## 1 Introduction  
Several species belonging to the \(Brassicaceae\) Burnett family are economically important plants, i.e., oil and fodder plants in agriculture, vegetables in horticulture including herbal species, and plants used in floriculture. The model plant \(A\). _thaliana_ also belongs to this plant family. The genus \(Brassica\) contains 37 species; the most extensively cultivated are \(B\). \(rapa\) L., \(B\). \(juncea\) L. [PERSON] (mustard plant), \(B\). \(napus\) L. (oilseed rape, rape, rapeseed, canola), and \(B\). \(earinata\) A. Braun (Abyssian cabbage) [1]. Rapeseed is a crop plant cultivated in temperate and subtropical regions, mainly for oil production purposes, as seeds of this plant are rich in fat (40-49%). The rapeseed oil is used in both the food industry, as it is one of the healthiest oils, and the energy industry, to produce biofuel. Rape oil by-products are utilised for the production of fodder due to their high protein content [2]. Rapeseed is cultivated all over the world, depending on climatic conditions and latitudes; three types, i.e., the winter, semi-winter, and spring types, are cultivated with varying intensity [3]. \(B\). \(napus\) is an allopolyploid plant (\(A_{\rm r}A_{\rm r}C_{\rm o}C_{\rm o}\)); its genome is a result of \(B\). \(oleracea\) (Mediterranean cabbage, \(C_{\rm o}C_{\rm o}\)) and \(B\). \(rapa\) (\(A_{\rm r}A_{\rm r}\)) genome hybridization, followed by duplication. The genome of \(B\). \(napus\) has already been sequenced [4]. The crop yield depends strictly on the ability of plants to adapt to adverse and changeable environmental conditions, which is especially important during seed germination,and during the first stages of plant growth and development. Soil salinity is one of the crucial environmental stresses that have severely decreased crop productivity all over the world. It negatively affects plant physiology and metabolism, including photosynthesis, lipid metabolism, protein synthesis, and nitrogen fixation [5]. The abundance of Na\({}^{+}\) and Cl\({}^{-}\) inhibits absorption of other macronutrients causing nutritional imbalance. Moreover, salinity leads to water stress, increased reactive oxygen species production, and oxidative stress [6; 7]. Plant growth-promoting rhizobacteria (PGPR) exert several beneficial effects on host plants by promoting plant growth and development, including in stress conditions, via varied mechanisms, such as the production of phytohormones, secondary metabolites, and antibiotics [8; 9; 10]. Plant growth promoting bacteria, especially halotolerant bacteria, could be a crucial factor for improving plant tolerance to salt stress in an environmentally friendly way [8; 9]. PGPR isolated from the rice rhizosphere improved the growth of rice plants exposed to salt stress by lowering the level of ethylene [10]. _Serratia liquefaciens_ KM4 increased the growth and biomass of maize grown in salt-stress conditions, and the increased expression of plant stress-related genes has been observed [6]. The inoculation of lettuce with _Pseudomonas mendocina_ has a greater effect on plant growth in salt stress conditions than inoculation with arbuscular mycorrhizal fungi. In the presence of analysed PGPR the induction of a plant antioxidant system was observed, even in severe salinity conditions [11]. The inoculation of tomato with PGPR, especially _Arthobacter_ sp. and _Pseudomonas_ sp., under salinity stress outperformed chemical fertilization [12]. Organisms living in a fluctuating environment have evolved a range of mechanisms to respond to various stress conditions. Among several other mechanisms in bacteria, one of the most important is the stringent response. It was first described in _Escherichia coli_ in response to the absence of amino acids [13]. The response is based on the synthesis of the atypical signalling nucleotides, guanosine tetraphosphates (ppGpp) and guanosine pentaphosphates (pppGpp), called alarmones.