Endophytic bacteria of red clover as agents of allelopathic clover-maize syndromes

The early growth effects of red clover endophytic bacteria on maize seedlings were examined in greenhouse trials. We found that endophytic bacteria from preceding clover (Trifolium pratense L.) crops can be causal agents of the inhibitory allelopathic ‘clover-maize syndrome’. The effect was shown to be both direct (as in imbibition studies with bacterial suspensions of individual isolates) and indirect (as in leachate studies). Imbibition or watering with the crude leachate (leachate plus microorganisms) as opposed to filtered leachate (leachate minus microorganisms) derived from soil in which clover had been growing, prompted a reduction in the rate of emergence and growth of maize seedlings (Zea mays L.) but not germination percentage. It is concluded that the inhibitory allelopathic response in clover-maize sequences is a side-effect of the competition between bacteria for the same ecological niche which usually results in temporary growth retardation.