Mediterranean Native Leguminous Plants: A Reservoir of Endophytic Bacteria with Potential to Enhance Chickpea Growth under Stress Conditions

Abstract

Bacterial endophytes, a subset of a plant’s microbiota, can facilitate plant growth by a number of different mechanisms. The aims of this study were to assess the diversity and functionality of endophytic bacterial strains from internal root tissues of native legume species grown in two distinct sites in South of Portugal and to evaluate their ability to promote plant growth. Here, 122 endophytic bacterial isolates were obtained from 12 different native legume species. Most of these bacteria possess at least one of the plant growth-promoting features tested in vitro, with indole acetic acid production being the most common feature among the isolates followed by the production of siderophores and inorganic phosphate solubilization. The results of in planta experiments revealed that co-inoculation of chickpea plants with specific endophytic bacteria along with N2-fixing symbionts significantly improved the total biomass of chickpea plants, in particular when these plants were grown under saline conditions. Altogether, this study revealed that Mediterranean native legume species are a reservoir of plant growth-promoting bacteria, that are also tolerant to salinity and to toxic levels of Mn. Thus, these bacterial endophytes are well adapted to common constraints present in soils of this region which constitutes important factors to consider in the development of bacterial inoculants for stressful conditions in the Mediterranean region.

Exogenous ACC Deaminase Is Key to Improving the Performance of Pasture Legume-Rhizobial Symbioses in the Presence of a High Manganese Concentration

“…Nevertheless, in both cases, the presence of the Q1 strain facilitated the formation of nodules by these rhizobial strains and led to an increase of the host's growth. These results are in agreement with previous reports showing that non-rhizobial bacteria stimulated legume growth and nodulation under different abiotic stress conditions, such as salinity [18,48,[53][54][55][56][57], toxicity of copper [58][59][60], Mn [18], cadmium [23,61], and zinc [60]; as well as under biotic stress, namely root rot caused by Fusarium solani [56]. On the other hand, no beneficial effects of the co-inoculation of non-rhizobial bacterium along with M. ciceri LMS-1 were observed with the chickpea plants grown either under non-stressed or stressed conditions.…”

“…As previously observed [18], and compared to non-stressed conditions, the root and shoot dry weights of chickpea plants grown under a high concentration of Mn were significantly reduced either when single inoculated with the highly efficient strain M. ciceri LMS-1 [29,30,34] or co-inoculated with LMS-1 and Q1 strains ( Figure 3). In fact, a statistically significant difference in average shoot and root dry weights by plant growth conditions was found (f(1) = 193.668, p < 0.001) for RDW and f(1) = 151.470, p < 0.001) for SDW).…”

“…The endophytic Pseudomonas sp. Q1, which was isolated from L. angustifolius L. roots and previously characterized [18], was selected to evaluate its effects on the symbiotic rhizobium-legume associations. Three rhizobial strains, namely M. ciceri LMS-1, R. leguminosarum bv.…”

Connecting the Lab and the Field: Genome Analysis of Phyllobacterium and Rhizobium Strains and Field Performance on Two Vegetable Crops

“…For this reason, in the past year, several research studies have evaluated ways of increasing plant growth by using bacterial endophytes isolated from non-legume plants [8,9] and from legume nodules [10][11][12][13][14][15][16][17][18]. These nodules contain the rhizobia responsible for their formation and for symbiotic nitrogen fixation as well as other bacterial endophytes with different plant growth promotion mechanisms [19][20][21][22].…”

Seed Dormancy Breaking and Germination in Bituminaria basaltica and B. bituminosa (Fabaceae)

“…In the Mediterranean region, natural pasture areas possess a considerable component of native legume species [ 1 ]. This is a very remarkable characteristic because these plants are both a source of highly nutritive natural forage, and an effective nitrogen fixation agent into the soil [ 2 ]. Therefore, an increasing interest is being given to the identification of new wild genetic resources within this plant family to be used as forage and for soil enrichment in marginal areas [ 3 ].…”