Nodule‐Like Structres Induced on Peanut by Chlorosis Producing Strains of Rhizobium Classified as R. Japonicum¹

Some strains of rhizobia produce a rhizobitoxine‐induced foliar chlorosis on soybean, Glycine max (L.) Merr., and have a limited ability to nodulate the nodulation restrictive genotype (rj 1 ). This study was undertaken to determine and compare the effect of chlorosisinducing or rj 1 ‐compatible strains and nonchlorosis‐inducing strains on another legume, peanut ( Arachis hypogaea L., cultivars ‘Starr’ and ‘Spancross’), in Leonard jar culture. Ten different rhizobial strains that induce chlorosis or nodulate rj 1 ‐plants, produced swellings at the nodulation sites on peanut roots. No rhizobial‐induced chlorosis symptoms developed on either peanut cultivar. Control peanut plants inoculated with six different nonchlorosis‐inducing strains of Rhizobium japonicum (Kirchner) Buchanan did not have swellings. The clustering of three distinctive characteristics, a) ability to nodule rj 1 plants, b) the propensity to produce rhizobitoxine‐induced chlorosis symptoms on soybean, and c) the ability to induce nodule‐like swellings on peanut roots, in a common population of rhizobia suggests that these rhizobia may represent a taxonomically distinct group. These strains appear defective in their symbioses with both soybean and peanut, suggesting that they may have a symbiotic homology for a legume host other than either soybean or peanut.