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Omondi P.A.,Climate Prediction and Applications Center | Awange J.L.,Curtin University Australia | Forootan E.,University of Bonn | Ogallo L.A.,Climate Prediction and Applications Center | And 11 more authors.
International Journal of Climatology | Year: 2014

Recent special reports on climate extremes have shown evidences of changes in the patterns of climate extremes at global, regional and local scales. Understanding the characteristics of climate extremes at regional and local levels is critical not only for the development of preparedness and early warning systems, but is also fundamental in the development of any adaptation strategies. There is still very limited knowledge regarding the past, present and future patterns of climate extremes in the Greater Horn of Africa (GHA). This study, which was supported by the World Bank Global Facility for Disaster Reduction and Recovery (WB-GFDRR) and implemented by the World Meteorological Organization, was organized in terms of three workshops with three main objectives; (1) analysis of daily rainfall and temperature extremes for ten countries in the GHA region using observed in situ data running from 1971 to 2006, (2) assessing whether the United Kingdom Met-office and Hadley centre Providing REgional Climates for Impact Studies (UK-PRECIS) modelling system can provide realistic representation of the past and present climate extremes as observed by available in situ data, and (3) studying the future regional climate extremes under different scenarios to further assess the expected changes in climate extremes. This paper, therefore, uses the outputs of these workshops and also includes post-workshop analyses to assess the changes of climate extremes within the GHA. The results showed a significant decrease in total precipitation in wet days greater than 1mm and increasing warm extremes, particularly at night, while cold extremes are decreasing. Considering a combination of geophysical models and satellite gravimetry observations from the Gravity Recovery and Climate Experiment (GRACE) mission in the frame of GRACE daily Kalman-smoothing models, for the years 2002 to 2010, we explored a decline in total water storage variations over the GHA. © 2013 Royal Meteorological Society. Source


Kagoda F.,National Agricultural Research Organization | Hearne S.,International Institute Of Tropical Agriculture | Adewuyi O.,International Institute Of Tropical Agriculture | Coyne D.L.,International Institute Of Tropical Agriculture
Euphytica | Year: 2015

Maize is the most important cereal food crop is sub-Saharan Africa though yields are below their potential. Among the factors which limit yield, drought stress is one of the most pervasive. The ability of a crop to produce grain under drought (water) stress is governed by many factors including nematodes. The aim of the current study was to determine the response of drought tolerant maize inbreds to nematode attack, understand the interaction between nematode infestation and water stress on maize growth and yield. The study comprised three factors: optimal irrigation against water stress, five nematode treatment conditions and ten maize inbreds. Results showed irrigation option × genotype interaction to significantly affect growth of the maize crop from 6 weeks after planting. Water stress favoured the reproduction of lesion nematodes (Pratylenchus zeae), 50 times more than root knot nematodes (Meloidogyne incognita), which showed an increase in most inbreds only under optimal irrigation. Inbreds ACR.SYN-W, La Posta Seq. C7, TZL Comp1C4 and 5057 displayed resistance to P. zeae and M. incognita under water stress, although cob dry weights were low for TZL Comp1C4 and 5057. Inbreds BMB23, DTPL-W-C7 and TZEI1 displayed tolerance to P. zeae and M. incognita under water stress. Overall, there is a high possibility of extracting desired genetic combination for P. zeae/M. incognita resistant and drought tolerant genes from inbreds ACR.SYN-W and La Posta Seq. C7. © 2015, Springer Science+Business Media Dordrecht. Source


Ramathani I.,Makerere University | Biruma M.,Makerere University | Biruma M.,National Agricultural Research Organization | Martin T.,Swedish University of Agricultural Sciences | And 2 more authors.
European Journal of Plant Pathology | Year: 2011

In order to understand the underlaying causes of new severe turcicum leaf blight outbreaks in East Africa, a survey was undertaken in Uganda to examine the sorghum-Setosphaeria turcica interaction in terms of disease severity and incidence, the overall fungal population structure, and new resistant resources. Highest disease severities were recorded on caudatum accessions, whereas kafir genotypes were most resistant. The disease was more severe in the most humid farmlands compared to moderately dry agro-ecologies. In districts with wide adoption of the Epuripur variety a very high incidence (100%) of turcicum leaf blight was found. The two S. turcica mating type genes MAT1-1 and MAT1-2 assessed on fungal isolates deriving from both sorghum and maize diseased leaves were found in 20 of 23 districts sampled and in equal proportions. Upon cross inoculation on maize differential lines, four S. turcica isolates were identified as race 1, two as race 2, and one isolate corresponded to race 0 and race 3, respectively. The remaining 10 S. turcica isolates did not cause any disease symptoms on the maize lines assessed. Highly resistant accessions originating from a regional collection were found among the five sorghum races (kafir, guinea, caudatum, bicolor and durra), and are now implemented in new sorghum disease resistance programs. © 2011 KNPV. Source


Ssekiwoko F.,National Agricultural Research Organization | Turyagyenda L.F.,Bioversity International | Mukasa H.,Bioversity International | Eden-Green S.,EG Consulting | Blomme G.,Bioversity International
Acta Horticulturae | Year: 2010

Xanthomonas campestris pv. musacearum (Xcm) causes Xanthomonas wilt of banana (Musa spp.) and enset (Ensete ventricosum) in East and Central Africa. The disease is spread by insects that visit the male inflorescence, through the use of infected planting materials and by contaminated garden tools. To evaluate the most appropriate control options, the spread of bacteria within the plant following natural flower infection was studied in Luwero and Mpigi districts of central Uganda. Banana tissue samples were collected from the corm, true stem and leaf sheaths of 'Pisang Awak' (ABB genome) and 'Matooke' (AAA genome) mother plants, showing four progressive stages of disease development: stage 1 - male bud wilting; stage 2 - decaying rachis; stage 3 - premature fruit ripening; and stage 4 - rotting of fruit bunches. Thirty plants were sampled per stage and per cultivar. Additional samples were taken from attached suckers. Bacteria were isolated from surface-sterilized plant samples and identified by colony characteristics on a semiselective medium. Following inflorescence infection, Xcm moved along the true stem, into the youngest leaf sheaths inserted on the true stem, down into the corm and into the older leaf sheaths. At early stages of inflorescence infection (stage 1), bacteria were restricted to the upper parts of the true stem in 'Pisang Awak', but had moved further down the stem in 'Matooke'. Therefore, cutting down mother plants at stage 1 could stop Xcm from reaching the corm and eventually crossing to the suckers of 'Pisang Awak' but this was less likely to be effective for 'Matooke' plants. The bacteria were recovered from suckers of both cultivars showing symptoms at stage 4, but at stage 3 only from 'Pisang Awak'. It is recommended that whole mats should be completely uprooted or killed by herbicides in case mother plants show symptoms beyond stage 1 for 'Pisang Awak' and at all disease symptom stages for 'Matooke'. Source


Ocimati W.,Bioversity International | Ssekiwoko F.,National Agricultural Research Organization | Karamura E.,Bioversity International | Tinzaara W.,Bioversity International | And 2 more authors.
Plant Pathology | Year: 2013

Banana xanthomonas wilt (XW) caused by Xanthomonas campestris pv. musacearum (Xcm) attacks all banana cultivars. Xcm in inflorescence-infected Pisang Awak plants with wilting male bud bracts is restricted to the upper parts of the true stem; therefore, cutting these plants at the pseudostem base has been recommended to prevent further Xcm spread. In order to fine-tune existing control strategies, this study examined the movement of Xcm into plants and mats, in relation to disease incubation period. Mature Pisang Awak and East African highland (AAA-EA) plants were inoculated with Xcm through abscission wounds of female bracts, male bud bracts, male flowers, a combination of male bud bracts and flowers, and by cutting male buds with a contaminated machete. Thirty plants per genotype and treatment were monitored for 24 months for disease symptoms. An additional 68 AAA-EA and 33 Pisang Awak plants were sampled weekly to assess the rate of Xcm spread within the plants. All floral entry points resulted in disease, with the highest incidence in combined male bract and male flower abscission wound inoculations. The study confirmed the systemicity of Xcm, with the pathogen able to live within the mat for long periods (5-16 months) without causing disease. Reliance on disease symptom expression to manage XW is therefore not sufficient. The long incubation period in lateral shoots may explain the current resurgence of the disease in locations where the disease was thought to have been successfully eradicated. © 2012 The Authors Plant Pathology © 2012 BSPP. Source

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