Oak (Quercus robur) Associated Endophytic Paenibacillus sp. Promotes Poplar (Populus spp.) Root Growth In Vitro

Abstract

Soil fertilization is necessary for high-demand crop production in agriculture and forestry. Our current dependence on chemical fertilizers has significant harmful side effects. Biofertilization using microorganisms is a sustainable way to limit the need for chemical fertilizers in various enterprises. Most plant endophytic bacteria have thus far been unstudied for their plant growth promoting potential and hence present a novel niche for new biofertilizer strains. We isolated English oak (Quercus robur) endophytic bacteria and tested them for plant growth promoting traits (PGPTs) such as nitrogen fixation, phosphate mineralization/solubilization, siderophore and indole-3-acetic acid (IAA) production. We also investigated the effect the selected isolate had on poplar (Populus spp.) microshoot vegetative growth parameters in vitro. In total 48 bacterial strains were isolated, attributed to Bacillus, Delftia, Paenibacillus, Pantoea and Pseudomonas genera. All the isolates displayed at least three PGPTs, with 39.6% of the isolates displaying all five (all were Pseudomonas spp.) and 18.75% displaying four. Based on relative abundance, Paenibacillus sp. isolate was selected for the poplar microshoot inoculation study. The isolate had a significant positive effect on poplar microshoot root growth and development. Two tested poplar genotypes both had increased lateral root number and density, fresh and dry root biomass. Furthermore, one genotype had increased length and number of adventitious roots as well as a decrease in fresh aboveground biomass. The root enhancement was attributed to IAA production. We propose this isolate for further studies as a potential biofertilizer.

Impact of Plant-Associated Bacteria on the In Vitro Growth and Pathogenic Resistance against Phellinus tremulae of Different Aspen (Populus) Genotypes

“…Additionally, hybrid aspens responded with decreased viability not only to the fungus, but also to the bacterial treatments. This demonstrates that bacteria may affect different genotypes differently, as is noted in other studies [9,54,55], as well as becoming opportunistic pathogens [84].…”

“…Different bacteria have been successfully studied in attempts to control various plant pathogens and promote plant growth [ 46 , 47 , 48 , 49 , 50 , 51 ]. Both Pseudomonas and Paenibacillus species have been shown to have positive effects on plant growth in previous studies; this is sometimes linked with nitrogen fixation or phytohormone production [ 9 , 48 , 52 ], etc. In previous studies, Paenibacillus sp.…”

“…In previous studies, Paenibacillus sp. were shown to have a positive effect not only on Populus root-system growth in vitro [ 9 , 53 ], but also on other trees [ 54 , 55 , 56 , 57 ]. Additionally, both bacterial genera have attracted considerable interest because of their ability to degrade chitin, a key compound found in the walls of fungal cells [ 46 , 58 ].…”

“…Endophytic bacteria can promote resistance to stress and pathogens, at the same time stimulating nutritional processes in their hosts, hence affecting overall growth [ 5 , 6 , 7 , 8 ]. Plant microorganisms can benefit their hosts through a variety of mechanisms, including biological nitrogen fixation and increased bioavailability of phosphorus (P), iron (Fe) and other mineral nutrients, as well as production of plant hormones and various antimicrobial biocontrol compounds [ 7 , 9 , 10 , 11 ]. Plant growth promoting bacteria are being more widely used in agriculture, as an eco-friendly alternative to chemical fertilizers and pesticides [ 7 , 12 ]; however, the potential application of such beneficial bacteria in forestry has not yet been sufficiently explored [ 13 ].…”

Differentiation of Closely Related Oak-Associated Gram-Negative Bacteria by Label-Free Surface Enhanced Raman Spectroscopy (SERS)

“…Pseudomonas spp.) [ 35 , 36 , 37 , 38 , 39 , 40 ]. In the field of plant-associated bacteriology, using SERS for the differentiation and identification of bacteria would likely prove to be highly beneficial and efficient [ 16 , 22 , 29 , 30 , 41 ], as different species and even different strains of the same species may have vastly different effects on plant growth [ 42 ].…”