57/Pm38/Sb1/ Ltn1, and QYr.sgi-2B.1 were used to identify the targeted traits during selection. The unique combination of aphid and rust resistance, medium to high yield potential, and good end-use quality makes these wheat lines useful for wheat breeders with an interest in these resistance traits. © 2015 Crop Science Society of America. All rights reserved. Source


Berger D.K.,University of Pretoria | Carstens M.,University of Pretoria | Korsman J.N.,University of Pretoria | Middleton F.,Pannar Seed Pty Ltd. | And 3 more authors.
BMC Genetics | Year: 2014

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. © 2014 Berger et al.; licensee BioMed Central Ltd. Source


Korsman J.,University of Pretoria | Meisel B.,University of Pretoria | Meisel B.,Monsanto Corporation | Kloppers F.J.,Pannar Seed Pty Ltd. | And 2 more authors.
European Journal of Plant Pathology | Year: 2012

Grey leaf spot is an important maize foliar disease caused by the fungal pathogens Cercospora zeae-maydis and Cercospora zeina. Although methods exist to detect these Cercospora species in maize, current techniques do not allow quantification of the fungi in planta. We developed a real-time SYBR® Green PCR assay for quantification of grey leaf spot disease in maize based on the amplification of a fragment of a cytochrome P450 reductase (cpr1) gene. In planta fungal DNA content was normalised to a maize glutathione S-transferase III gene (gst3) to yield values of ng Cercospora DNA/mg maize DNA. The assay was specific to the two Cercospora spp., and we observed no amplification of the cpr1 fragment in non-target maize leaf pathogens or saprophytes. The assay was employed to quantify C. zeina in glasshouse inoculated maize plants and grey leaf spot infected field plants of resistant and susceptible maize lines. In both instances, C. zeina DNA content correlated with symptomatic leaf lesion area, and the susceptible maize line contained significantly more C. zeina DNA than the resistant line. Sequence differences between the C. zeina and C. zeae-maydis cpr1 amplicons enabled us to perform melt curve analyses to identify the Cercospora species causing grey leaf spot at a particular location. This assay has application in the early detection and quantification of Cercospora spp., both of which are important tools in grey leaf spot disease management and maize breeding programmes. © 2011 The Author(s). Source

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