The Effect of Ultra Violet Light on the Symbiotic Effectiveness and Some Physiological Characteristics of Four Strains of Rhiozobium trifoli

S ummary . UV light was used to induce mutations in 4 strains of Rhizobium trifolii. Mutations were found with modified acid production, generation time, polysaccharide production and symbiotic effectiveness on S184 white clover. Of 72 mutants examined, one was more effective than the parent, 9 had either similar or reduced effectiveness compared with their parental strains and the remainder were non-infective. A significant correlation ( P <0·05) was found between the effectiveness of the strains and their acid production on an agar medium but no such relationship was found in liquid medium. No other relationships were found between any of the physiological or symbiotic characteristics examined.