Detection of Cassava Blight Bacteria from Leaf and Soil

Abstract

Detection of Xanthomonas campestris pv. manihotis (Xcm) causing cassava blight by the method of indirect immunofluorescent staining (IF) using antiserum produced in New Zealand White rabbit against membrane protein complex (MPC) of Xcm can be done at the minimum of 10² cells/cm² of leaf and 10³ cfu/g of amended soil. A semiselective SXM medium was developed for detection of Xcm containing (g/l) : K₂HPO₄ 0.8, KH₂PO₄ 0.6, yeast extract 0.7, soluble starch 8.0, glucose 1, agar 15, methyl green 0.01, methyl violet 2B 0.001, cephalexin 0.01, gentamicin sulfate 0.001, and cycloheximide 0.25. The medium showed 90-100% inhibition of soil saprophytes and can be used to detect Xcm from soil and leaf at the minimum of 10³ cfu/g of soil and 10² cells/cm² of leaf, respectively. This experiment was the first report to demondtrate the use of IF and semiselective medium for detection of Xcm from leaf and soil. Efficiency in detection of the two methods was nearly the same in which either con be chosen when appropriated especially for epidemiological study.