INFLUENCE OF PLANT DEVELOPMENT, CULTIVAR AND SOIL TYPE ON MICROBIAL COLONIZATION OF MAIZE ROOTS

An understanding of the environmental factors affecting size and compo sition of rhizosphere microbial populations is important when introduc ing exogenous microorganisms in the rhizosphere of crop plants for pla nt growth promotion. The influence of plant development, cultivar and soil characteristics on the total rhizosphere microbial population and community structure of maize planta was investigated using the concep t of r/K strategy. During maize growth microbial population density di d not vary significantly, whereas the microbial community structure ch anged markedly in the early stages of plant growth but afterwards rema ined stable. Comparisons of the rhizosphere microflora of several maiz e cultivars, showing differential susceptibility to Fusarium, revealed that different cultivars support similar numbers of indigenous bacter ia. Moreover the bacterial community structures of different maize cul tivars did not show any significant difference. On the contrary, soil type had a marked influence on the microbial population of maize rhizo sphere. Indeed the rhizosphere microbial density and community structu re varied significantly among the different sampling sites. In conclus ion, plant development and soil type have a marked influence on the rh izosphere microflora of maize, whereas cultivar type does not have a r ole. (C) 1998 Elsevier Science B.V. All rights reserved.