Spinach (Spinacia oleracea) is one of the important leafy vegetable belonging to family Amaranthaceae (Hanif et al., 2006; Kisan et al., 2015) with its subfamily of Chenopodioideae. The plant of spinach grows up to a height of 30cm and the leaves of spinach are simple, alternate, ovate, triangular, and can be smooth or curly (Tewani et al., 2016). The leaves of spinach varying in size from 1–12 inches in length and 1-15cm in width (Sree et al., 2013). Spinach has different varieties which are resistant to different diseases. These varieties are categorized into 3 types; spinach savoy that has dark greeny color, wrinkly and crimped leaves, smoothy leaf spinach that has wide, flat or plane leaves, semi-savoy spinach which is a hybrid of savoy and smooth leaf spinach and has slightly wrinkled leaves (Shah et al., 2015).
Pakistan occupies 10th position world wise for production of spinach. (Shah et al., 2015). In Pakistan, the total yield of spinach is 12588 kg per hectare (Faostat, 2012; Shaheen et al., 2017). In Pakistan, spinach is being used as a favorite food due to its high nutritional status and has great economic importance. As it contains high quantity of essential minerals and nutrients including vitamins, flavonoids, and folic acid (Liu et al., 2015). In spinach high amount of vitamin K and calcium is also present which are used to strengthen the bones. Manganese present in spinach is essential for regulation of blood sugar, calcium assimilation, and metabolism. Cooked spinach has a high amount of minerals, for example, iron, magnesium, copper, calcium, and potassium which get easily absorbed through the body (Patricia et al., 2014; Miano, 2015). The green leaves of spinach have pharmacological and medicinal properties that are excellent for the health of humans. It improves the nutritional status in humans and decreases the risk of many diseases in humans such as diabetes, hepatotoxicity, and cancer (Fornaciari et al., 2015). The use of spinach also decreases the threat of cardiovascular disease, strokes, hypertension (Ngo et al., 2005; Rahati et al., 2016) and cardiovascular diseases. It is also helpful in the cure for tooth and respiratory disorder, gastrointestinal disorders, asthma (Aziz et al., 2016; Khan et al., 2018), acidosis, anemia, constipation (Ugulu, 2012), pregnancy and urinary disorders (Shah et al., 2015). One of the fact concerning with the production of vegetables is that organically grown vegetables donot satisfy the appropriate demand of food. However, employment of chemical fertilizers for the improved production of dietary vegetables has been a common practice on worldwide scale (Stewart et al., 2005). The frequent application of synthetic fertilizers not only increases the production rate but also influence the health and nutritional status of essentially required crops (Singh et al., 2001; Raman et al., 2022). The current scenario demands for the alternate source of toxic chemical fertilizers, for safer production of crops. However, large number of soil borne microflora of the crops can serve the suitable purpose offering satisfactory nutritional requirements (Singh et al., 2022).
Multifarious microbes present around the plant’s root are called rhizobacteria and those bacteria existing inside the plant’s cells are called as endophytic bacteria. These endophytic bacteria act as plant growth promoters (PGPB) imparting their role in growth promotion by adopting both direct and indirect mechanisms (Parray et al., 2016; Kalam et al., 2017). While implementing the direct means of growth improvement, these endophytes may produce multiple hormones such as auxin (Ahemad & Kibret, 2014; Qi et al., 2018), cytokinin, gibberellins, ACC deaminase, and also contribute in nitrogen fixation, phosphorus solubilization, and siderophore production (Ji et al., 2014; Tahir et al., 2017; Qi et al., 2018). However, the indirect ways of bacterial flora constitute the prevention from plant pathogenic micoorganisms (Podile & Kishore, 2006; Zhou et al., 2016; Kalam et al., 2017) by means of secretion of cell wall degradating enzymes, antimicrobial components as well as through HCN production (Balogh et al., 2010; Frampton et al., 2012; Olanrewaju et al., 2017).
Plant growth promoting rhizobia (PGPR) comprise of such bacterial community which multiply faster around the plant roots enhancing the growth of the host plant and raising the crop yield, minimizing the chances of infection and diminishing the stress (abiotic and biotic) of plants. These growth promoters also promotes the detoxification of heavy metals in plants vicinity by production of effective volatile organic compounds into the interconnected environment (VOCs) (García-Fraile et al., 2015; Gouda et al., 2018). Acinetobacter, Algaligenes, Arthrobacter, Azospirillium, Azotobacter, Bacillus, Beijerinckia, Burkholderia, Enterobacter, Erwinia, Flavobacterium, Rhizobium, and Serratia genera are the plant growth-promoting rhizobacterial strains (Bashan & De-Bashan, 2005; Han & Lee, 2005; Erturk et al., 2011). The act of plant growth promotion may define the roles of these microbes as bio-stimulants, bio-fertilizers, and bio-protectants. The function of biofertilizers can be expanded to decrease the requirement of inorganic fertilizers and to minimize the unfavorable effect of the environment (Dobbelaere et al., 2003; Çakmakçı et al., 2007).
The purpose of the present research includes the isolation of rhizospheric bacteria from the rhizosphere of Spinach, preliminary identification and characterization of isolated bacteria and their evaluation as biofertilizers for development of two varieties of Spinacia oleracea (Desi palak and Lahori palak).