Rhizosphere colonization pattern of Agrobacterium radiobacter strain G12A, an antagonistic rhizobacterium to the potato cyst nematode Globodera pallida

Abstract

The colonizing behaviour and survival of the rhizosphere bacterium Agrobacterium radiobacter G12A, an effective antagonist of the potato cyst nematode Globodera pallida, was investigated at the soil-root interface. A rifampicin resistant mutant that was used for reisolation after spray application onto tuber pieces, was quantitatively recovered 7, 14, 21, and 56 days after planting from the rhizosphere, rhizoplane, root tip, stem base, the initial tuber piece and from root-free soil mix. After 21 days A. radiobacter G12A constituted 10 to 30% of the total numbers of detectable bacteria on potato tubers and in the rhizosphere. Feeding groups of rhizoplane-colonizing microorganisms increased in density after the introduction of A. radiobacter G12A at 15 and 20 °C, but not significantly. All groups of microorganisms tested (except flourescent Pseudomonads at 25 °C) increased in the potato rhizoplane, some of them significantly, when temperature was increased from 15 °C to 25 °C.