Diversity and Plant Growth Promoting Ability of Culturable Endophytic Bacteria in Nepalese Sweet Potato

Abstract

There is no information on Nepalese sweet potato endophytes. We isolated 243 endophytic bacteria belonging to 34 genera in six classes from 12 locations of Nepal. Among them, the predominant classes were Bacilli and Gammaproteobacteria. The principal component analysis revealed that the composition of bacterial classes was unrelated to the environmental parameters of the sampling sites. Regarding their plant growth promoting potentials, 57% of the strains demonstrated indole-3-acetic acid (IAA) producing ability while 5% strains had nitrogen fixing gene (nifH) and acetylene reduction assay (ARA) activity. The representative strains in all six classes showed antagonistic effect against bacterial pathogens while only Bacillus strain showed the effect against fungal pathogen. For endophytic traits, cellulase activity was observed in 5 classes, while pectinase activity was only in Proteobacteria. Fresh weight and vine length of sweet potato increased by inoculating mixed cultures of the isolates from each location.

Nodulation and Agronomic Performance of Indigenous Rhizobia Isolated from Bambara Groundnut (Vigna Subterranean L.) Nodules in Dalao, Côte d’Ivoire

“…In fact, soil bacteria collectively called rhizobia can enter into a symbiotic association with vegetables especially Bambara groundnut which leads to the formation of nitrogen fixing root nodules. This symbiotic interaction is of agronomic and ecological importance due to its high nitrogen content in the total nitrogen balance of terrestrial ecosystems [5]. In addition, the soil bacteria belonging to the symbiotic and endophytic bacteria are well known for their beneficial implications to promote directly the growth and indirectly the defense of plants [6;7].…”

Plant Growth Promoting Effects of Nepalese Sweet Potato Endophytes

“…Sal 3 colonized the rhizosphere and tissues of tomato when seed was inoculated at higher levels. Their cellullase-and pectinase-producing properties [15] might help them enter into the plant tissue. Hydrolytic enzymes at the infection site leads to cell wall degradation and entry of bacteria such as Rhizobium and Azospirillum strains in white clover [31].…”

“…Strains used in this study were isolated from Nepalese sweet potato tubers [15]. Eight sweet potato endophytes from the Salyan location were used in this study (Table 1).…”

“…Sal 1 and Herbaspirillum sp. Sal 6, which were reported to have the nif H gene [15], the acetylene reduction assay (ARA) was conducted. Cell suspensions of the isolates were prepared at 10 9 CFU/mL after 2 days of culture in liquid MR medium and then washed twice with autoclaved distilled water by centrifugation (at 10,000 rpm at 4 • C for 10 min).…”

“…Venkatachalam et al [14] reported a diverse bacterial community in temperate soils of Nepal with different enzymatic activities. In our previous study, we reported diverse genotypes of sweet potato bacterial endophytes in 12 different locations in Nepal, and the inoculation of mixed cultures of the strains from each location improved the fresh weight and vine length of sweet potato in growth chambers [15]. In this study, the endophytes from the 'Salyan' location were selected based on their physiological and plant growth-promoting properties to identify endophytes that can promote plant growth.…”