Serratia strains isolated from the rhizosphere of raulí ( Nothofagus alpina ) in volcanic soils harbour PGPR mechanisms and promote raulí plantlet growth

Abstract

Raulí is one of the most emblematic tree species of the Chilean temperate forests. Due to the high quality wood, this tree has been used for furniture and handicrafts manufacturing, which has positioned raulí as one of the most important commercial timber species in Chile. Currently, the international market demands sustainable production system for forest production, more specifically in plantlets production. In this regard, plant growthpromoting rhizobacteria (PGPR) inoculants may enhance the growth and survival of plantlets in nurseries, which means an increase in the effectiveness of replanting operations. Therefore, the aim of the present study was to isolate, characterize and screen rhizosphere-associated bacteria with PGPR potential, isolated from raulí that growth in volcanic soils in southern Chile. A total of 1,261 bacterial strains were isolated from different volcanic soils. Out of 1,261 isolates, 100 were selected based on their high levels of indole acetic acid (IAA) production. These isolates were then subjected to screening for 1-aminocyclopropane-1-carboxylic acid deaminase activity, and their ability to fix nitrogen was determined. From the 100 selected isolates, 7 were chosen for producing the highest amount of IAA to continue with genetic characterization based on their 16S rRNA gene sequences. These 7 isolates were characterized as members of the Serratia genus and were used to develop multi-strain inoculant mixtures. Later, a nursery study followed to determine the effect of inoculation with the Serratia strains on the growth of RA88 raulí clone plantlets. The nursery experiment demonstrated that Serratia strains have the potential to increase the root collar diameter, height, relative chlorophyll content, biomass and nitrogen content of raulí plantlets. The study concluded, that Serratia strains have the potential to be used as biofertilizers to increase plant growth in nursery conditions.

Pseudomonas fluorescens and Azospirillum brasilense Increase Yield and Fruit Quality of Tomato Under Field Conditions

“…The different letters indicate significant differences using Fisher's LSD test at P < 0.05 a Expressed as citric acid equivalent be different than the effect produced by each bacterium alone. However, other authors reported positive effects by using different consortiums in maize (Couillerot et al 2013), cucumber (Wang et al 2012), forage plants Mavuno grass (Sá et al 2019), and forest species Nothofagus alpina (Martínez et al 2018). These contradictory results with the use of combinations may be related to the correct concentration of each inoculum.…”

Improved Growth and Nutrition of Sorghum (Sorghum bicolor) Plants in a Low-Fertility Calcareous Soil Treated with Plant Growth–Promoting Rhizobacteria and Fe-EDTA

“…Plant growth-promoting rhizobacteria as biofertilizer can improve plant growth by increasing the soil nutrient bioavailability and uptake by plant from a low-available soil nutrient pool (Gouda et al 2018). A wide range of PGPR can increase plant growth and yield, by such processes as nitrogen fixation; increasing the availability of Fe through production of siderophores; the production of phytohormones such as auxins, cytokinins, and gibberellin; declination of ethylene tension (Zaidi et al 2006;Martínez et al 2018); and production of organic acids, chelating agents, and mineral acids (like H 2 SO 4 and HNO 3 ) that can dissolve insoluble P to increase the availability of P and Zn in the soil (Dinesh et al 2018). Plant growth-promoting rhizobacteria can also promote plant growth by various mechanisms such as increasing the supply of nutrients, increasing root biomass or root surface area, and increasing nutrient uptake capacity of plants (Paungfoo-Lonhienne et al 2019).…”

Selecting the most effective plant growth-promoting bacteria from oil palm (Elaeis guineensis Jacq) roots

“…and, EN9 was identified as Pantoea sp. Bacterial isolates which were identified as Bacillus, Serratia, and Pantoea were among common and widely reported genera belong to plant growth-promoting rhizobacteria group (Martínez et al, 2018;Aziz, 2015;Susilowati et al, 2015). E. coli strain EX2 which much related to clinical strain or human pathogen was rarely found as plant growth-promoting rhizobacterium species especially when exhibits multiple beneficial traits.…”