Isolation and identification of Ammodendron bifolium endophytic bacteria and the action mechanism of selected isolates-i
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ORIGINAL PAPER
Isolation and identification of Ammodendron bifolium endophytic bacteria and the action mechanism of selected isolates-induced seed germination and their effects on host osmotic-stress tolerance Yanlei Zhu1,2 Received: 9 June 2018 / Revised: 20 September 2018 / Accepted: 28 September 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract This study aimed to identify Ammodendron bifolium endophytic bacteria, and to evaluate promoting mechanism of selected isolates on seed germination and their effects on host osmotic-stress tolerance. Forty-five strains were isolated from A. bifolium and were classified into 13 different genera by 16S rDNA gene sequence analysis. AY3, AY9 and AG18, which were identified as Staphylococcus, Kocuria, Bacillus sp., promoted host seed ethylene release during germination. Ethrel and 1-aminocyclopropane-1-carboxylic acid (ACC) imitated the effect of AY3, AY9 and AG18 on seed germination. The data suggest that ethylene mediates AY3-, AY9-, AG18-induced A. bifolium seed germination. In addition, osmotic stress prevented seed germination and radicle elongation. However, the inhibitory effect of osmotic stress on seed germination and radicle elongation were rescued by AY3, AY9 and AG18. The results show that AY3, AY9 and AG18 increased osmotic-stress tolerance in A. bifolium. AY3, AY9, AG18 induced A. bifolium seed germination through promoting ethylene production during endophytic bacteria–plant interaction, and increase osmotic-stress tolerance in A. bifolium. AY3, AY9 and AG18 are potential candidates for the protection of A. bifolium. Keywords Ammodendron bifolium · Endophytic bacteria · Ethylene production · Seed germination · Osmotic-stress tolerance
Introduction Endophytic bacteria are a class of microbes that colonize the interior tissues of plant without causing harm to their host (Hallmann et al. 1997). These microbes and their host have formed a harmonious association by establishing symbiotic, mutualistic, commensalistic, and trophobiotic relationships (Ryan et al. 2008; Nair and Padmavathy 2014). Numerous reports have shown that bacterial endophytes promote host plant growth by synthesizing phytohormones (Sgroy et al. 2009; Chen et al. 2010; Luo et al. 2012), fixing atmospheric nitrogen (Hurek et al. 2002; Iniguez et al. 2004; Ji et al. Communicated by Erko Stackebrandt. * Yanlei Zhu [email protected] 1
College of Life Sciences, Xinjiang Normal University, Urumqi 830054, Xinjiang, China
College of Life Sciences, Shaanxi Normal University, Xi’an 710119, Shaanxi, China
2
2014; De Jesus Santos et al. 2014), enhancing phosphate solubilization activity (Verma et al. 2001; Yu et al. 2011) or improving the availability of iron (Yaish et al. 2015). They have also been known to suppress bacterial (Van Buren et al. 1993) and fungal (Hinton and Bacon 1995) pathogens, induce systemic resistance (M’piga et al. 1997), and control plant-parasitic nematodes (Kerry 2000) and insects (Azevedo et al. 2000), which make them suitable as biocontrol a
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