Symbiotic performance of several leguminous plants with legume nodule bacteria isolated from siratro (Macroptilium atropurpureum) at Mount Merapi Eruption, Indonesia

Abstract

Legume nodule bacteria (LNB) have the host specific nodulation in forming a symbiosis with leguminous plants. This research was conducted to investigate the symbiotic performance of 27 LNB isolates from Siratro (Macroptilium atropurpureum) at Mount Merapi Eruption, Indonesia with six legumes species such as Medicago sativa, Pisum sativum, Phaseolus vulgaris, Glycine max, Arachis hypogeal and M. atropurpureum. The successful cross inoculation group of LNB were further identified phenotypically. This research was designed with a completely randomized design using plastic pouch method for analyzing their symbiotic performance with three replications. The symbiotic relationship with those leguminous plants species were observed by the root nodule formations. The results revealed significant the root nodule formations in G. max which inoculating of each 4 isolates (MPB8, MPB9, MPB25 and MPB27), whereas the successful root nodule formation of M. atropurpureum was only observed which inoculating of MPB25 isolate. Furthermore, acetylene reduction assay of M. atropurpureum root nodules which inoculating MPB25 isolate showed the highest nitrogenase activity (0.0087 mmol N2 g-1 hour−1). In contrast, the lowest nitrogenase activity was measured at G. max nodules which inoculated by MPB25 isolate (0.0004 mmol N2 g-1 hour-1). Those nodule diameter results showed positive correlation significantly between fresh weight (r= 0.9) and dry weight of their nodules (r= 0.8), while nitrogenase activity showed negatively correlation between nodule diameter (r=-0.6), nodule number (r=-0.3) and fresh weight of nodule(r=- 0.7). Based on the phenotypic characterization, MPB8 and MPB9 isolates were identified genus Rhizobium, whereas MPB25 and MPB27 isolates were identified genus Ensifer.