Jacobus Johannes Marion Meyer
University of Pretoria, South Africa
Title: The role of plant growth promoting microbes in the maintenance of the mysterious fairy circles of Namibia
Biography
Biography: Jacobus Johannes Marion Meyer
Abstract
The cause and maintenance of the hundreds of thousands of fairy circles in the Namibian pro-desert have not yet been
satisfactorily explained. Several diverse hypotheses have been put forward, but none have universally been accepted. We
previously found the ‘chemical footprints’ of toxic Euphorbia plants with GCMS analysis in nearly all the fairy circles of the
Garub region of Namibia. Th is implies that these toxic Euphorbia species were present, where there are fairy circles today. In
our search for the mechanism by which these toxic plants cause and maintain the fairy circles, we found that the E. damarana
extract has extremely low MIC values against plant growth promoting bacteria isolated from the ‘healthy’ soil from outside the
fairy circles. Th is indicates that the grasses will not have the benefi ts of plant growth promoting organisms when colonizing areas
where Euphorbia species have died in the harsh conditions of the Namib Desert. Th e MIC values of this extract were also found
to be very low against several human pathogenic bacteria. Pot experiments have shown that an inoculum of the rhizosphere
from grasses growing outside the fairy circles could reverse the negative eff ect of the fairy circle soil. Th is study supports the
hypothesis that the fairy circles are caused by Euphorbia spp. and maintained by the lack of plant growth promoting organisms.