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Kovacs G.,Catholic University of Leuven | Sagi L.,Catholic University of Leuven | Sagi L.,Hungarian Academy of Sciences | Jacon G.,Catholic University of Leuven | And 8 more authors.
Transgenic Research | Year: 2013

Transgenic banana (Musa acuminata 'Gros Michel') integrating either of two rice chitinase genes was generated and its resistance to Black Leaf Streak disease caused by the fungus Mycosphaerella fijiensis was tested using a leaf disk bioassay. PCR screening indicated the presence of the hpt selectable marker gene in more than 90 % of the lines tested, whereas more than three quarters of the lines contained the linked rice chitinase gene resulting in a co-transformation frequency of at least 71.4 %. Further, a unique stable integration of the transgenes in each line revealed some false negative PCR results and the expected co-transformation frequency of 100 %. The transgene insert number per line ranged from 1 to 5 and single transgene insert lines (25 % of all) were identified. Considerable delay in disease development (up to 63 days post-incoculation) over a monitoring period of 108 days occurred in nine lines with extracellularly targeted chitinase out of 17 transgenic lines tested and their necrotic leaf area decreased by 73-94 % compared to the untransformed susceptible control line. Finally, correlation between symptom development and rice chitinase expression was confirmed in two lines by Western analysis. The potential of rice chitinase genes to enhance resistance against M. fijiensis in banana was demonstrated as well as the usefulness of the leaf disk bioassay for early disease screening in transgenic banana lines. © 2012 The Author(s).

Tumuhimbise R.,National Agricultural Research Laboratories
Journal of Crop Improvement | Year: 2015

Taro is a marginalized tuber food crop, with wide distribution in the tropics. This study was aimed at assessing the effects of plant spacing and planting depth on corm yield and yield-related traits in taro. Dasheen, a predominant taro cultivar in Uganda, was sourced from farmers’ fields and evaluated using a randomized complete block design for two seasons. Three plant spacings (0.30 × 0.30 m, 0.50 × 0.50 m, 0.75 × 0.75 m) and two planting depths (0.15 m and 0.30 m) were used. Plant spacing had a significant effect on plant height, corm girth, corm yield plant−1, shoot yield plant−1 and corm yield hectare−1 (ha−1). Planting depth had a significant effect on corm length and corm yield ha−1. The widest spacing (0.75 × 0.75) produced largest corm yield plant−1 and shoot yield plant−1, whereas the narrowest spacing (0.30 × 0.30 m) produced largest shoot yield ha−1 and corm yield ha−1. Planting depth of 0.30 m produced higher corm yield and length than that of 0.15 m. Plant spacing was positively and significantly correlated with plant height, corm girth, and shoot yield plant−1 but negatively correlated with corm yield ha−1 and shoot yield ha−1. Planting depth was positively and significantly correlated with corm length, indicating that deeper planting of taro produced longer corms, thus enhancing corm yield. Copyright © Taylor & Francis Group, LLC.

Mulumba J.W.,Plant Genetic Resources Center | Lwasa J.,National Agricultural Research Laboratories | Atieno F.,Bioversity International
African Journal of Ecology | Year: 2011

The aim of the study was to map the distribution of Acacia senegal and its infraspecific taxa in Uganda and predict its suitable range of occurrence based on climatic factors. The distribution of the infraspecific taxa was analysed for richness, diversity, turnover and reserve selection. Regression analysis was performed to understand the relationship between distribution of the species and climatic variables. Georeferenced species occurrence points were superimposed over temperature and vapour maps. Areas with highest taxa richness, diversity and turnover were mapped and found in the Lake Kyoga basin. The species shows preference for the northern region of the study area with dissimilar climatic pattern from the southern region and the superimposition supported findings. Variety kerensis exhibited narrower climatic, altitudinal and distribution range preference. Temperature seasonality, maximum temperature of warmest month, temperature annual range, mean temperatures of warmest and driest quarters had the highest coefficients of determination (r2>0.7) hence most important in influencing species distribution. The most appropriate locations for in situ conservation and for germplasm collection to ensure maximum diversity is secured are found in Wabisi-Wajala, Kiula, Kyalubanga, Bajo, Kasagala, Kabwika-mujwalanganda, Maruzi, Moroto and Napak Central Forest Reserves. The study recommends ecological studies to understand status of A. senegal. © 2011 Blackwell Publishing Ltd.

Tumuhimbise R.,University of KwaZulu - Natal | Tumuhimbise R.,National Agricultural Research Laboratories | Melis R.,University of KwaZulu - Natal | Shanahan P.,University of KwaZulu - Natal
Field Crops Research | Year: 2014

Little progress has been made in determining the combining ability and gene action controlling early storage root yield (SRY) and disease resistance traits in the Ugandan cassava germplasm. Such information is important in the selection of parents and breeding strategies for an effective breeding programme. The objective of this study was to estimate the general combining ability (GCA) of nine cassava parents and their specific combining ability (SCA) for early SRY and disease resistance traits, as well as to determine the gene action controlling these traits. Thirty-six full-sib cassava families were generated from a 9. ×. 9 half-diallel mating design and were evaluated in two distinct environments in Uganda using a 3. ×. 12 row by column design. Family, GCA and SCA effects and their interactions with environments were significantly different for most traits, indicating, respectively significant differences in the mean performances of the families, additive and non-additive gene action in the expression of the traits, and the non-additive influence of the environments. The relative importance of additive and non-additive gene action varied between traits, indicating the need for specific breeding strategies for each trait. Parents with desirable GCA effects for most traits were developed from cassava introductions from South America, highlighting their importance and possibility of widening genetic variability of African cassava germplasm. The GCA effects for the parents did not always correlate with their per se performance, implying that selection of parents based on their per se performance may not necessarily lead to development of superior hybrids. © 2014 Elsevier B.V.

Tumuhimbise R.,University of KwaZulu - Natal | Tumuhimbise R.,National Agricultural Research Laboratories | Shanahan P.,University of KwaZulu - Natal | Melis R.,University of KwaZulu - Natal | Kawuki R.,National Crops Resources Research Institute
Journal of Agricultural Science | Year: 2015

SUMMARY Cassava (Manihot esculenta Crantz) is an important storage root crop with largely unexplored and unexplained potentially valuable genetic variability. Genetic variability is important in selecting suitable genotypes for crop improvement. The present study was aimed at assessing the extent of variability in cassava storage root bulking, based on fresh storage root yield accumulated over time. Twelve cassava genotypes were evaluated in a randomized complete block design at three contrasting locations in Uganda. Assessments were done from 5 to 13 months after planting at intervals of 2 months. Genotype, harvest time, location and their interactions were significantly different for fresh storage root yield and most of the other traits assessed. Estimates of variance components revealed that a large portion of the phenotypic variance was accounted for by the genotypic component for all traits assessed indicative of substantial genetic variability among the genotypes evaluated. This genetic variability is important in a hybridization and/or selection programme because it implies that significant genetic gain through phenotypic selection is possible for the traits assessed. Fresh storage root yield was positively and significantly correlated with storage root girth, harvest index, shoot mass and storage root number. The information generated will inform future breeding initiatives to develop early-bulking cassava genotypes with farmer-preferred traits in Uganda. Copyright © Cambridge University Press 2014.

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