Recent studies have pointed out that legume nodules harbour a great diversity of endophytic bacteria other than rhizobia, collectively known as non-rhizobia endophytes (NRE). Few studies about their role and the factors driving the community assembly have been conducted, despite their potential as plant growth promoters (PGPs). The aim of this study was to explore the diversity of culturable endophytic communities of nodules and roots of hairy vetch (Vicia villosa Roth) plants, grown at different levels of phosphorus availability. We employed a combination of traditional isolation procedures and PCR-DGGE analyses to investigate the diversity of endophytes, and we performed in vitro and molecular assays to evaluate some PGP traits (phosphorus solubilization ability, hydrolytic enzymes production, N-fixation potential). Representative root and nodule endophytes were identified by 16S rRNA gene sequencing. Moreover, the NRE isolates were co-inoculated with Rhizobium leguminosarum in sterile seeds of hairy vetch to verify their proficiency in nodule colonisation. We obtained 17 isolates from nodules and 34 from roots, and we found a greater diversity in roots than in nodules. The endophytic populations in roots and nodules were different, and an influence of the phosphorus soil content in driving the composition of the endophytic communities was reported. According to the physiological tests, several root endophytes were phosphorus solubilizers and many were proteases productors, while only one strain of Bacillus aryabhattai showed these features among the nodule isolates. Interestingly, the same strain was the only nodule isolate able to recolonize vetch plants after inoculation. Overall, these results suggest that roots of hairy vetch may be more promising than nodule tissues as a source of potential PGPs, although species like B. aryabhattai, able to colonise both plant compartments, may also have a relevant role in growth promotion, and should therefore be studied in more detail within this system.
Culturable diversity of root and nodule endophytes from Vicia villosa plants grown at different levels of phosphorus availability
Mania Ilaria
First
;Martina Florian;Roberta GorraLast
2021-01-01
Abstract
Recent studies have pointed out that legume nodules harbour a great diversity of endophytic bacteria other than rhizobia, collectively known as non-rhizobia endophytes (NRE). Few studies about their role and the factors driving the community assembly have been conducted, despite their potential as plant growth promoters (PGPs). The aim of this study was to explore the diversity of culturable endophytic communities of nodules and roots of hairy vetch (Vicia villosa Roth) plants, grown at different levels of phosphorus availability. We employed a combination of traditional isolation procedures and PCR-DGGE analyses to investigate the diversity of endophytes, and we performed in vitro and molecular assays to evaluate some PGP traits (phosphorus solubilization ability, hydrolytic enzymes production, N-fixation potential). Representative root and nodule endophytes were identified by 16S rRNA gene sequencing. Moreover, the NRE isolates were co-inoculated with Rhizobium leguminosarum in sterile seeds of hairy vetch to verify their proficiency in nodule colonisation. We obtained 17 isolates from nodules and 34 from roots, and we found a greater diversity in roots than in nodules. The endophytic populations in roots and nodules were different, and an influence of the phosphorus soil content in driving the composition of the endophytic communities was reported. According to the physiological tests, several root endophytes were phosphorus solubilizers and many were proteases productors, while only one strain of Bacillus aryabhattai showed these features among the nodule isolates. Interestingly, the same strain was the only nodule isolate able to recolonize vetch plants after inoculation. Overall, these results suggest that roots of hairy vetch may be more promising than nodule tissues as a source of potential PGPs, although species like B. aryabhattai, able to colonise both plant compartments, may also have a relevant role in growth promotion, and should therefore be studied in more detail within this system.
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