National Crops Resources Research Institute

National Crops Resources Research Institute

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Wamatsembe I.M.,University of Adelaide | Asea G.,National Crops Resources Research Institute | Haefele S.M.,Rothamsted Research
Agronomy | Year: 2017

Maize production in Uganda is constrained by various factors, but especially drought and stem borers contribute to significant yield losses. Genetically modified (GM) maize with increased drought tolerance and/or Bt insect resistance (producing the Bacillus thuringiensis Cry protein) is considered as an option. For an ex ante impact analysis of these technologies, a farmer survey was carried out in nine districts of Uganda, representing the major farming systems. The results showed that farmers did rate stem borer and drought as the main constraints for maize farming. Most farmers indicated a positive attitude towards GM maize, and 86% of all farmers said they would grow GM maize. Farmer estimated yield losses to drought and stem borer damage were on average 54.7% and 23.5%, respectively, if stress occurred. Taking the stress frequency into consideration (67% for both), estimated yield losses were 36.5% and 15.6% for drought and stem borer, respectively. According to the ex-ante partial budget analysis, Bt hybrid maize could be profitable, with an average value/cost ratio of 2.1. Drought tolerant hybrid maize had lower returns and a value/cost ratio of 1.5. Negative returns occurred mainly for farmers with non-stressed grain yields below 2 t·ha-1. The regulatory framework in Uganda needs to be finalized with consideration of strengthening key institutions in the maize sector for sustainable introduction of GM maize. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.

McQuaid C.F.,Rothamsted Research | van den Bosch F.,Rothamsted Research | Szyniszewska A.,Rothamsted Research | Alicai T.,National Crops Resources Research Institute | And 3 more authors.
PLoS Computational Biology | Year: 2017

Trade or sharing that moves infectious planting material between farms can, for vertically-transmitted plant diseases, act as a significant force for dispersal of pathogens, particularly where the extent of material movement may be greater than that of infected vectors or inoculum. The network over which trade occurs will then effect dispersal, and is important to consider when attempting to control the disease. We consider the difference that planting material exchange can make to successful control of cassava brown streak disease, an important viral disease affecting one of Africa's staple crops. We use a mathematical model of smallholders’ fields to determine the effect of informal trade on both the spread of the pathogen and its control using clean-seed systems, determining aspects that could limit the damage caused by the disease. In particular, we identify the potentially detrimental effects of markets, and the benefits of a community-based approach to disease control. © 2017 McQuaid et al.

News Article | December 12, 2016

UKIRIGURU, TANZANIA--(Marketwired - December 12, 2016) - Tanzania recently became a partner of the Next Generation Cassava Breeding project (NextGen), joining Nigeria and Uganda in the global effort to improve cassava breeding in Africa. This partnership is expected to enhance the project's efforts to improve livelihoods for African cassava farmers. "Partnering with NextGen should help us develop tools to address biotic stresses like cassava brown streak disease, cassava mosaic disease, and cassava green mite, and improve cassava root yields that will serve to increase cassava production countrywide," said Heneriko Kulembeka, cassava breeder and NextGen coordinator in Tanzania. "The NextGen project will assist in determining good parental lines for different traits of interest." "Tanzania has one of the foremost cassava breeding programs in Africa," said Chiedozie Egesi, NextGen manager of the Cornell University-led project. "Because Tanzania shares African cassava germplasm, they will benefit from the genomic predictions that NextGen has already developed, use of the NextGen Cassavabase database and capacity for improved phenotyping." Cassava is a vital crop in Tanzania, second only to maize in volume produced. More than 80 percent of farmers in the country grow cassava, producing about 4.5 million tons of cassava roots annually. About three-quarters of the crop is used for human consumption. The rest is used for livestock feed and industrial purposes. A widely preferred and hardy staple, cassava is often stored in the ground and locally processed as a source of food in times of famine. Cassava farmers face many challenges raising their crop. Tanzania loses an estimated 2.5 million tons each year to cassava brown streak disease, cassava mosaic disease, and cassava green mite. There is poor access to improved planting materials and processing technologies, limited use of fertilizers and herbicides, and low investment in cassava research and improvement. To address these challenges, researchers in Tanzania's Ministry of Agriculture, Livestock, and Fisheries (DRD) will collaborate with scientists on the NextGen project largely through ongoing efforts at the Lake Zone Agricultural Research and Development Institute (LZARDI), the oldest agricultural research station in Tanzania. LZARDI scientists are well prepared to contribute to the efforts of NextGen partners through cassava-related research that includes breeding and improvement, molecular marker-assisted breeding for disease resistance, processing and product development, and agronomy studies. The NextGen Tanzania team consists of Kulembeka; Kiddo Mtunda, cassava breeder and coordinator (coastal Tanzania); Geoffrey Mkamilo, national team leader of the Cassava Research Program in Tanzania; Kasele Salum, assistant cassava breeder (Lake Zone); and Caroline Sichwale, assistant cassava breeder (Eastern Zone). NextGen is a global partnership led by International Programs in the College of Agriculture and Life Sciences at Cornell University, in collaboration with the International Institute of Tropical Agriculture and National Root Crops Research Institute breeding centers in Nigeria, the National Crops Resources Research Institute in Uganda, DRD in Tanzania, the West African Centre for Crop Improvement in Ghana, Makerere University in Uganda, and the Boyce Thompson Institute, USDA-ARS, and the U.S. Department of Energy in the United States. The Cornell-led project is funded by a $25 million, five-year grant from the Bill & Melinda Gates Foundation and the Department for International Development of the United Kingdom, and is in its fourth year.

Ogwok E.,National Crops Resources Research Institute | Ogwok E.,University of Witwatersrand | Ogwok E.,Donald Danforth Plant Science Center | Alicai T.,National Crops Resources Research Institute | And 3 more authors.
Plant Pathology | Year: 2015

Cassava brown streak disease (CBSD), caused by Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), ranks among the top seven biological threats to global food security. The disease poses a significant threat to cassava production in East and Central Africa (ECA). In Uganda, overall CBSD incidence increased by c. 20% since it re-emerged in 2004, and the disease persistently reduces cassava yields and storage root qualities. The spread of CBSD has been studied spatially in fields in different agroecologies. However, within-host distribution and accumulation of CBSV and UCBSV in naturally infected cassava plants is unknown. Therefore, within-host CBSV and UCBSV distribution was studied to correlate CBSD symptoms with virus titre in organs of infected cassava. Leaf, stem and storage root samples, with and without symptoms, were collected from 10 genotypes of field-grown cassava. Presence of CBSV and UCBSV was detected by RT-PCR and virus levels determined by qRT-PCR. CBSV was present in 100% of CBSD samples with symptoms, with 45·3% positive for presence of both CBSV and UCBSV. Tolerant cassava genotypes were infected with CBSV alone and accumulated higher titre in roots than in aerial organs. Susceptible genotypes were co-infected with CBSV and UCBSV and exhibited variation in virus titre in each organ. Across genotypes, virus titre was lowest in the youngest leaves and highest in mature non-senescing leaves. This information provides insight into the relationship between CBSV, UCBSV and their cassava host, and is valuable for CBSD resistance breeding, epidemiology studies and CBSD control. © 2015 British Society for Plant Pathology.

Asea G.,National Crops Resources Research Institute | Vivek B.S.,CIMMYT | Lipps P.E.,Ohio State University | Pratt R.C.,Ohio State University
Molecular Breeding | Year: 2012

Northern corn leaf blight (NCLB) caused by Exserohilum turcicum, gray leaf spot (GLS) caused by Cercospora zeae-maydis and maize streak caused by maize streak Mastrevirus (MSV) are the most destructive foliar diseases limiting maize production in sub-Saharan Africa. Most foliar diseases of maize are managed using quantitative (partial) resistance, and previous studies have reported quantitative trait loci associated with host resistance (rQTL). Our objective was to compare the genetic gain and costs resulting from phenotypic, genotypic, and marker-assisted selection of partially inbred lines derived from many families for resistance to infection by three foliar pathogens. We developed a population of 410 F2:3 families by crossing inbred line CML202 with a breeding line designated VP31. These families were planted in nurseries inoculated separately with each pathogen. We conducted one cycle of early generation pedigree selection using three different procedures, phenotypic, genotypic, and marker/phenotypic index, for improvement of resistance to each pathogen. We used simple sequence repeat (SSR) markers flanking six target rQTL associated with partial resistance. Broad- and narrow-sense heritability estimates were also obtained for the F2:3 families, and selected and non-selected F2:4 families. Genetic gains resulting from the selection procedures were determined. Gene action of the candidate rQTL was determined using orthogonal contrasts. Estimates of costs based on lower boundary values indicated that the cost of marker-based selection was lower than that of phenotypic selection. Our results indicate that molecular markers linked to target rQTL can facilitate pyramiding resistance to multiple diseases during early generation pedigree selection. © 2011 Springer Science+Business Media B.V.

Yada B.,Makerere University | Tukamuhabwa P.,Makerere University | Alajo A.,National Crops Resources Research Institute | Mwanga R.O.M.,National Crops Resources Research Institute
Crop Science | Year: 2010

Sweetpotato [Ipomoea batatas (L.) Lam] is a widely grown and consumed root crop in Uganda. A total of 1303 accessions of sweetpotato germplasm collected from 21 districts of Uganda were planted for morphological characterization. Forty morphological descriptors were scored on 1256 accessions 90 to 100 d after planting. Stepwise discriminant analysis showed that the discriminating power of 20 morphological traits was sufficient to differentiate the accessions. The level of morphological variation for the 40 traits estimated using the Shannon Weaver diversity index (H') ranged from 0.10 to 0.99, with an overall mean of 0.71 ±0.03, suggesting a highly diverse collection. Cluster analysis using the unweighted pair-group method using arithmetic averages grouped the 1256 accessions into 20 major clusters, with the number of accessions per cluster ranging from 15 to 166. The general leaf outline was highly correlated with leaf lobe type (r = 0.79) and leaf lobe number (r = 0.80) and were the predominant characters in grouping the accessions to clusters. No grouping of accessions based on region of origin was observed, suggesting movement of germplasm between regions. Approximately 70% of the accessions were morphologically distinct and a collection of 946 accessions was selected to represent Ugandan sweetpotato landrace diversity. The complete passport data for this collection is available at: © Crop Science Society of America.

Muyinza H.,National Crops Resources Research Institute | Talwana H.L.,Makerere University | Mwanga R.O.M.,International Potato Center | Stevenson P.C.,University of Greenwich
International Journal of Pest Management | Year: 2012

Host-plant resistance could be a useful tool for managing the weevils Cylas puncticollis and C. brunneus, which are major insect pests of sweetpotato in Africa. There is currently little information on existing resistance mechanisms against Cylas spp. in African cultivars, except where lower levels of weevil damage were attributed to escape due to deep rooting and reduced soil cracking, limiting the exposure of roots to weevils. Here, we evaluate weevil resistance in 134 sweetpotato cultivars and landraces over two seasons in two agroecologically diverse locations. Several sweetpotato cultivars, including New Kawogo, expressed resistance to Cylas spp. The resistance characteristics have been demonstrated in previous laboratory experiments to be quantifiable and thus potentially useful in targeted plant-breeding against Cylas spp. We showed external root and stem base damage to be an accurate quantitative indicator of internal root damage, offering rapid and accurate evaluation of resistance in field trials for screening. Moreover, weevil resistance can be assessed earlier in plant development, so saving time in the selection of the progeny from breeding programmes. © 2012 Taylor & Francis.

Ogwok E.,National Crops Resources Research Institute | Odipio J.,National Crops Resources Research Institute | Halsey M.,Donald Danforth Plant Science Center | Gaitan-Solis E.,Donald Danforth Plant Science Center | And 4 more authors.
Molecular Plant Pathology | Year: 2012

Cassava brown streak disease (CBSD), caused by the Ipomoviruses Cassava brown streak virus (CBSV) and Ugandan Cassava brown streak virus (UCBSV), is considered to be an imminent threat to food security in tropical Africa. Cassava plants were transgenically modified to generate small interfering RNAs (siRNAs) from truncated full-length (894-bp) and N-terminal (402-bp) portions of the UCBSV coat protein (ΔCP) sequence. Seven siRNA-producing lines from each gene construct were tested under confined field trials at Namulonge, Uganda. All nontransgenic control plants (n = 60) developed CBSD symptoms on aerial tissues by 6months after planting, whereas plants transgenic for the full-length ΔCP sequence showed a 3-month delay in disease development, with 98% of clonal replicates within line 718-001 remaining symptom free over the 11-month trial. Reverse transcriptase-polymerase chain reaction (RT-PCR) diagnostics indicated the presence of UCBSV within the leaves of 57% of the nontransgenic controls, but in only two of 413 plants tested (0.5%) across the 14 transgenic lines. All transgenic plants showing CBSD were PCR positive for the presence of CBSV, except for line 781-001, in which 93% of plants were confirmed to be free of both pathogens. At harvest, 90% of storage roots from nontransgenic plants were severely affected by CBSD-induced necrosis. However, transgenic lines 718-005 and 718-001 showed significant suppression of disease, with 95% of roots from the latter line remaining free from necrosis and RT-PCR negative for the presence of both viral pathogens. Cross-protection against CBSV by siRNAs generated from the full-length UCBSV ΔCP confirms a previous report in tobacco. The information presented provides proof of principle for the control of CBSD by RNA interference-mediated technology, and progress towards the potential control of this damaging disease. © 2012 BSPP AND BLACKWELL PUBLISHING LTD.

Onaga G.,National Crops Resources Research Institute | Asea G.,National Crops Resources Research Institute
Crop Protection | Year: 2016

Rice blast caused by Magnaporthe oryzae continues to be the most destructive disease of rice worldwide, and is a number one disease of rice in Uganda. We present the footprints of M. oryzae importance, distribution, incidence and severity in the rice growing agro-ecologies of Uganda for 2009/2010, and the potential mitigation measures. Our data show that rice blast affects more than 50% of the cultivated rice area on average, and ranks as the most important disease encountered in the field. Between and within agroecologies, both incidence and severity varied (P < 0.05) reflecting the contribution of different cropping practices on rice blast epiphytotics. The highest blast incidence and severities were recorded in Bugiri, Butaleja, Mbale and Lira farmlands, which are the ancestral rice cultivation areas in Uganda. These areas showed mean yield reductions of >30% relative to other locations, suggesting that rice production history played a significant role in rice blast outbreaks. Broadcasting and drill seeding yielded 42.4% less than transplanted rice. Growing two rice crops per year is one of the methods suggested to increase rice production in Uganda, but there was a higher disease incidence in the late season than in the early season, indicating the need for improved resistant varieties. Four blast resistance genes (Pi9, Piz-t, Pi19 and Piz-5) and the cultivar Tetep had the lowest (≤4) blast severity scores in all the test locations. It could be suggested that these genes are potential resistance sources for developing varieties, which would be more relevant for the double cropping systems. © 2015 Elsevier Ltd.

Yadav J.S.,Donald Danforth Plant Science Center | Ogwok E.,Donald Danforth Plant Science Center | Ogwok E.,National Crops Resources Research Institute | Wagaba H.,Donald Danforth Plant Science Center | And 7 more authors.
Molecular Plant Pathology | Year: 2011

Cassava brown streak disease (CBSD), caused by Cassava brown streak Uganda virus (CBSUV) and Cassava brown streak virus (CBSV), is of new epidemic importance to cassava (Manihot esculenta Crantz) production in East Africa, and an emerging threat to the crop in Central and West Africa. This study demonstrates that at least one of these two ipomoviruses, CBSUV, can be efficiently controlled using RNA interference (RNAi) technology in cassava. An RNAi construct targeting the near full-length coat protein (FL-CP) of CBSUV was expressed constitutively as a hairpin construct in cassava. Transgenic cassava lines expressing small interfering RNAs (siRNAs) against this sequence showed 100% resistance to CBSUV across replicated graft inoculation experiments. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed the presence of CBSUV in leaves and some tuberous roots from challenged controls, but not in the same tissues from transgenic plants. This is the first demonstration of RNAi-mediated resistance to the ipomovirus CBSUV in cassava. © 2011 The Authors. Molecular Plant Pathology © 2011 BSPP and Blackwell Publishing Ltd.

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