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Summary: Considered responsible for one million deaths in Ireland and widespread famine in the European continent during the 1840s, late blight, caused by Phytophthora infestans, remains the most devastating disease of potato (Solanum tuberosum L.) with about 15%–30% annual yield loss in sub‐Saharan Africa, affecting mainly smallholder farmers. We show here that the transfer of three resistance (R) genes from wild relatives [RB, Rpi‐blb2 from Solanum bulbocastanum and Rpi‐vnt1.1 from S. venturii] into potato provided complete resistance in the field over several seasons. We observed that the stacking of the three R genes produced a high frequency of transgenic events with resistance to late blight. In the field, 13 resistant transgenic events with the 3R‐gene stack from the potato varieties 'Desiree' and 'Victoria' grew normally without showing pathogen damage and without any fungicide spray, whereas their non‐transgenic equivalent varieties were rapidly killed. Characteristics of the local pathogen population suggest that the resistance to late blight may be long‐lasting because it has low diversity, and essentially consists of the single lineage, 2_A1, which expresses the cognate avirulence effector genes. Yields of two transgenic events from 'Desiree' and 'Victoria' grown without fungicide to reflect small‐scale farm holders were estimated to be 29 and 45 t/ha respectively. This represents a three to four‐fold increase over the national average. Thus, these late blight resistant potato varieties, which are the farmers' preferred varieties, could be rapidly adopted and bring significant income to smallholder farmers in sub‐Saharan Africa. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

A field screening trial undertaken in Uganda showed that a number of Musa L. (Musaceae) cultivars and hybrids displayed high levels of resistance to banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), while most highland banana cultivars tended to be susceptible to weevil attack. In this study, research was undertaken to determine modalities of resistance to banana weevil. Laboratory studies suggested that all cultivars were attractive to the weevil and that females freely oviposited on all cultivars. While some differences were found between cultivars in attractivity and egg numbers, these were not related to subsequent damage. Therefore, antixenosis does not appear to play an important role in host-plant resistance to banana weevil. Larval survivorship rates in living corms were, for the most part, low on resistant cultivars, suggesting that antibiosis mechanisms offer the primary avenues of resistance. In the laboratory, development was slower on some resistant cultivars although survivorship rates on excised corm material were not as well related to levels of resistance as that on living material. Sap appeared to play a minor role in reducing egg eclosion rates on some resistant cultivars. Methanol extracts from Kayinja, a resistant cultivar, inhibited larval development on corms of susceptible cultivars in the laboratory. [ABSTRACT FROM AUTHOR]

Between 1970 and 1990 Uganda witnessed the decline of the highland cooking banana from traditional growing areas in the central region, coupled with crop expansion in the country's southwest. Apprehension that the factors leading to loss of sustainability in. the central region may be replayed in extant production areas has raised concern about the future of the cooking banana in Uganda. Consequently, a multi-disciplinary study was conducted at nine central and six southwesternsites to document shifts in cooking banana production and to elucidate the causes behind these shifts. Cooking banana production in central Uganda sites fell from 18% of total food crop and 7% of total cashcrop production in the 1970s to 4% and 2%, respectively, in the 1990s. Farmers identified reduced labour availability and management, increasing pest pressure and declining soil nutrient status as the majorcauses of decline. On-farm verification confirmed farmers' observations: weevil levels were the highest yet found in Uganda, while foliarsamples indicated deficiencies in magnesium, nitrogen, and potassium. Soil nutrient deficiencies, however, appear to be a direct outcome of reduced management rather than 'soil exhaustion' as postulated by farmers. In southwestern Uganda, the importance of the cooking bananaas a cash crop has quadrupled since 1970. Banana first penetrated the region because of its ease of production and stability of yield. High yields attracted traders and urban market demand drove further crop expansion. With current market incentives, banana management standards have been high. Under current levels of management, it is unlikely that farmers in southwestern Uganda will experience a similar process of decline as that which occurred in the central region. However, concern remains about lack of replenishment of nutrients leaving the farm in the form of fruits sold for market, a nutrient loss which mayeventually lead to non-sustainability of the cropping system. [ABSTRACT FROM AUTHOR]