Data collection with farmers in bean pest and disease management using the Open Data Kit

Data collection with ODK part of a 3 –year project aimed at Supporting investments for upscaling of grain legumes in western Kenya through assessing and modeling the threat of biotic stressors

Effect of local inoculum on the spread of sweetpotato virus disease: limited infection of susceptible cultivars following widespread cultivation of a resistant sweetpotato cultivar

A study compared the spread of sweet potato virus disease (SPVD) into crops of two moderately resistant and initially SPVD-free sweet potato cultivars in northern and southern Mpigi, Uganda. Whiteflies, the vector of sweet potato chlorotic stunt crini virus (SPCSV), a component cause of SPVD, were similarly abundant in farmers' sweet potato fields around Namulonge in northern Mpigi, and Kanoni in southern Mpigi. However, mean incidence of SPVD in farmers' crops neighbouring the trials was higher at Kanoni (13·3%) than at Namulonge (2·8%). Furthermore, spread of SPVD into initially SPVD-free sweet potato plots of two only moderately resistant cultivars was greater in plots at Kanoni than in plots at Namulonge. The SPVD-resistant New Kawogo was the most common cultivar grown in farmers' fields at Namulonge and had few diseased plants, whereas susceptible cultivars with relatively high incidences of disease predominated at Kanoni. Final SPVD incidence in each trial was positively correlated with a measure combining the proximity and level of inoculum in surrounding fields. The study demonstrates the importance of local SPVD inoculum in determining the rate of spread of the disease into fields and implies that the widespread cultivation of a resistant variety limits infection of susceptible cultivars grown nearb

Genetic homogeneity among Ugandan isolates of Xanthomonas campestris pv. musacearum revealed by randomly amplified polymorphic DNA analysis

Open Access JournalThe Random Amplification of Polymorphic DNA (RAPD) analysis was used to detect the genetic diversity among Ugandan isolates of Xanthomonas campestris pv. musacearum (Xcm), the causal agent of banana Xanthomonas wilt (BXW) disease. Seven random primers were used because of their ability to amplify reproducible and reliable fingerprints generated between 6 - 12 amplicons each from the Xcm isolates obtained from central core of pseudostems, peduncles, fruit peelings, sap, nectar,insects’ bodies and bacterial oozes. Regardless of the source and geographical origin, similar fingerprints were generated from the tested isolates. Using a similarity coefficient of 58%, the unweighted pair group method with arithmetic averaging (UPGMA) analysis did not reveal any significant differences in clustering, with exception of a single isolate that had unique fingerprints. Prior to the genetic analysis, all the isolates compared showed no significant difference (P = 0.92) with regard to incubation period for appearance of symptoms and the severity of symptoms in pathogenicity test. Thus, our data indicates that the population of Xcm in Uganda is clonal, that is, one uniform population being spread fast and efficiently, suggesting that there is a low likelihood of the current population to rapidly evolve, in the near future, into more virulent strains to overcome any resistance deployed

Development of a semi selective medium for isolating Xanthomonas camprestris pv. musacearum from insect vectors, infected plant material and soil

A semiselective medium was developed for isolating Xanthomonas campestris pv. musacearum (Xcm) from infected banana plants, soil and insect vectors. The new medium was named cellobiose-cephalexin agar (CCA) and it contained (L−1): 1 g yeast extract, 1 g glucose, 1 g peptone, 1 g NH4Cl, 1 g MgSO4•7H2O, 3 g K2HPO4, 1 g beef extract, 10 g cellobiose, 14 g agar, 40 mg cephalexin, 10 mg 5-fluorouracil and 120 mg cycloheximide. The medium was evaluated for selectivity using 21 bacterial isolates and for plating efficiency using Xcm. The bacterial isolates included a soilborne Xanthomonas species and three pathogenic Xanthomonas strains that infect cassava, cabbage and beans. Although the plating efficiency of Xcm on CCA was lower (59%) than on non-selective yeast extract peptone glucose agar (YPGA), its selectivity was significantly higher, averaging 60 and 82%, when isolating from banana fruits and soil, respectively. CCA was also superior when isolating Xcm from insect vectors, with selectivity of 48–75%, compared with 8–17% on YPGA. Xanthomonas campestris pv. phaseoli did not grow on CCA, while X. campestris pv. campestris and X. axonopodis pv. manihotis grew, but their colonies were smaller than those of Xcm. Twenty-nine out of 33 suspected Xcm strains isolated from plants, soil and insects using CCA were pathogenic when inoculated onto banana plants, indicating that CCA can be a reliable tool in isolating Xcm populations. The medium should prove useful in studies on ecology, epidemiology and management of the banana bacterial wilt pathogen that is currently ravaging bananas in East and Central Africa

Identification of Xanthomonas vasicola (formerly X. campestris pv. musacearum), causative organism of banana xanthomonas wilt, in Tanzania, Kenya and Burundi

Article purchased; Published online: 28 Feb 2010Xanthomonas campestris pv. musacearum (Xcm) causes a disease onbanana (Musa spp.) and enset (Ensete spp.) known as banana xanthomonaswilt (BXW). Recent studies have shown that Xcm is a strain of X. vasicola(Aritua et al., 2008). However, the status of pathovars within thespecies remains unclear. Prior to its discovery in Uganda in October 2001,the disease had been limited to Ethiopia (first reported 1968). Since thenthe disease has spread to the Democratic Republic of Congo and Rwanda(observed in May 2004 and September 2005 respectively). BXW cancause high yield losses and is a high priority concern within the GreatLakes region. A comprehensive review of the pathogen and diseasewas recently published by Smith et al. (2008). Thus far, outbreaks inTanzania, Kenya and Burundi have only been referred to in symposiumproceedings and on various websites. These new records are thus officiallyreported here for the first time.In Tanzania, the disease was first reported in the Kagera region of northwest Tanzania, bordering Lake Victoria, Uganda, Rwanda and Burundi,in September 2005 (Mgenzi et al., 2006). Spread has continued, but not toother major banana growing areas. In Kenya, the disease was firstreported in September 2006 in the Teso District, of western Kenya,bordering Uganda (Anon, 2006). Spread has since been reported as slow.In Burundi the disease was first observed during October 2006 (Anon.,2006). The current status of BXW in Burundi is unclear with no recentsubstantiated reports.Bacterial cultures were isolated from diseased racemes from Tanzaniaand Burundi at CABI, UK and from Kenya at KARI (NARL). All cultureswere identified to species level at FERA by fatty acid profiling (MIDI system)and DNA analysis using X. vasicola specific primers (Aritua et al.,unpublished data) and partial sequencing of the gyrase B gene (Parkinsonet al., 2007). Koch’s postulates were fulfilled for all strains at FERA bystem inoculation of banana plants (height approximately 30 cm) with abacterial suspension (200 lL with ~107 cfu ⁄ mL) under controlled environmentalconditions (minimum temperature 27ºC). Identification ofXcm isolates from Burundi and Kenya was further supported by OhioState University and KARI, respectively, using X. vasicola specific primers(Lewis-Levy Miller, unpublished data) that have a different target site tothose of Aritua et al. (unpublished data).Reference cultures are held by the UK National Collection of PlantPathogenic Bacteria, Accession Nos. NCPPB 4392-5 (Tanzania), 4434(Kenya) and 4433 (Burundi)