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Pretorius Z.A.,University of the Free State | Visser B.,University of the Free State | Terefe T.,Agriculture Research Council Small Grain Institute | Herselman L.,University of the Free State | And 7 more authors.
Australasian Plant Pathology | Year: 2015

To identify races of Puccinia triticina in southern Africa, samples of infected wheat leaves obtained from Zimbabwe, Zambia and Malawi were analysed at the University of the Free State, Bloemfontein and the Agricultural Research Council-Small Grain Institute, Bethlehem, South Africa (SA). Four races were identified from 63 isolates obtained during 2011–2013. Using the North American notation, these races coded to MCDS (74.6 %), TCPS (12.7 %), FBPT (6.3 %) and SCDS (6.3 %). MCDS and TCPS occurred in both Zimbabwe and Zambia whereas FBPT and SCDS were only detected in Zimbabwe and Malawi, respectively. Three of these races (MCDS, FPBT and SCDS) are also known in SA. SSR analysis of races detected in southern Africa suggested that MCDS and FPBT are more closely related to CCPS (3SA45), a race identified in SA in 2009. Occurrence of similar races across southern Africa indicates migration of inoculum between countries, and highlights the need for each country to monitor and share information on virulence changes in the region. In seedling tests, over 72 % of Zimbabwean commercial cultivars were susceptible to race TCPS which occurred in both Zimbabwe and Zambia. To predict occurrence of adult plant resistance (APR) in these cultivars, they were tested for the presence of gene Lr34 which confers durable resistance to multiple fungal pathogens. Only three cultivars were positive for this gene suggesting that most of the current Zimbabwean commercial cultivars may be susceptible to leaf rust both as seedlings and adult plants, assuming the absence of other APR genes. Three cultivars and 15 breeding lines, all highly resistant as seedlings across races, carried Lr19. One line contained Lr19 and Lr34. It is suggested that sources of race non-specific resistance genes be included in wheat breeding programs in Zimbabwe. © 2014, Australasian Plant Pathology Society Inc. Source

Mubayiwa M.,University of Zimbabwe | Mutasa W.,Crop Breeding Institute | Gasura E.,University of Zimbabwe | Mabasa S.,University of Zimbabwe
South African Journal of Botany | Year: 2016

In sub-tropics, most sweetpotato genotypes do not flower at all. The aim of this study was to develop methods of inducing flowering based on the application of 2.4-dichlorophenoxyacetic acid (2.4D) and grafting of non-flowering genotypes on rootstocks of genotypes that flower. The first experiment was a 3 * 4 * 2 factorial experiment repeated in summer and winter seasons. Four levels of 2.4D (0, 40, 80 and 120 ppm) were applied at two levels (once and twice) on three sweetpotato genotypes. The second experiment involved grafting scions of two genotypes on rootstocks of flowering genotype. During summer season there were significant differences (P < 0.05) in bud and flower counts among genotypes, concentration and number of split applications but non-significant differences on all the interactions. Genotype 1 produced more buds and flowers followed by genotype 3 and 2. The highest numbers of buds and flowers were observed at 40 ppm and 80 ppm. At higher concentrations (80 and 120 ppm), the physiological disorders including leaf epinasty, shoot die back and stem cracking were extensive. The optimum concentration for 2.4D proved to be 40 ppm and could induce flowering with less physiological disorders. Split application resulted in bud death and delayed flowering. Results showed that grafting has a genotype dependent effect on flowering. Genotype 3 managed to flower but genotype 2 did not flower at all when their scions were grafted on the flowering rootstocks of genotype 1. © 2016 South African Association of Botanists Source

Cortes A.J.,Uppsala University | Fernandez A.C.,U.S. Department of Agriculture | Soler T.,International Center for Tropical Agriculture Bean Project | Franco-Herrera N.,International Center for Tropical Agriculture Bean Project | And 2 more authors.
BMC Genetics | Year: 2012

Background: In common bean, expressed sequence tags (ESTs) are an underestimated source of gene-based markers such as insertion-deletions (Indels) or single-nucleotide polymorphisms (SNPs). However, due to the nature of these conserved sequences, detection of markers is difficult and portrays low levels of polymorphism. Therefore, development of intron-spanning EST-SNP markers can be a valuable resource for genetic experiments such as genetic mapping and association studies.Results: In this study, a total of 313 new gene-based markers were developed at target genes. Intronic variation was deeply explored in order to capture more polymorphism. Introns were putatively identified after comparing the common bean ESTs with the soybean genome, and the primers were designed over intron-flanking regions. The intronic regions were evaluated for parental polymorphisms using the single strand conformational polymorphism (SSCP) technique and Sequenom MassARRAY system. A total of 53 new marker loci were placed on an integrated molecular map in the DOR364 × G19833 recombinant inbred line (RIL) population. The new linkage map was used to build a consensus map, merging the linkage maps of the BAT93 × JALO EEP558 and DOR364 × BAT477 populations. A total of 1,060 markers were mapped, with a total map length of 2,041 cM across 11 linkage groups. As a second application of the generated resource, a diversity panel with 93 genotypes was evaluated with 173 SNP markers using the MassARRAY-platform and KASPar technology. These results were coupled with previous SSR evaluations and drought tolerance assays carried out on the same individuals. This agglomerative dataset was examined, in order to discover marker-trait associations, using general linear model (GLM) and mixed linear model (MLM). Some significant associations with yield components were identified, and were consistent with previous findings.Conclusions: In short, this study illustrates the power of intron-based markers for linkage and association mapping in common bean. The utility of these markers is discussed in relation with the usefulness of microsatellites, the molecular markers by excellence in this crop. © 2012 Galeano et al.; licensee BioMed Central Ltd. Source

Hirakawa H.,Kazusa DNA Research Institute | Shirasawa K.,Kazusa DNA Research Institute | Kosugi S.,Kazusa DNA Research Institute | Tashiro K.,Kyushu University | And 21 more authors.
DNA Research | Year: 2014

Cultivated strawberry (Fragaria x ananassa) is octoploid and shows allogamous behaviour. The present study aims at dissecting this octoploid genome through comparison with its wild relatives, F. iinumae, F. nipponica, F. nubicola, and F. orientalis by de novo whole-genome sequencing on an Illumina and Roche 454 platforms. The total length of the assembled Illumina genome sequences obtained was 698 Mb for F. x ananassa, and ∼200 Mb each for the four wild species. Subsequently, a virtual reference genome termed FANhybrid-r1.2 was constructed by integrating the sequences of the four homoeologous subgenomes of F. x ananassa, from which heterozygous regions in the Roche 454 and Illumina genome sequences were eliminated. The total length of FANhybrid-r1.2 thus created was 173.2 Mb with the N50 length of 5137 bp. The Illumina-assembled genome sequences of F. x ananassa and the four wild species were then mapped onto the reference genome, along with the previously published F. vesca genome sequence to establish the subgenomic structure of F. x ananassa. The strategy adopted in this study has turned out to be successful in dissecting the genome of octoploid F. x ananassa and appears promising when applied to the analysis of other polyploid plant species. © 2013 © The Author 2013. Published by Oxford University Press on behalf of Kazusa DNA Research Institute. Source

Ndhlela T.,Crop Breeding Institute | Herselman L.,University of the Free State | Magorokosho C.,CIMMYT Southern Africa Regional Office | Setimela P.,CIMMYT Southern Africa Regional Office | And 2 more authors.
Crop Science | Year: 2014

Maize (Zea mays) is the most important cereal crop in Zimbabwe and is grown by both large-and small-scale farmers who are located in different agro-ecological zones of the country. The development and dissemination of adapted and high-yielding maize cultivars to these agro-ecological zones involves conducting multi-environment trials (METs). This study was conducted with the objectives of i) understanding complex G × E interaction and stability of single cross hybrids generated using CIMMYT elite drought tolerant lines and Department of Research and Specialist Services (DR&SS) elite drought susceptible lines for grain yield across stress and nonstress environments and ii) to identify genotypes to recommend for further use in the breeding program. Initially, yield data of 80 maize single cross hybrids tested across seven environments during the 2009 to 2010 and 2010 to 2011 seasons were analyzed using the additive main effects and multiplicative interaction (AMMI) biplot method. The analysis was further done for 20 best performing genotypes to facilitate less congested graphical presentation. Combined analysis of variance showed highly significant differences for the G × E interaction, indicating the possibility of selection for stable genotypes. The five AMMI interaction principal component analyses (IPCAs; IPCA1, IPCA2, IPCA3, IPCA4, and IPCA5) explained 82.41% of the variation and they were highly significant. The results showed three genotypes with high yield performance and broad adaptability whilst narrow adaptations were also observed. Agricultural Research Trust Farm was the most powerful site in discriminating among genotypes and the most representative environment. © Crop Science Society of America. Source

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