Sponsored by the APS Biological Control Committee1998 Annual Meeting – Las VegasBallroom C – 1-5 PM Monday, Nov. 91:00PM
Burkholderia cepacia is efficaceous for control of several soilborne disease problems. It has been successfully used for control of major soilborne disease problems caused by Pythium spp., Rhizoctonia solani, Fusarium spp., and others. Disease control has been demonstrated experimentally with B. cepacia for the past 25 years and was recently successfully registered with EPA and commercially developed. No adverse effects caused by B. cepacia have been reported during this long period of experimental and commercial use.
Recent taxonomic studies indicated that there is a marked heterogeneity amongst strains routinely identified as B. cepacia. Integrated genotypic and phenotypic analyses have shown that B. cepacia isolates, cultured from clinical or environmental sites, belong to at least five distinct genomic species or genomovars, referred to collectively as the B. cepacia complex. Following identification of distinguishing phenotypic characteristics, the name B. multivorans has been proposed for genomovar II, while genomovar V was identified as the recently described B. vietnamiensis, an organism thus far primarily isolated from the rice rhizosphere. The remaining three groups are referred to as B. cepacia genomovars I, III and IV pending differential phenotypic tests. All five groups and other Burkholderia species such as B. gladioli have been cultured from CF patients and environmental samples. A variety of species, some of which represent novel taxa, are regularly misidentified as B. cepacia; similarly, B. cepacia strains are regularly not recognized as Burkholderia strains.
More than thirty B. cepacia isolates, including representatives of all five of the genomovars defined by Vandamme et al, contained between two and four replicons with sizes in the range of 1 to 4 Mb. Analysis of spontaneous and transposon-generated mutants has revealed an underlying high frequency of genomic rearrangements which may complicate genetic analysis of B. cepacia. Click here for table showing size and number of replicons in B. cepacia isolates.
Microbial pesticides, live and killed microbes sold to control pests, are registered by EPA’s Biopesticide and Pollution Prevention Division. Registration is undertaken to assure that regulated pest control products do not present unreasonable risks to those who may be exposed to them. This process typically includes toxicology tests performed on animals as surrogates for human risk. Toxicological tests are also typically performed on non-target plants and animals to assess risk to the environment. Unlike traditional pesticides, toxicology tests required for microbial pesticides are usually limited to short term high dose exposure, also known as acute tests. Also unlike traditional pesticides, pathogenicity must be assessed in the case of live microbial pesticides. Scientific literature may be used in the risk evaluation process where appropriate, and some tests may be waived if there is sufficient evidence that they are not necessary. One important aspect of the evaluation of microbial pesticides is the taxonomic relationship between known human, plant, or animal pathogens or toxin producers and the microbe being considered for registration. The taxonomic relationship between known human pathogenic and biocontrol strains of B. cepacia has become particularly important.
RETURN TO APSnet FEATURE STORY