Lactobacillus plantarum; a deleterious contaminant of plant tissue cultures

Abstract

Lactobacillus plantarum was isolated from in vitro plant cultures of Hemerocallis Stella d'ora, Catherine Woodbury and Stafford. Infected cultures deteriorated rapidly during three subcultures (15 weeks) when grown in vitro, showing chlorotic white shoots and grey calli. Weaned plants developed normally when transferred to the soil. The drop in multiplication rate of plant cultures coincided with a decrease in pH of the growth media. Uninfected plants of Hemerocallis Stella d'ora showed the same symptoms after inoculation with L. plantarum. Lactobacillus plantarum was reisolated from inoculated plant cultures that showed symptoms, thus fulfilling Koch's postulates. In plants inoculated with L. plantarum both the amount of dl‐lactic acid formed and the number of plants showing symptoms increased with increasing numbers of bacteria in the inoculum, wheras plant multiplication rate and pH decreased. These effects could be reproduced by adding dl‐lactic acid to the multiplication medium of plants free from L. plantarum, suggesting that the bacterial production of lactic acid was responsible for the changes in infected plants.

Effect of medium acidity on growth and rooting of different plant species growing in vitro

“…Shoots were grown in irradiated plastic (clear polystyrene K-resin) containers (6.5 cm high, 8 cm diameter) containing 50ml (+/-6ml) of medium (as described below) and unless stated otherwise 10 plant pieces were inoculated per culture vessel in all trials. Only shoots free of detectable microbial contaminants (those tested on specific media [see Leifert et al 1989 for the method used] for revealing bacterial contaminants) were used in experiments. During trials shoots were tested for the presence of detectable microbial contaminants at every subculture and shoot cultures that became contaminated were discarded since contaminants were shown to affect growth rates and to alter the medium pH (Leifert et al 1989(Leifert et al , 1991b.…”

Effect of combinations of antibiotics on micropropagated Clematis, Delphinium, Hosta, Iris and Photinia

“…Only index-negative shoots were used in experiments. During trials shoots were also indexed at every subculture and shoot cultures that became contaminated were discarded, since contaminants were shown to affect growth rates of tissue cultured shoots (Long et al 1988, Leifert et al 1989b.…”

Bacterial contaminants of micropropagated plant cultures

“…All Iris explants examined showed soft rot symptoms and subsequently died. Hemerocallis cultures infected with Lactobacillus plantarum often showed severe chlorosis of leafs, grey calli and plant death (Leifert et a/. 1989).…”