Opportunities and constraints in the adaptation of technology for the diagnosis of bacterial plant diseases — experience from Tanzania*

Abstract

In order to improve diagnostic services and plant quarantine capabilities in Tanzania, the techniques of semi-selective media, the BACTID system, metabolic profiling (Biolog), indirect enzyme-linked immunosorbent assays (ELISA) and polymerase chain reaction (PCR) were assessed for suitability with the existing facilities for the diagnosis and detection of plantpathogenic bacteria of vegetables. Field-collected samples as well as farmers' own and commercial germplasm were used in studies involving Ralstonia solanacearum, Clavibacter michiganensis subsp. michiganensis and Xunthomonas campestris pv. vesicatoria in Solanaceae and X . c. pv. cumpestris in Brussicaceae. Each of the techniques was used successfully with one or more of the target pathogens; each had advantages depending on the speed, sensitivity and specificity required, as well as the costs of carrying out the diagnosis. However, constraints emerged relating to the use and disposal of materials such as plastic Petri dishes and toxic substances. The more familiar underlying constraints of high cost and poor availability of consumables and erratic water and electricity supply continued to present problems. These problems will be discussed in relation to the development of an integrated and sustainable approach to the provision of routine diagnostic services.

Field evaluation for resistance to the black rot pathogen Xanthomonas campestris pv. campestris in cabbage (Brassica oleracea)

“…The most economically important hosts of Xcc are the cole crops, forms of the polymorphic species Brassica oleracea (including cabbage, cauliflower, broccoli, Brussels sprouts, and kale) (Rubatzky and Yamaguchi, 1997), but Xcc is also reported on a number of other cruciferous crops, weeds, and ornamentals (Bradbury, 1986). Black rot has been reported as a major constraint in cabbage production in several countries including Nepal (Adhikari and Basnyat, 1999), Tanzania (Black et al, 2000;Massomo et al, 2003), Zimbabwe (Mguni et al, 1999) and in cauliflower production in India (Sharma et al, 1977;Sharma et al, 1995). In Tanzania, black rot is widespread in most of the cabbage growing areas, especially during the rainy seasons (Mgonja and Swai, 1998), where individual fields may succumb to heavy crop losses.…”