The combined effects of Pseudomonas fluorescens CECT 844 and the black truffle co-inoculation on Pinus nigra seedlings

Abstract

© iForest -Biogeosciences and Forestry IntroductionWater and nutrient availability are the main constraints on plant productivity in semi-arid Mediterranean ecosystems. The preservation of mycoflora diversity depends on the status of plant roots (Marulanda et al. 2006). Forest species in these areas often develop specific strategies to improve their water usage in response to drought (Martínez-Ferri et al. 2000).Several studies have been conducted to improve the quality of seedlings produced in nurseries (Caravaca et al. 2005). Several authors reported that soil amendment with ectomycorrhizal fungi and plant-growth-promoting rhizobacteria (PGPR) increased plant survival and seedling quality, especially in soils with low microbial activity (Chanway 1997, Probanza et al. 2001.Pseudomonas fluorescens generally shows several characteristics of an effective PGPR. It is easily cultivated in vitro, and it colonizes a wide range of ecological niches, including plant rhizospheres (Bolton et al. 1993). Additionally, P. fluorescens genomes are highly diverse, which most likely increases the P. fluorescens survival (Silby et al. 2009). The ecological flexibility of such bacteria allows them to exploit a wide variety of nutrients to adapt to environmental changes for survival. P. fluorescens also improves plant growth by producing phytohormones such as auxins (e.g., IAA -Karabaghli et al. 1998). It also has a high capacity for phosphorus solubilization and can produce siderophores (Matthijs et al. 2007). Despite the very well-known positive effects of P. fluorescens on plant survival, only a few studies have been conducted to study its influence on the growth of forest species (Rincón et al. 2008, Ouahmane et al. 2009). We recently demonstrated that the inoculation of Aleppo pine (Pinus halepensis Mill.) with P. fluorescens CECT 844 improved the vegetative growth and N absorption of the P. halepensis seedlings (Dominguez et al. 2012).The use of environmental-friendly natural microbial inocula, such as PGPR or mycorrhizal fungi, is presented in this study as a potential alternative fertilizers. These microorganisms are also beneficial for the maintenance of pre-existing soil microflora, thus contributing to the conservation of soil biodiversity. The amended soil in the nursey increases the vegetative vigor and morphophysiological quality of forest species growth for reforestation purposes (Chanway 1997).Information regarding the productivity of ectomycorrhizal fungi, their ecological functions and their contributions to the productivity and recovery of altered agroecosystems is increasingly valuable in agroforestry. In Spain, the black truffle (Tuber melanosporum Vitt.) is of substantial economic and social value in rural areas of the Mediterranean (Reyna 2007), although studies on the contributions of T. melanosporum to the growth and physiology of forest plants are scarce (Domínguez-Nuñez 2002). Moreover, the ecological value of such symbiosis in the recovery of Mediterranean ecosystems has not been well characterized.The...

Use of Inoculator Bacteria to Promote Tuber melanosporum Root Colonization and Growth on Quercus faginea Saplings

“…Furthermore, even though bacterial growth media inoculations were a source of nutrients and could positively affect seedling roots as a fertilizer, promoting plant growth and/or mycorrhization rates, we did not observe any differences in the mycorrhization rates or root seedling traits when bacterial growth media were added to the seedling substrate compared with that of control seedlings. To the best of our knowledge, none of the T. melanosporum and bacteria co-inoculation trials performed to date have assessed the possible effects of bacterial growth media on either fungal colonization or root development [24,25,31].…”

“…In parallel, because the bacterial community is very dynamic in soil [22,23], bacterial inoculations were performed one month and nine months after T. melanosporum inoculation to determine whether the application time influenced the outcomes. Some previous studies have developed methods involving the simultaneous co-inoculation of bacteria and fungi [24,31]; however, here, we avoided using a simultaneous inoculation method to assess whether co-inoculation really promotes mycorrhizal formation after a symbiotic association has already formed [32].…”

Cepas de bacterias aisladas de esporomas de hongos ectomicorrízicos promueven el crecimiento vegetal

“…Las bacterias auxiliadoras de la micorrización y promotoras del crecimiento tienen un gran potencial de uso en viveros forestales como varios estudios lo demuestran (Dominguez-Nuñez et al, 2015), y posiblemente su efecto benéfico no se restringa solo a sus hospedantes arbóreos sino que se extienda a otras especies como cultivos agrícolas. En este trabajo se estudió el potencial de un grupo de cepas de rizobacterias aisladas de esporomas del hongo ectomicorrízico Lactarius salmonicolor R. Heim & Leclairde para promover crecimiento, usando como planta indicadora a chile Serrano (Capsicum annuum L.), una hortaliza ampliamente cultivada en México y otros países del mundo.…”

The alleviation of reforestation challenges by beneficial soil microorganisms

“…Beneficial microorganisms are well known, due to their ability to colonize and elicit stimulant effect on plant growth and health. Also, they represent an alternative to conventional fertilizers and contribute to the conservation of soil biodiversity (Dominguez-Nuñez et al 2015). Soil microorganisms are getting more and more popular as bioremediation agents as well (Kavamura et al 2008Jovičić Petrović et al 2014;Atanasković et al 2015).…”

“…Literature data emphasize that soil amendment with beneficial microorganisms increase plant survival, seedling quality, and represents an alternative to mineral fertilizers (Chanway 1997;Probanza et al 2001;Dominguez-Nuñez et al 2015). The main stock of beneficial microorganisms is rhizosphere, the soil layer closest to the roots.…”