Biol Fertil Soils (2016) 52:53–64 DOI 10.1007/s00374-015-1052-x ORIGINAL PAPER Assessment of the potential role of Streptomyces strains in the revegetation of semiarid sites: the relative incidence of strain origin and plantation site on plant performance and soil quality indicators Carmen Mengual1 & Mauricio Schoebitz2 & Fuensanta Caravaca1 & Antonio Roldán1 Received: 2 June 2015 /Revised: 27 July 2015 /Accepted: 19 August 2015 /Published online: 4 September 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract We performed a field assay to assess the efficacy of Keywords Actinobacteria .Allochthonousstrain .Enzymatic strains of actinobacteria belonging to the Streptomyces genus, activities . Mediterranean native shrub . Native strain . isolated from two Mediterranean semiarid sites (Rellano and Revegetation Calblanque) with different soil characteristics, with regard to the establishment of Rhamnus lycioides L. seedlings in both locations, as well as their effect on soil chemical and microbi- Introduction ological properties 1 year after planting. At the Calblanque site, the inoculation with native strains was more effective Natural revegetation tends to be slow in arid and semiarid than that with allochthonous strains, with respect to increasing Mediterranean ecosystems, where the scarcity of water fre- shoot dry weight (about 48 and 28 %, respectively, compared quently limits plant establishment and growth (Caravaca to control plants), primarily due to improvements in NPK et al. 2005a; Schoebitz et al. 2014). However, other environ- uptake and plant drought tolerance. However, at Rellano, the mental factors also could provoke major differences in the efficacy of plant growth promotion was not influenced by the plant cover regeneration, including soil type and soil nutrient strain origin. The highest increases in the urease, protease, and availability (Alegre et al. 2004;Caravacaetal.2002). Several dehydrogenase activities and in microbial biomass C in re- revegetation programs have been developed by using a plant sponse to inoculation with actinobacteria occurred at the cover based on autochthonous plant species, which seems the Rellano site (about 200, 28, 29, and 30 %, respectively, com- most appropriate strategy for reclaiming degraded lands pared to the respective controls), regardless of the origin of the (Caravaca et al. 2005a). The use of shrubs to recover dry areas strain assayed. Strain origin and the biological fertility of the has been encouraged by the Common Agricultural Policy of plantation site should be considered in the selection of strains the European Union. The application of plant growth promot- of actinobacteria for use in the revegetation with shrub species ing microorganisms has been recorded as a successful tool in in semiarid environments. the reclamation of semiarid Mediterranean areas (Mengual et al. 2014; Schoebitz et al. 2014). Revegetation practices based on microbial inoculations require the development of an inoculum whose performance is optimum under specific environmental conditions (Bashan et al. 2014; Caravaca et al. 2003) in order to benefit the growth, nutrient uptake, and * Carmen Mengual hydric status of the host plant (Ortiz et al. 2014). Cell immo- [email protected] bilization is another biotechnological approach actively used in preparation and formulation of biofertilizers with partly 1 Department of Soil and Water Conservation, CSIC—Centro de unexploited potential (Vassilev et al. 2015)mainlyinagricul- Edafología y Biología Aplicada del Segura, P.O. Box 164, Campus tural and environmental applications where the use of poly- de Espinardo, 30100 Murcia, Spain saccharide beads catching PGPR offers a great protection to 2 Department of Soils and Natural Resources, Faculty of Agronomy, cells against biotic and abiotic stresses (Vassilev et al. 2012, University of Concepción, Casilla 160-C, Concepción, Chile 2015). Plants and microorganisms co-existing in a soil are 54 Biol Fertil Soils (2016) 52:53–64 often adapted to the same environmental conditions; so, pre- whether the actinobacterial strains stimulate plant growth di- sumably, native strains could be more effective for this pur- rectly or indirectly, by improving soil properties. To address pose in semiarid Mediterranean sites (Armada et al. 2014), these questions, we assessed, in a field experiment, the effica- allowing the local biodiversity to be preserved without intro- cy of actinobacterial strains isolated from two Mediterranean ducing new microbial species (Ortiz et al. 2014). semiarid sites with different soil characteristics on the estab- Rhizobacteria are free-living bacteria which can colonize the lishment of Rhamnus lycioides L. seedlings in both locations, rhizosphere and improve root system establishment (Antoun as well as their effect on soil chemical and microbiological and Kloepper 2001), improving plant health and nutrition properties. The information gained here will enable us to es- (Adesemoye and Kloepper 2009; Benabdellah et al. 2011; tablish effective criteria for the selection of strains for use in Mengualetal.2014;Puenteetal.2004; Schoebitz et al. the revegetation of semiarid environments. 2014;Pilietal.2015). Furthermore, it has been shown that PGPR are able to synthesize some vitamins participating in physiological processes within plant-PGPR interactions Materials and methods (Palacios et al. 2014). Actinobacteria are one of the major components of soil microbial populations, comprising 10– Study areas 50 % of the soil microfloral community over a broad range of soil conditions (Hamdali et al. 2008a). They are able to The field assay was carried out in two different semiarid mineralize N and C, decompose organic material (Li et al. Mediterranean areas: Vicente Blanes Ecological Park in 2010), fix atmospheric N (Valdés et al. 2005), produce Rellano (coordinates 38°12′50.8″ N, 1°13′30.9″ W) and phytohormone-like compounds, and behave like biocontrol Calblanque Nature Reserve (coordinates 37°36′22.7″ N, agents (Tarkka et al. 2008)—properties that benefit plant 0°45′20.3″ W), both in the Province of Murcia, Spain. The growth (Hamdali et al. 2008b). Due to their multiple traits, soil is classified as a Typic Torriorthent (SSS 2010), very little the use of actinobacteria to favor the establishment of plant developed with low organic matter content that facilitates the species in semiarid environments is interesting. degradation of soil structure. This area supports vegetation Actinobacteria have displayed their potential as plant growth dominated by Piptatherum miliaceum (L.) Cosson and some promoting rhizobacteria (PGPR) under laboratory and green- shrubs of Thymus vulgaris L., Pistacia lentiscus L., Rhamnus house conditions (De Vasconcellos and Cardoso 2009; lycioides L., Cistus clusii Dunal, and Rosmarinus officinalis Franco-Correa et al. 2010; Shishido and Chanway 1998), L. Calblanque Nature Reserve had a mean annual temperature but knowledge of their effectiveness under field conditions of 18.7 °C and no frost period. The soil is a Lithic Torriorthent is scarce—being limited to assays in agricultural ecosystems (SSS 2010). The vegetation in this study site is composed by (Jog et al. 2014). Meanwhile, no studies on the employment of several shrubs species such as Tetraclinis articulata (Vahl) actinobacteria to promote the establishment of plant species in Mast., Rhamnus lycioides L., Maytenus senegalensis (Lam.) revegetation programs have been conducted. Loes., Periploca angustifolia Labill., and Calicotome It has been proven that microorganisms that are native to a intermedia C. Presl in Abh., and some tree species like particular soil—such as arbuscular mycorrhizal fungi (Bashan Pinus halepensis Mill. and Chamaerops humilis L. During et al. 2012;Caravacaetal.2003;Ouahmaneetal.2007, 2006) the experimental period, the annual mean precipitation was or Bacillus strains (Armada et al. 2014; Ortiz et al. 2014)—are 265 mm, being the rainfalls mainly concentrated in often successful inoculants in revegetation tasks, presumably November 2012 and spring 2013. The annual mean tempera- as a result of their adaptation to specific edaphic and environ- ture was 18.7 °C, reaching the maximum temperature of mental conditions (Schreiner 2007). However, the efficacy of 26.7 °C in the summer months. Soil characteristics in both native strains of actinobacteria in comparison with allochtho- locations are reported in Table 1. nous strains, regarding enhancement of plant growth, has not been investigated. We hypothesized that variations among Plant material actinobacterial strains from different sites could lead to dis- tinct effects on plant growth and nutrient uptake. The aims of The plant used was Rhamnus lycioides L. (Rhamnaceae), a this study were (1) to ascertain if the positive effects of perennial shrub which can reach a height up to 3 m, naturally actinobacteria are maintained when the strains are inoculated occurring in the Western Mediterranean Basin, which can be in soils different from their isolation source, (2) to verify the found from sea level up to 1000 m (Gulías and Traveset 2012). relevance of the strain origin to the ability of actinobacteria to This is a representative autochthonous species from semiarid enhance plant growth under semiarid field conditions, and (3) areas in southeast Spain, well adapted to water stress condi- to unravel the mechanisms which account for the differences tions and high temperatures, used frequently in the revegeta- in the ability of native actinobacterial