Distribution Pattern of Root Nodules in Relation to Root Architecture in Two Leading Cultivars of Peanut (Arachis hypogaea L.) in Japan

Abstract

To effectively utilize symbiotic nitrogen fixation, we examined the formation of root nodules along with root system development in two leading peanut cultivars in Japan, Chibahandachi and Nakateyutaka. Differences in the number, size and distribution pattern of root nodules between the two cultivars are discussed in relation to their root architecture. Many root nodules are formed on the 1st-order lateral roots in the peanut. The difference between the two cultivars in the number of nodules on the 1st–order lateral roots and the diameter of the 1st-order lateral roots at the basal part of the taproot increased during secondary thickening period. Those changes were significantly greater in Chibahandachi than in Nakateyutaka at later growth stages. Chibahandachi had fewer, but larger nodules than those in Nakateyutaka. In Nakateyutaka, a larger number of new nodules were formed on the lateral roots at the middle part of the taproot than in Chibahandachi. This suggests that in Chibahandachi nodules grow for a longer period during plant growth, and in Nakateyutaka new nodules are formed even at late stages of plant growth. In addition, there appears to be an optimal diameter of the 1st-order lateral roots for nodulation at each growth stage.