A new selective medium for <i>Burkholderia caryophylli</i> , the causal agent of carnation bacterial wilt

Abstract

A new selective medium (APCA medium) was developed for the isolation of Burkholderia caryophylli , the causal agent of carnation bacterial wilt, from both plants and soil. The optimal concentration and combination of antibiotics was investigated to determine the most selective condition for growing B . caryophylli . The resultant composition of the medium per litre was: 0·79 g (NH 4 ) 2 SO 4 , 1·0 g KH 2 PO 4 , 0·5 g MgSO 4 · 7H 2 O, 0·2 g KCl, 2·0 g D‐arabinose, 5 mg crystal violet, 50 mg cycloheximide, 50 mg polymyxin B sulphate, 50 mg ampicillin sodium, 10 mg chloramphenicol, 25 mg blue tetrazolium, and 15 g agar. Plating efficiency ranged from 119 to 174% with an average of 141% compared to that of nutrient agar. The bacterium was successfully isolated from contaminated soil and plant tissues with this medium. Moreover, the medium almost completely inhibited the growth of other plant pathogenic bacteria and soil saprophytes. This selectivity was high enough to detect B . caryophylli in contaminated soil.