Nodulation and growth of yard long bean plants : The results showed that the control management subplots (added with nitrogen) gave no nodule at all whilst the rest produced some certain amounts of nodulation number, e.g. the non-managed subplots (no yard long bean plants) gave the mean value of nodule numbers of 3 whilst those plants with yard long bean cultivars had produced mean nodule numbers of 5 and 7 for white seeded and KKU25 cultivars, respectively. The differences were large and of statistical significance (table : 4). The results suggested that indigenous Rhizobium manifested some preferential symbiotic responses for their hosts, which KKU25 yard long bean plants had performed the highest quality and greater than that of the white seeded cultivar. Therefore, selective quality of Rhizobiumwith respect to host could possibly be the element for biologists to consider when Rhizobium technology must be applied within the range of field grown legume crops.