ASSOCIATIONS OF BACTERIAL ENDOPHYTE POPULATIONS FROM RED-CLOVER AND POTATO CROPS WITH POTENTIAL FOR BENEFICIAL ALLELOPATHY

Clover and potatoes, in a crop rotation, were found to share specific associations of bacterial endophytes. Twenty-five bacterial species fr om 18 genera were common to both clover and potatoes and represented 7 3% of all the bacteria recovered from clover root tissues and 73% of a ll the bacteria recovered from potato tubers. Endophytic bacteria test ed in potato plant bioassays were predominantly plant growth neutral ( 56%). The remainder were either plant growth promoting (21%) or plant growth inhibiting (24%)(P < 0.05). Of the plant growth promoting bacte ria, 63% increased shoot height, 66% increased shoot wet weight, and 5 5% increased root wet weight. The effects of plant growth inhibiting b acteria were restricted to reductions in plant height (86%) and shoot wet weight (36%); root weight was not affected. Of the bacteria tested , 74% showed some degree of in vitro antibiosis to the clover and pota to pathogen Rhizoctonia solani. Such endophytic intercrop bacterial as sociations appear to be complementary in nature and support the view t hat there are microbial benefits to be gained from clover in crop sequ ences with potatoes, beyond those of the residual nitrogen left in the soil and the organic matter added.