Pathogen

Xanthomonas axonopodis pv. phaseoli

Overview

Scientific name	Xanthomonas axonopodis pv. phaseoli
Genus	Xanthomonas
EPPO code	XANTPH
Common name	Common Bacterial Blight of Bean
Synonyms	Pseudomonas phaseoli

Description

From ISTA method 7-021:

AFter 4-5 days on MT, Xap colonies are yellow distinguished by two zones of hydrolysis; a large clear zone of casein hydrolysis and a smaller milky zone of Tween 80 lysis. The fuscans of XAP colonies produce a brown diffusible pigment. If not visible after 4 days, incubate for an additional day. Often the fuscans type colonies show Tween 80 lysis.The colony size and colour can differ within a sample.

After 4-5 days on XCP1, Xap colonies are yellow, glistening and surrounded by a clear zone of starch hydrolysis. The fuscans of Xap colonies produce a brown diffusible pigment after 5 days of incubation. Often the fuscans type colonies show Tween 80 lysis. The colony size and colour can differ within a sample.

Suspected colonies, when subcultured on YDC, will be yellow and mucoid in appearance.

Pathogenicity test should be done on a bean seedling of a cultivar known to be susceptible to all races of Xap (e.g. Michelet or Contender at 20-30C) until the fist leaf is just visible. After innoculation, typical symptoms include dark green water-soaked lesions at the point of entry. Lesions can become red-brown, elongate extending into the stem causing slight to severe stem cracking. Symptoms for fuscans and non-fuscans are the same.