Differential response of soybean (Glycine max (L.) Merr.) genotypes to lipo-chito-oligosaccharide Nod Bj V (C(18:1) MeFuc)

Lipo-chito-oligosaccharides (LCOs) are bacteria-to-plant signal molecules essential for the establishment of rhizobia-legume symbioses. LCOs invoke a number of physiological changes in the host plants, such as root hair deformation, cortical cell division and ontogeny of complete nodule structures. The responses of five soybean cultivars to Nod BJ: V (C(18:1) MeFuc) isolated from Bradyrhizobium japonicum strain 532C were studied with a new technique. Two distinct types of root hair deformation were evident (i) bulging, in which root hairs were swollen at the tip or at the base depending on the cultivars and (ii) curling. The nodulating capacity of B. japonicum 532C varied among cultivars. Cultivars that produced a bulging reaction when treated with LCO had fewer nodules and the roots had low phenol contents. Cultivars that produced curling had higher numbers of nodules and the roots had higher amounts of phenol. Further, the roots of cultivars that showed root hair bulging were able to degrade LCO much faster than cultivars that manifested curling. The results of the present study establish relationships among the type of LCO-induced root hair deformation, root system LCO-degrading ability and nodulation capacity of soybean cultivars.