Factors Influencing the Distribution, Growth and Infectivity of Casuarina-Infective Frankia

Abstract

Further studies revealed that Casuarina cladodes increased the infectivity of a soil inoculum by a factor of 3.2, whereas leaves of a sympatric check plant, Terminalia catappa (Combretaceae), barely increased the same soil's infectivity. Charcoal and clay added to the seedling growth substrate to bind organic material significantly inhibited nodulation of C. cunninghamiana by a Frankia isolate, suggesting the host may release compounds necessary to the nodulation process. In a final study, the infectivity of soils inoculated with Frankia isolate CjI82001 decreased over time, whereas infectivity of soils without inoculum either increased or remained unaffected. A positive synergism was observed between the Frankia isolate and the soil biotic community, resulting in an increased infectivity of the Frankia isolate.