Progress in achieving household food security in climate-smart villages in the Albertine Rift, western Uganda

Hoima is located in western Uganda east of Lake Albert, on a landscape that is generally undulating with relatively flat low lying area alternating with broad hills. The area has a population density of 160 persons per square kilometer, with 22% of the people living below the poverty line. The area faces land degradation and declining soil fertility. The key food crops are cassava, beans, sweet potatoes, and maize. Chicken, pigs, cows and goats are important for food and income generation. Most households get their food supplies from their own farms throughout the year. The worst months for food supplies, when more than 20% of households get their food mainly from off-farm sources and 40% of the households have food deficits are March and April, which also mark the beginning of the rains after several months of dry season. About 31% of households are food secure all year long. Another 35% suffer food deficits for 1-2 months per year. 16% of these households struggle to get enough to feed their families for 3-4 months, 9% for 5-6 months, and 10% for more than six months per year

The mechanism of resistance to Xanthomonas vasicola pv musacearum explored in Musa balbisiana

Banana Xanthomonas wilt caused by Xanthomonas vascicola pv musacearum (Xvm) devastates banana in East and Central Africa causing total yield loss in diseased plants. Previous germplasm screening experiments has identified M. balbisiana, a wild banana type, as an important Xvm resistance source but with exact resistance mechanism still to be defined. This PhD study was therefore aimed to evaluate the possible mechanism. For the study, clean M. balbisiana plantlets were required that were obtained through a newly developed tissue culture process. In the absence of a suitable banana culture medium, the MS proliferation medium was, in a first step, modified by increasing concentrations of the antioxidants ascorbic acid and thiamine-HCl to 20 mg/l and 0.18 mg/l, respectively. In addition, culturing the explants in total darkness for the first 9 weeks after initiation improved plantlet proliferation. Modifications applied enabled production of up to 40 M. balbisiana plantlets per explant. In a further step, multiplication and migration of Xvm in M. balbisiana plantlets following injection was investigated and compared to susceptible banana EAHB cv Nakinyika . Treatment of the youngest open leaf with a bacterial suspension delayed symptom development in M. balbisiana and symptoms only appeared 10 weeks after inoculation. In addition, wilt incidence and severity were only 33% and 20%, respectively, with only the symptomatic leaves, inoculated and the immediate follower leaves, eventually dying. In addition, a general decline in the population of the bacterium in the plant occurred, though the bacterium initially migrated to the leaves that are immediate followers to the inoculated leaf. In a further molecular dissection of the active defense pathway, a sharp decline in transcription of several genes involved in pathogen resistance was found. After inoculation, transcription of MbNBS (an R gene), MdNPR1 (NPR1 gene) and PR3 (a typical PR gene) was below basal transcription in both resistant M balbisiana and susceptible banana EAHB cv Nakinyika indicating that Xvm can limit the banana?s ability to timely detect and set up effective defenses in both resistant and susceptible banana. Gene transcription recovered, however, above basal transcription in later infection stages in resistant M balbisiana, although this did not prevent wilt symptoms from eventually developing. Investigation into M balbisiana resistance also identified heat stable pre-existing compounds soluble in methanol that can inhibit Xvm growth in-vitro. Overall, this PhD study has identified resistance gene expression and formation of secondary compounds as potential contributors to M balbisiana resistance to Xvm.Thesis (PhD)--University of Pretoria, 2016.Plant SciencePhDUnrestricte

Fine-tuning banana Xanthomonas wilt control options over the past decade in East and Central Africa

Xanthomonas wilt, caused by Xanthomonas campestris pv. musacearum has, since 2001, become the most important and widespread disease of Musa in East and Central Africa. Over the past decade, new research findings and especially feedback from small-scale farmers have helped in fine-tuning Xanthomonas wilt control options. During the initial years of the Xanthomonas wilt epidemic in East Africa, the complete uprooting of diseased mats and the burning or burying of plant debris was advocated as part of a control package which included the use of clean garden tools and early removal of male buds to prevent insect vector transmission. Uprooting a complete mat (i.e. the mother plant and a varying number of lateral shoots) is understandably time-consuming and labour intensive and becomes very cumbersome when a large number of diseased mats have to be removed. Recent research findings suggest that Xcm bacteria do not colonize all lateral shoots (i.e. incomplete systemicity occurs) and even when present that this does not necessarily lead to symptom expression and disease. This led to a new control method whereby only the visibly diseased plants within a mat are cut at soil level. The underlying idea is that the continued removal of only the diseased plants in a field will reduce the inoculum level and will bring down disease incidence to an acceptable level. This method is less labour intensive and takes a short time compared to the removal of a complete mat. However, single diseased stem removal needs to go hand in hand with prevention of new infections that can occur through the use of contaminated garden tools or through insect vector transmission. Novel transgenic approaches are also discussed. This paper presents an overview of past and ongoing research towards the development of a more practical and less demanding control strategy for Xanthomonas wilt