ROOT EXUDATION IN COWPEA AND SORGHUM AND THE EFFECT ON SPORE GERMINATION AND GROWTH OF SOME SOIL FUSARIA.

Exudation patterns in cowpea and sorghum seed and seedlings were studied using a filter paper technique. Profuse exudation was observed from cowpea seeds but this decreased considerably 2 days after germination. Root tips of primary, lateral, and adventitious roots were found to be the major sites of exudation but the older parts of seedling roots also exuded significant quantities of amino acids. Exudates from the roots of both species enhanced the germination of conidia of four Fusarium species previously isolated from the rhizosphere and rhizoplane. The germ tubes and some conidia were lysed by cowpea exudate in 48 h. Mycelial growth in liquid culture was enhanced in cowpea root exudate medium but was scanty in sorghum exudate; the presence of antifungal substance was suspected in the latter. The significance of the results obtained in relation to microbial root colonization and pathogenesis is discussed. [ABSTRACT FROM AUTHOR]