Population of Diazotrophic Endophytes in Stem Apoplast Solution of Sugarcane and Related Grass Species in Tanegashima, Japan

We collected stem samples from sugarcane germplasm of wildtype (43 clones of Saccharum spontaneum and S. robustum), cultivated (34 clones of S. hybrid spp., S. sinense, and S. barberi), and related grass species (7 clones of Erianthus arundinaceus, Miscanthus floridulus, and Ripidium sp.) to survey the colonization and population of diazotrophic endophytes in apoplast solution. Using the acetylene reduction assay-most probable number (ARA-MPN) method, 11 clones of wildtype species, nine clones of cultivated species, and three clones of related grass species were colonized by diazotrophic endophytes. The population density of diazotrophic endophytes in all ARA-positive samples ranged from 102 to 108 cells mL-1 apoplast solution and differed among clones and species. The results indicate a differential colonization and population of diazotrophic endophytes in stem apoplast solution.