Soybean Response to Indigenous Rhizobia as Influenced by Cultivar Origin1

Many investigators believe that when grown for the first time, the soybean [Glycine max (L.) Merr.] nodulates poorly unless inoculated with Rhizobium japonicum. However, in Nigeria the cultivar ‘Malayan,’ which originated from Indonesia, has nodulated quite well with indigenous strains of Rhizobium. We chose cultivars originating from Southeast Asia and from the USA and compared parameters associated with effective nodulation when these cultivars were grown with and without inoculation with Rhizobium japonicum. Seed inoculation with Nitragin‐S inoculant did not significantly improve nodulation, growth, amino‐N stem exudate, and yield of the Southeast Asian cultivars Malayan, ‘Orba,’ and ‘TGm 686.’ In contrast, the American cultivars ‘TGm 294‐4‐2371,’ ‘Bossier,’ and ‘Jupiter’ nodulated poorly without inoculum, and showed increases in growth of 36 to 47% and seed yield of 40 to 97% when inoculated. However, the American cultivars generally have better agronomic characteristicsa and higher yield potential than the Southeast Asian cultivars. It is, therefore, important to combine the desirable characteristics of these two distinct groups of soybean cultivars in the breeding program to develop improved cultivars suitable for and adapted to tropical environments.