Development of Field Diagnostic Tools for and Characterisation of Xanthomonas campestris pathovar musacearum, Causal Agent of Banana Xanthomonas Wilt

Xanthomonas campestris pathovar musacearum (Xcm) is the causal agent of Xanthomonas Wilt (XW) of Bananas. It is currently the greatest threat to the existence and production of bananas in Uganda and other neighboring countries. XW on banana is able to cause about 80-100% field losses. There are currently no known chemicals, herbicides or resistant banana cultivars that can be used to control this disease. Despite awareness efforts among farmers, this disease continues to bring down the yield of bananas in growing areas. This is also due to the fact that symptoms caused by XW are similar to, and often indistinguishable from those caused by manageable common banana diseases such as Fusarium wilt. The key control strategy of XW is immediate destruction of infected plants. There is therefore need for early and accurate detection of Xcm: an onsite field detection tool. There are currently PCR (polymerase chain reaction) laboratory based assays and antibody based systems that are used for detection of this bacterium. This study developed another antibody-based system: an ELISA polyclonal antibody assay for Xcm formatted in to a lateral flow device (LFD). This study also introduces a new pathovar, Xanthomonas vasicola pv musacearum, to the species Xanthomonas vasicola and therefore carried out large scale comparative pathogenicity testing of the X.vasicola pathovars on maize, banana and sugarcane. This study further characterized a new collection of Xcm isolates from Western Uganda to determine their genotypes based on a subset of the 86 Single Nucleotide Polymorphisms that divided Xcm isolates into two major sub- lineages (I&II) as previously reported (Wasukira et al, 2012).Mcknight Foundation through Bioversity Internationa

Distribution and farmers’ knowledge on Fusarium wilt (Race 1) in cropping systems of Uganda

The study aimed at understanding the spatial distribution of Fusarium wilt (FW) in different banana growing regions, ascertain the effect of management practices and plantation age on FW incidence, as well as investigate farmers’ knowledge regarding the symptoms and spread of FW in Uganda. Individual interviews were conducted in 119 farms using a pre-tested questionnaire and field observations during a survey in major banana growing regions. Results indicate that FW is widely distributed across the banana growing areas with more occurrences (70%) in Kapchorwa district and majority of respondents (63.4%) reported increasing disease prevalence. A chi-square test performed revealed significant association between FW incidence and plantation age with more incidences (51.6%) recorded in older plantations (>20 years of establishment) than newly (1-5 years) established ones (11.1%). FW incidence was significantly associated with plantation management with higher incidences (86.9%) recorded in well managed plantations. Half of interviewed farmers could explain and distinguish symptoms associated with FW from other diseases, but only 38.4% of these could tell how the disease spreads; thus, a need for more concerted efforts in building the capacity of farmers to identify the symptoms and spread of FW for effective management program. We identified preliminary evidence that field abandonment is sometimes used as a last option for coping up with FW. Understanding the mechanism behind this requires more detailed research as well as establishing how farmers are managing FW culturally

Transfer of Xanthomonas campestris pv. arecae, and Xanthomonas campestris pv. musacearum to Xanthomonas vasicola (Vauterin) as Xanthomonas vasicola pv. arecae comb. nov., and Xanthomonas vasicola pv. musacearum comb. nov. and description of Xanthomonas vasicola pv. vasculorum pv. nov.

The "Ca2+ switch" model with cultured Madin-Darby canine kidney (MDCK) cells is useful in studying the biogenesis of epithelial polarity and junction formation and provides insight into early steps in the morphogenesis of polarized epithelial tissues. When extracellular Ca2+ in the medium is changed from less than 5 microM to 1.8 mM, MDCK cells rapidly change from a nonpolarized state exhibiting little cell-cell contact (with the apical membrane and junctional proteins largely within the cell) to a polarized state with well-formed tight junctions and desmosomes. To examine the role of intracellular Ca2+ in the development of polarity and junctions, we made continuous spectrofluorimetric measurements of intracellular Ca2+ during the "switch," using the fluorescent indicator fura-2. Intracellular Ca2+ increased greater than 10-fold during the switch and gave a complex pattern of increase, decrease, and stabilization. In contrast, intracellular pH [monitored with 29,79-bis(2-carboxyethyl)-5(and 6)-carboxyfluorescein (BCECF)] did not change during the period studied. When intracellular Ca2+ curves in several cells were compared, considerable heterogeneity in the rate of increase of intracellular Ca2+ levels and in peak levels was evident, perhaps reflecting the heterogeneity among cells in establishing junctions and polarity. The heterogeneity of the process was confirmed by digital imaging of intracellular Ca2+ and was present even in a "clonal" line of MDCK cells, indicating the heterogeneity was intrinsic to the process and not simply a function of slight genetic variation within the population of MDCK cells. In pairs of cells that had barely established cell-cell contact, often one cell exhibited a much greater increase in intracellular Ca2+ than the other cell in the pair. At the site of cell-cell contact, an apparent localized change (an increase over the basal level) in intracellular Ca2+ was frequently present and occasionally appeared to extend beyond the point of cell-cell contact. Since the region of cell-cell contact is also the site where junctions form and where vesicles containing apical membranes fuse during the development of polarity, we postulate a role for global and local changes in intracellular Ca2+ in these events