Effect of Pseudomonas Fluorescens in the Germination and Growth of Prosopis Laevigata under Greenhouse Conditions

The mesquite [Prosopis laevigata (Humb. Et Bonpl ex Wild.) M.C. Johnst], a multi-purpose tree (Rodríguez-Sauceda et al., 2014), is used as a source of energy, a natural barrier, feed for livestock, getting gums and for medicinal (Prieto-Ruíz et al., 2013). In addition, it has important ecological functions because it allows erosion control, atmospheric nitrogen fixation and improves soil quality (Stanton et al., 2001; Buendía-González et al., 2012; Palacios-Romero et al., 2017). All these characteristics make it a species of interest to exploit and cultivate in arid and semi-arid areas, since according to Villanueva-Díaz et al., (2004), cited by Palacios-Romero et al., (2017), this woody species has a wide distribution in arid and semi-arid areas of northern and central Mexico. However, cultivating species in arid and semi-arid environments requires generating new technologies (Prieto-Ruíz et al., 2013). Mia et al., (2012) stated that the development of any plant species depends on various factors such as the vigor of the seed for effective germination, and the rapid establishment of the plant (Bécquer et al., 2013). In this sense, with the purpose of new production options, the use of plant growth-promoting microorganisms (PGPM) as biofertilizers (Afzal and Bano, 2008) they considered a solution and an alternative to promote plant growth and nutrition (Vessey, 2003; Jaiswal et al., 2016). In fact, the use of such fertilization sources has attracted the attention of researchers because of their success in crop development and their low ecological footprint (Egamberdieva, 2008; Karakurt et al., 2011; Radhapriya et al., 2015) in relation to chemical fertilizers (Vessey, 2003; Dadrasan et al., 2015).

Among the plant growth-promoting microorganisms, it gives great emphasis to the study of the group of fluorescent Pseudomonas bacteria, either to increase agricultural production or for its various related benefits by the association of bacteria on plant roots (Carrillo-Castañeda et al., 2000; 2011). For leguminous species, many authors report that P. fluorescens, selected as plant growth-promoting Rhizobacteria, are a source of nutrients, where plant root colonization (Siddiqui et al., 2001; Egamberdieva et al., 2013) stimulates growth (Vessey, 2003) and director indirect production (Shaukat et al., 2006, Afzal and Bano, 2008; Iqbal et al., 2012).

They have shown the plant growth-promoting capacity of bacteria of the genus Pseudomonas through the "biofertilizing effect" and also for its ability to antagonize multiple pathogenic microorganisms (Pal et al., 2001). In addition, they have considered that natural reforestation in eroded areas of the desert is very difficult because, in these degraded soils, the surface layer of the soil has lost the microorganisms that promote the development of plants. That is why, by artificially reforesting these areas, we recommend inoculating the seeds of the plants with microorganisms to return to the soil part of their fertility and potential for the development of plants. Drezner, (2006) mentioned that only good irrigation with water will not restore fertility and soil microbial communities.

That is why we considered in this work pertinent to determine the specificity and positive or negative effects of bacterial cells associated with mesquite seeds and roots as an ecological strategy to promote the growth of plants within an utilization perspective of natural and biological fertilizers. Thus, in this study, we tested the significant importance of an inoculation with cells of the bacterial strains A7 and Sv of P. fluorescens in two physiological stages, germination, and the development of mesquite. In addition, we suggested two hypotheses. The first is that the use of bacterial strains favors the germination process of mesquite. Meanwhile, the second one is that the use of these plant growth-promoting microorganisms favors the initial development stage of this tree species.