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Mumbanza F.M.,National Banana Research Programme | Mumbanza F.M.,Makerere University | Kiggundu A.,National Agricultural Research Laboratories | Tusiime G.,Makerere University | And 3 more authors.
Pest Management Science

BACKGROUND: A key challenge for designing RNAi-based crop protection strategies is the identification of effective target genes in the pathogenic organism. In this study, in vitro antifungal activities of a set of synthetic double-stranded RNA molecules on spore germination of two major pathogenic fungi of banana, Fusarium oxysporum Schlecht f. sp. cubense WC Snyder & HN Hans (Foc) and Mycosphaerella fijiensis Morelet (Mf) were evaluated. RESULTS: All the tested synthetic dsRNAs successfully triggered the silencing of target genes and displayed varying degrees of potential to inhibit spore germination of both tested banana pathogens. When Foc dsRNAs were applied to Foc spores, inhibition ranged from 79.8 to 93.0%, and from 19.9 to 57.8% when Foc dsRNAs were applied to Mf spores. However, when Mf dsRNAs were applied on Mf spores, inhibition ranged from 34.4 to 72.3%, and from 89.7 to 95.9% when Mf dsRNAs were applied to Foc spores. CONCLUSION: The dsRNAs for adenylate cyclase, DNA polymerase alpha subunit and DNA polymerase delta subunit showed high levels of spore germination inhibition during both self- and cross-species tests, making them the most promising targets for RNA-mediated resistance in banana against these fungal pathogens. © 2013 Society of Chemical Industry. Source

Bagamba F.,National Banana Research Programme | Bagamba F.,Makerere University | Burger K.,Development Economics Leeuwenborch Hollandseweg | Tushemereirwe W.K.,National Banana Research Programme
Acta Horticulturae

The highland cooking banana (Musa spp., AAA-EA genome) is the most important crop in the East African Great Lakes region. In Uganda, production has expanded and productivity increased in the country's southwest and declined in the Central region where the crop has traditional roots. Analyzing crop characteristics and performance was imperative to elucidate the factors that have contributed to this change. Performance analysis helps to inform possible investment policies and strategies in the banana subsector for both regions. The study was carried out in central and southwest regions of the country, which have divergent production constraints and opportunities. Changes in economic conditions appear to have contributed to the shift in banana production from the central to the southwest. Specifically, increase in nonfarm-farm income in the central region reduced farmers' need for cash income generated from farm production. On the other hand, high food prices increased farmers' need to rely on own farm production for household needs. There was a shift in resource allocation in favor of crops most suited to satisfying household food needs (e.g., sweet potato (Lpomoea batatas), cassava (Manihot esculenta) and beans (Phaseolus spp.) against crops that appear to be more profitable (e.g., bananas) when valued at farm-gate prices. In the southwest, farmers adopted technologies and crop activities that were relatively more labor demanding but more rewarding in terms of cash benefits. Specifically, bananas were adopted because they satisfied both the cash needs and food requirements of the farmers. However, a significant proportion of land (not suited to banana production) in the southwest (15.4%) is committed to finger millet (Eleusine coracana) production to supplement bananas in terms of food security. Source

Adriko J.,Copenhagen University | Adriko J.,National Agricultural Biotechnology Center | Adriko J.,National Banana Research Programme | Mbega E.R.,Copenhagen University | And 6 more authors.
European Journal of Plant Pathology

A PCR-based system was developed to reliably and robustly identify group I and II members of the genus Xanthomonas. Primer sets developed from three gene targets namely fyuA, ITS and gumD were evaluated in the study. Primer sets were evaluated using DNA extracted from 45 Xanthomonas strains representing 25 species broadly covering the genus. Fifteen non-Xanthomonas strains of plant-associated bacteria including phylogenetically closely related species Stenotrophomonas maltophilia and Xylella fastidiosa were also tested. The primers targeting fyuA amplified DNA from all xanthomonads except X. theicola, while the ITS primers amplified a DNA fragment of 254 bp in all 45 Xanthomonas strains; whereas no amplification was observed for non-xanthomonads. The gumD primers allowed efficient amplification of DNA in 38 out of 39 isolates from Group II, whereas no or very weak amplification occurred with DNA from Group I members. Internal controls of primers targeting bacterial 16S rDNA or plant 26S mitochondrial rDNA were successfully applied in multiplex PCRs for testing bacterial cultures or plant tissue, respectively. The findings give us a PCR based approach that can reliably and effectively differentiate xanthomonads from non-xanthomonads as well as separating the strains belonging to the two described groups of the genus Xanthomonas. The study thus offers valuable tools for disease surveillance and management. It can effectively be applied in rapid assessment of new disease occurrences, for which no specific detection tools could be in place. © 2013 KNPV. Source

Adriko J.,Copenhagen University | Adriko J.,National Banana Research Programme | Aritua V.,University of Florida | Mortensen C.N.,Copenhagen University | And 3 more authors.
Plant Pathology

The present study developed a pathovar-specific PCR for the detection of Xanthomonas campestris pv. musacearum (Xcm), the cause of banana xanthomonas wilt, by amplification of a 265-bp region of the gene encoding the general secretion pathway protein D (GspD). A distinct DNA fragment of the expected size was amplified from genomic DNA from all of 12 Xcm isolates tested and no amplification of DNA was observed from other xanthomonads or plant-associated bacteria, including the two closely related species Xanthomonas vasicola pv. holcicola and Xanthomonas axonopodis pv. vasculorum. The Xcm-specific PCR was successfully multiplexed with internal control primers targeting 16S rDNA for application on DNA from bacterial cultures and with primers targeting plant mitochondrial 26S rDNA for application on DNA extracted from plant material. Diagnostic discrimination of healthy and infected plants was subsequently demonstrated in tests on artificially inoculated screenhouse cultivars of banana and field bananas with and without symptoms sampled from different parts of Uganda. This study therefore demonstrated a robust and specific Xcm diagnostic tool with the added advantage of applying internal PCR controls for direct quality assessment of results. © 2011 The Authors. Plant Pathology © 2011 BSPP. Source

Barekye A.,University of KwaZulu - Natal | Barekye A.,National Banana Research Programme | Tongoona P.,University of KwaZulu - Natal | Derera J.,University of KwaZulu - Natal | And 2 more authors.
Field Crops Research

The generation of banana triploids from tetraploid-diploid crosses requires knowledge on the influence of the parents on black Sigatoka resistance and agronomic traits to the triploid progenies. The objective of this investigation was to determine the influence of tetraploid and diploid parents on black Sigatoka resistance and agronomic traits in the triploid progenies generated from tetraploid-diploid crosses. The mating scheme was designed as a 4 × 5 North Carolina II mating design. Due to problems in seed set and germination, progenies from 2 male parents with 4 female parents were evaluated at two sites in Uganda. The results showed that the male-parent triploid progeny heritability estimate for the number of leaves at harvest was greater than the female parent estimate. The diploid parents had higher correlation coefficients for the total leaves at harvest with the triploid progenies than tetraploid parents with triploid progenies. Disease development over time took more days in diploid parents than in the tetraploid parents with the triploid progenies as intermediates. These results suggested that diploids transferred black Sigatoka resistance to the triploid progenies as measured by the number of standing leaves and disease development overtime. There was a positive correlation (P<0.05) between tetraploid female parents and triploid progenies for plant height and bunch weight. The triploid progeny-tetraploid female parent heritability estimates for plant height (0.92) and bunch weight (0.72) were highly significant. These results indicated that the female synthetic tetraploids influenced plant height and bunch weight in the triploid progenies. Therefore, it is important to select the tetraploids with heavy bunches to effectively improve yield in triploid progenies generated by tetraploid-diploid crosses. The tetraploid-diploid progenies had a significant (P<0.05) family-by-site interaction for bunch weight indicating that new banana genotypes need to be tested across different environments to select stable genotypes to promote to end-users. © 2011 Elsevier B.V. Source

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