Time filter

Source Type

Onaga G.,International Rice Research Institute | Onaga G.,National Crops Resources Research Institute NaCRRI | Drame K.N.,Africa Rice Center | Ismail A.M.,International Rice Research Institute
Functional Plant Biology | Year: 2016

Iron nutrition in plants is highly regulated in order to supply amounts sufficient for optimal growth while preventing deleterious effects. In response to iron deficiency, plants induce either reduction-based or chelation-based mechanisms to enhance iron uptake from the soil. Major physiological traits and genes involved in these mechanisms have been fairly well described in model plants like Arabidopsis thaliana (L. Heynh.) and rice (Oryza sativa L.). However, for rice, iron toxicity presents a major challenge worldwide and causes yield reductions because rice is widely cultivated in flooded soils. Nonetheless, rice employs different mechanisms of adaptation to iron-toxicity, which range from avoidance to tissue tolerance. The physiological and molecular bases of such mechanisms have not been fully investigated and their use in breeding for iron-toxicity tolerance remains limited. Efforts to precisely characterise iron-toxicity control mechanisms may help speed-up the development of tolerant rice varieties. Considering how far the understanding of iron dynamics in the soil and plants has progressed, we consider it valuable to exploit such knowledge to improve rice tolerance to iron toxicity. Here we present the mechanisms that regulate iron uptake from the rhizosphere to the plant tissues together with the possible regulators involved. In addition, a genetic model for iron-toxicity tolerance in rice, which hypothesises possible modulation of key genes involved in iron nutrition and regulation is presented. The possibility of incorporating such relevant regulators in breeding is also discussed.


Ceballos H.,Aereo | Kawuki R.S.,National Crops Resources Research Institute NaCRRI | Gracen V.E.,Cornell University | Yencho G.C.,North Carolina State University | Hershey C.H.,Aereo
Theoretical and Applied Genetics | Year: 2015

Key message: Consolidates relevant molecular and phenotypic information on cassava to demonstrate relevance of heterosis, and alternatives to exploit it by integrating different tools. Ideas are useful to other asexually reproduced crops. Abstract: Asexually propagated crops offer the advantage that all genetic effects can be exploited in farmers’ production fields. However, non-additive effects complicate selection because, while influencing the performance of the materials under evaluation, they cannot be transmitted efficiently to the following cycle of selection. Cassava can be used as a model crop for asexually propagated crops because of its diploid nature and the absence of (known) incompatibility effects. New technologies such as genomic selection (GS), use of inbred progenitors based on doubled haploids and induction of flowering can be employed for accelerating genetic gains in cassava. Available information suggests that heterosis, non-additive genetic effects and within-family variation are relatively large for complex traits such as fresh root yield, moderate for dry matter or starch content in the roots, and low for defensive traits (pest and disease resistance) and plant architecture. The present article considers the potential impact of different technologies for maximizing gains for key traits in cassava, and highlights the advantages of integrating them. Exploiting heterosis would be optimized through the implementation of reciprocal recurrent selection. The advantages of using inbred progenitors would allow shifting the current cassava phenotypic recurrent selection method into line improvement, which in turn would allow designing outstanding hybrids rather than finding them by trial and error. © 2015, The Author(s).


Studholme D.J.,University of Exeter | Wasukira A.,University of Exeter | Wasukira A.,National Crops Resources Research Institute NaCRRI | Paszkiewicz K.,University of Exeter | And 5 more authors.
Genes | Year: 2011

We present draft genome sequences for three strains of Xanthomonas species, each of which was associated with banana plants (Musa species) but is not closely related to the previously sequenced banana-pathogen Xanthomonas campestris pathovar musacearum. Strain NCPPB4393 had been deposited as Xanthomonas campestris pathovar musacearum but in fact falls within the species Xanthomonas sacchari. Strain NCPPB1132 is more distantly rel ted to Xanthomonas sacchari whilst strain NCPPB 1131 grouped in a distinct species-level clade related to X. sacchari, along with strains from ginger, rice, cotton and sugarcane. These three newly sequenced strains share many genomic features with the previously sequenced Xanthomonas albilineans, for example possessing an unsual metE allele and lacking the Hrp type III secretion system. However, they are distinct from Xanthomonas albilineans in many respects, for example showing little evidence of genome reduction. They also lack the SPI-1 type III secretion system found in Xanthomonas albilineans. Unlike X. albilineans, all three strains possess a gum gene cluster. The data reported here provide the first genome-wide survey of non-Hrp Xanthomonas species other than Xanthomonas albilineans, which is an atypical member of this group. We hope that the availability of complete sequence data for this group of organisms is the first step towards understanding their interactions with plants and identifying potential virulence factors. © 2011 by the authors; licensee MDPI, Basel, Switzerland.


PubMed | University of Exeter, National Crops Resources Research Institute NaCRRI and UK Environment Agency
Type: Published Erratum | Journal: Genes | Year: 2016

Following publication of our article [1], we found errors in analyses performed by the corresponding author (DJS) related to the phylogenetic relationship between Xylella species and the other xanthomonads. These errors do not make any difference to the main findings and conclusions reported in our paper. For example, the phylogenetic positions of NCPPB1131, NCPPB1132 and NCPPB4393 within the Group 1 Xanthomonas species are unaffected. However, we wish to apologize to the authors of a previous work [2] for creating any negative impression on the quality of their phylogenetic analyses and to take this opportunity to rectify the errors. [...].


Sseruwu G.,University of KwaZulu - Natal | Sseruwu G.,Mukono Zonal Agricultural Research and Development Institute MUZARDI | Shanahan P.,University of KwaZulu - Natal | Melis R.,University of KwaZulu - Natal | Ssemakula G.,National Crops Resources Research Institute NaCRRI
Euphytica | Year: 2016

Alternaria blight (Alternaria spp.) is an important sweetpotato disease in Uganda causing yield losses of over 50 % in susceptible genotypes. In Uganda, Alternaria bataticola and Alternaria alternata are the major species with A. bataticola the more aggressive of the two. The most effective control measure for this disease is the use of resistant genotypes. This study was conducted to determine the inheritance of resistance to Alternaria blight and the general and specific combining abilities of the available germplasm. Sixteen parental clones varying in reaction to Alternaria blight were crossed using the North Carolina II mating scheme. Due to incompatibility of some parents, two sets of compatible parents were formed. Differences among the families for Alternaria blight severity were significant while general combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant (P < 0.001) for the disease with GCA sum of squares (SS) being more predominant at 67.4 % of the treatment SS for Set 1 and the SCA SS predominant at 54.0 % of the treatment SS for Set 2. This indicated that both additive and non-additive effects are important in controlling this trait. Some parents with high, negative GCA effects produced families with undesirable SCA effects and the reverse was also true. This implies that the best parents should not be chosen on GCA alone but also on SCA of their best crosses. The wide range in the area under disease progress curve for the families indicated that it was possible to select for highly resistant genotypes. © 2016 Springer Science+Business Media Dordrecht


Ochola D.,National Crops Resources Research Institute NaCRRI | Ochola D.,Makerere University | Tusiime G.,Makerere University
Asian Journal of Plant Pathology | Year: 2011

In the present study, we assessed the pathogenicity of the prevalent strains of Rice Yellow Mottle Virus (RYMV) present in Eastern Uganda and identified suitable donors for durable resistance among rice cultivars. Screenhouse studies were conducted using eight isolates of the virus against 16 rice cultivars. Isolate aggressiveness and cultivar resistance were assessed in terms of disease severity and percentage stunting following mechanical inoculation by the finger-rub technique. Highly significant differences (p<0.001) between rice cultivars for both parameters revealed the occurrence of different genetic factors for resistance among the rice cultivars. Mean disease severity and percentage stunting ranged between 0.9-9.0 and -1.1-32.4%, respectively for individual cultivars. The absence of significant isolate-by-cultivar interaction suggests a race-non-specific resistance. No significant differences in aggressiveness were obtained between isolates, indicating limited pathotype diversity in Eastern Uganda as evidenced by the absence of mega-environments among the prevalent strains. Based on cultivar resistance ranking, three O. sativa subspecies japonica (NERICA6, ITA257 and ITA325) and two O. sativa subspecies indica (WAC116 and WAC117) were identified as the potential sources of resistance for improving susceptible local varieties. The confirmed resistance breakdown in GIGANTE has important implications for plant breeding and disease control strategies. Therefore, pyramiding different sources of resistance is recommended for enhanced durability of resistance. In addition, the use of sufficient prerelease challenge by the combination of isolates with different levels of aggressiveness will delay the rise of susceptibility in deployed resistant cultivars. © 2011 Academic Journals Inc.


Nuwamanya E.,National Crops Resources Research Institute NaCRRI | Baguma Y.,National Crops Resources Research Institute NaCRRI | Wembabazi E.,National Crops Resources Research Institute NaCRRI | Rubaihayo P.,Makerere University
African Journal of Biotechnology | Year: 2011

Some properties of starches from cassava, potato and sweet potato were compared with cereal starches from maize, wheat, millet and sorghum. The aim was to determine the properties of tuber and root crop starches and compare them with cereal starches in addition to unravelling the potential of commonly grown sorghum and millet climate resilient crops as cheap and sustainable sources of starch. Significant variations were observed for amylose content and solution properties of starches, where blue values for amylose ranged from 0.355 in potato to 0.476 in cassava, but were averagely low in cereal starches. Amylose leaching increased with temperature with the highest value (0.432) in cassava at 80°C compared with cereal starches (average 0.361). Starch amylosis increased with time of hydrolysis and was highest (>16%) for millet and sorghum and least for potato (<8.5% average). Average swelling power at 80°C was high for cassava (8.58 g/g) and potato (8.44 g/g) compared with sweet potato (6.88 g/g) and low among cereal starches (5.17 g/g). Similarly, starch solubility was low in potato (0.77 g/g) and sweet potato (0.577 g/g) compared with cassava (1.23 g/g). The paste clarity was also high for cassava (48.32%) and potato (42.16%) and least for sweet potato derived starches (23.22%) and all the cereal starches (14.97%). These properties demonstrate the untapped potential of cassava and tuber based starches for use in food and non-food applications previously dominated by cereal starches. © 2011 Academic Journals.


Nuwamanya E.,National Crops Resources Research Institute NaCRRI | Chiwona-Karltun L.,Swedish University of Agricultural Sciences | Kawuki R.S.,National Crops Resources Research Institute NaCRRI | Baguma Y.,National Crops Resources Research Institute NaCRRI
Ambio | Year: 2012

Global climate issues and a looming energy crisis put agriculture under pressure in Sub-Saharan Africa. Climate adaptation measures must entail sustainable development benefits, and growing crops for food as well as energy may be a solution, removing people from hunger and poverty without compromising the environment. The present study investigated the feasibility of using non-food parts of cassava for energy production and the promising results revealed that at least 28% of peels and stems comprise dry matter, and 10 g feedstock yields >8.5 g sugar, which in turn produced >60% ethanol, with pH = 2.85, 74-84% light transmittance and a conductivity of 368 mV, indicating a potential use of cassava feedstock for ethanol production. Thus, harnessing cassava for food as well as ethanol production is deemed feasible. Such a system would, however, require supportive policies to acquire a balance between food security and fuel. © Royal Swedish Academy of Sciences 2011.


Mwanga R.O.M.,North Carolina State University | Mwanga R.O.M.,National Crops Resources Research Institute NaCRRI | Yencho G.C.,214A Kilgore Hall | Gibson R.W.,University of Greenwich | Moyer J.W.,North Carolina State University
Plant Disease | Year: 2013

Evaluating sweetpotato (Ipomoea batatas) genotypes for resistance to sweetpotato virus disease (SPVD) has been slow and inefficient. Ipomoea setosa plants, normally used as the source of scions for graftinfecting sweetpotatoes with viral diseases, are often severely stunted and their mortality is 10 to 30% when infected with SPVD, making them unsuitable as scions. Tanzania, a landrace of I. batatas widely grown in East Africa, was found to be a superior host for maintaining and increasing SPVD inoculum (scions) for mass grafting. Modifications to a cleft-grafting technique also increased survival of grafted SPVD-affected scions from 5 to 100%. These modifications, coupled with an efficient SPVD scoring technique, allowed rapid screening of large sweetpotato populations for SPVD resistance. Plant recovery from SPVD is reported here as a component of SPVD resistance. Differences in recovery from SPVD were detected among progenies, indicating its genetic basis. Plant tip dieback, a hypersensitivity response, was observed only in families with cv. Wagabolige as a parent. These findings may open up new opportunities for improved understanding and control of this devastating disease. © 2013 The American Phytopathological Society.


GIBSON R.W.,Chatham University | MPEMBE I.,National Crops Resources Research Institute NaCRRI | MWANGA R.O.M.,National Crops Resources Research Institute NaCRRI
Journal of Agricultural Science | Year: 2011

SUMMARYNASPOT 11 is a recently released sweet potato cultivar, bred by participatory plant breeding (PPB) in Uganda. It is already grown extensively by farmers who call it Tomulabula. In on-farm and on-station yield trials, Tomulabula yielded as well as the researcher-bred variety NASPOT 1 and sometimes more than the local landraces Dimbuka and New Kawogo, which have also been released. Farmers were asked to what extent Tomulabula, NASPOT 1 (the most popular station-bred cultivar in Uganda) and the local indigenously bred cultivar they were currently growing satisfied 52 attributes previously identified by farmers as beneficial in sweet potato. Those cultivars whose breeding involved farmers (Tomulabula and the local cultivar) were perceived mostly to satisfy a broad range of attributes (i.e. had few 'Very Bad' scores) while those which involved researchers (Tomulabula and NASPOT 1) were the most frequently rated as 'Very Good' for specific attributes. Instances were observed and accounts given of how Tomulabula is sold at a premium and how it had improved farmers' lives. These outcomes are attributed to PPB combining the strengths of farmers and researchers. The involvement of the Ugandan National Sweetpotato Program (UNSP) ensures that planting material will be conserved and also available in adequate amounts for official distribution.

Loading National Crops Resources Research Institute NaCRRI collaborators
Loading National Crops Resources Research Institute NaCRRI collaborators