No abstract

The influence of chitosaccharides on the symbiotic interaction between Bradyrhizobium and soybean was examined. The results show that chitosaccharides either positively or negatively affect soybean nodulation or plant growth depending on their molecular weight, concentration and the application methods. When directly added to the in vitro culture media, chitosan of high molecular weight inhibit Bradyrhizobium viability in a dose dependent manner while chitooligosaccharides reduce slightly the bacteria viability only at concentration equal or higher than 50 mg•L −1. Chitooligosaccharides significantly enhance nodule formation and dry mass in soybean roots at doses between 10 and 100 mg•L −1. Both types of chitosaccharides, at the highest doses (>500 mg•L −1), negatively affect plant height and root size, whereas medium doses (50 to 100 mg•L −1) increase slightly leave number. Under field conditions, foliar application of both chitosaccharides enhances growth and nodulation of soybean plants. Nevertheless, using this application method, chitosan remains more effective than chitooligosaccharides.