Influence of plant development, cultivar and soil type on microbial colonization of maize roots

An understanding of the environmental factors affecting size and composition of rhizosphere microbial populations is important when introducing exogenous microorganisms in the rhizosphere of crop plants for plant 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 concept of r/K strategy. During maize growth microbial population density did not vary significantly, whereas the microbial community structure changed markedly in the early stages of plant growth but afterwards remained stable. Comparisons of the rhizosphere microflora of several maize cultivars, showing differential susceptibility to Fusarium, revealed that different cultivars support similar numbers of indigenous bacteria. Moreover the bacterial community structures of different maize cultivars did not show any significant difference. On the contrary, soil type had a marked influence on the microbial population of maize rhizosphere. Indeed the rhizosphere microbial density and community structure varied significantly among the different sampling sites. In conclusion, plant development and soil type have a marked influence on the rhizosphere microflora of maize, whereas cultivar type does not have a role. (C) 1998 Elsevier Science B.V. All rights reserved.