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Obidiegwu J.E.,Max Planck Institute for Plant Breeding Research | Obidiegwu J.E.,National Root Crops Research Institute Umudike | Flath K.,Julius Kuhn Institute | Gebhardt C.,Max Planck Institute for Plant Breeding Research
Theoretical and Applied Genetics | Year: 2014

Key message: Identification of resistance genes to potato wart disease caused by Synchytrium endobioticum is the key for developing diagnostic markers for breeding resistant cultivars. We present an overview on the current knowledge of this host-pathogen system and molecular advances while highlighting future research focus. Potato wart is a quarantined disease of cultivated potato (Solanum tuberosum L.) caused by the obligate biotrophic, soil-borne fungus Synchytrium endobioticum (Schilb.) Perc. Since its discovery by Schilberszky in 1896, the management of wart disease was enabled by research efforts focusing on understanding and classifying the causative agent, its mode of infection, pathogenesis, geographical distribution, detection and chemical control, on developing screening methods for host resistance and on genetic analyses, which led to the development of resistant cultivars. These early successes are currently challenged by new S. endobioticum pathotypes evolving and the increased risk of dissemination by potato tuber trade. New research efforts are therefore required to ensure continuation of effective and sustainable management of the potato wart disease. Advances in molecular biology and genomic tools offer potential for innovations. This review presents an overview on what we know about this complex host-pathogen interaction, highlights recent molecular work and embarks on an outlook towards future research directions. © 2014 The Author(s).

Obidiegwu J.E.,Max Planck Institute for Plant Breeding Research | Obidiegwu J.E.,National Root Crops Research Institute Umudike | Sanetomo R.,Max Planck Institute for Plant Breeding Research | Sanetomo R.,Obihiro University of Agriculture and Veterinary Medicine | And 6 more authors.
BMC Genetics | Year: 2015

Background: The soil borne, obligate biotrophic fungus Synchytrium endobioticum causes tumor-like tissue proliferation (wart) in potato tubers and thereby considerable crop damage. Chemical control is not effective and unfriendly to the environment. S. endobioticum is therefore a quarantined pathogen. The emergence of new pathotypes of the fungus aggravate this agricultural problem. The best control of wart disease is the cultivation of resistant varieties. Phenotypic screening for resistant cultivars is however time, labor and material intensive. Breeding for resistance would therefore greatly benefit from diagnostic DNA markers that can be applied early in the breeding cycle. The prerequisite for the development of diagnostic DNA markers is the genetic dissection of the factors that control resistance to S. endobioticum in various genetic backgrounds of potato. Results: Progeny of a cross between a wart resistant and a susceptible tetraploid breeding clone was evaluated for resistance to S. endobioticum pathotypes 1, 2, 6 and 18 most relevant in Europe. The same progeny was genotyped with 195 microsatellite and 8303 single nucleotide polymorphism (SNP) markers. Linkage analysis identified the multi-allelic locus Sen1/RSe-XIa on potato chromosome XI as major factor for resistance to all four S. endobioticum pathotypes. Six additional, independent modifier loci had smaller effects on wart resistance. Combinations of markers linked to Sen1/RSe-XIa resistance alleles with one to two additional markers were sufficient for obtaining high levels of resistance to S. endobioticum pathotypes 1, 2, 6 and 18 in the analyzed genetic background. Conclusions: Potato resistance to S. endobioticum is oligogenic with one major and several minor resistance loci. It is composed of multiple alleles for resistance and susceptibility that originate from multiple sources. The genetics of resistance to S. endobioticum varies therefore between different genetic backgrounds. The DNA markers described in this paper are the starting point for pedigree based selection of cultivars with high levels of resistance to S. endobioticum pathotypes 1, 2, 6 and 18. © 2015 Obidiegwu et al.; licensee BioMed Central.

Obidiegwu J.E.,James Hutton Institute | Obidiegwu J.E.,National Root Crops Research Institute Umudike | Bryan G.J.,James Hutton Institute | Jones H.G.,University of Dundee | And 2 more authors.
Frontiers in Plant Science | Year: 2015

Potato (Solanum tuberosum L.) is often considered as a drought sensitive crop and its sustainable production is threatened due to frequent drought episodes. There has been much research aiming to understand the physiological, biochemical, and genetic basis of drought tolerance in potato as a basis for improving production under drought conditions. The complex phenotypic response of potato plants to drought is conditioned by the interactive effects of the plant's genotypic potential, developmental stage, and environment. Effective crop improvement for drought tolerance will require the pyramiding of many disparate characters, with different combinations being appropriate for different growing environments. An understanding of the interaction between below ground water uptake by the roots and above ground water loss from the shoot system is essential. The development of high throughput precision phenotyping platforms is providing an exciting new tool for precision screening, which, with the incorporation of innovative screening strategies, can aid the selection and pyramiding of drought-related genes appropriate for specific environments. Outcomes from genomics, proteomics, metabolomics, and bioengineering advances will undoubtedly compliment conventional breeding strategies and presents an alternative route toward development of drought tolerant potatoes. This review presents an overview of past research activity, highlighting recent advances with examples from other crops and suggesting future research directions. © 2015 Obidiegwu, Bryan, Jones and Prashar.

Amadi C.O.,National Root Crops Research Institute Umudike | Onyeka J.,National Root Crops Research Institute Umudike | Chukwu G.O.,Michael Okpara University of Agriculture | Okoye B.C.,National Root Crops Research Institute Umudike
Journal of Crop Improvement | Year: 2015

Declining yields of local taro cultivars, worsened in recent years by outbreak of taro leaf blight (TLB), necessitate the development of varieties that combine TLB resistance with high yield and quality. The objective of the experiment was to obtain viable true taro seeds (TTS), the lack of which has hindered local breeding effort to improve taro. Fifteen exotic cultivars of taro, obtained from International Network on Edible Aroids (INEA) as part of an EU-funded project on “Adapting Clonally Propagated Crops to Climatic and Commercial Change,” and four local cultivars constituted the crossing block at Umudike (5°24′ to 5°30′ N; 7°31ʹ to 7°37ʹE) in south eastern Nigeria in 2013. One hundred and nine crosses were made, of which 18.3% were successful, but only infructescence from nine crosses developed to maturity and produced seeds. Germination of these TTS started on the 7th day after sowing. Seedlings that developed from these seeds were transplanted into small bags filled with sterilized peat mixed with vermiculite. Each plant is expected to be genetically different from all others and could be a potentially improved cultivar. This is the first report of successful hybridization, production of TTS, and development of seedlings from true seed of taro in Nigeria. © , Copyright © Taylor & Francis Group, LLC.

Njoku D.N.,National Root Crops Research Institute Umudike | Afuape S.O.,National Root Crops Research Institute Umudike | Ebeniro C.N.,National Root Crops Research Institute Umudike
African Journal of Agricultural Research | Year: 2010

The use of some leguminous crops for soil fertility improvement is being promoted for root and tuber crops production in Nigeria. Cowpea has a lot of advantages and is more compatible with cassava than other legumes. Cowpea (Vigna unguiculata) was intercropped with cassava (NR 8082 at 10,000 plants per hectare) at four plant densities (20,000; 40,000; 60,000 and 80,000 plants per hectare) in 2004 and 2005 planting seasons at the National Root Crops Research Institute (NRCRI) research farm in Umudike (07° 33 ' E, 05° 29 ' N), Southeastern Nigeria. The experiment was arranged in a randomized complete block design (RCBD) with three replications. The leaf area index (LAI) of cassava was highest with the highest cowpea planting density in 2005, but not in 2004 planting year. Similarly, maximum fresh root yield (t/ha) of cassava was influenced by population density in 2005, but not in 2004 planting year. Cassava root yield was highest with the cowpea planting density of 80,000 plants/ha. Cowpea variety IT93K- 452-1 at a population density of 80, 000 plants/ha is recommended for increased soil fertility for cassava production in the Southeastern Nigeria. © 2010 Academic Journals.

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