Isolation of Plant-growth Promoting Bacteria from Fumigated Soils

Soil fumigation induces an ‘increased growth response’ (IGR) in crops of about 35%, even in soils with low pathogen and weed pressures (1). Populations of Pseudomonads and other bacteria increase in fumigated soils as soon as 2-wks after treatment (2). Some Pseudomonads can stimulate plant yields through the production of siderophores, growth promoting substances and by the suppression of soil-borne pathogens. Therefore, researchers have hypothesized that an increase in plant-growth promoting Pseudomonads in fumigated soils may partly cause the IGR of crops (e.g. 3). This preliminary study examined this hypothesis by: (a) monitoring the changes in Pseudomonads that occur after soil fumigation, and (b) isolating plantgrowth promoting Pseudomonads from fumigated soils.