Piper betle L., a vital and widely cultivated asexually propagated cash crop, belongs to the Piperaceae family. It is a shade-loving perennial creeper with broad, heart-shaped leaves that vary in color from pale green to bright green or yellowish-green (Guha and Nandi, 2019). These large leaves are aromatic, offering a range of flavors from sweet to spicy (Ravindran et al., 2004). Endophytes, including bacteria and fungi, are microorganisms that form endosymbiotic relationships with various plants and are found throughout different plant parts, such as roots, stems, leaves, bark, floral organs, and seeds (Hallmann et al., 1997; Compant et al., 2011; Dudeja et al., 2012). These endophytes have been extensively studied for their ability to promote plant growth, and their presence is well-documented in various plant species. Plant growth-promoting bacteria (PGPB) play a crucial role in aiding nutrient acquisition through mechanisms like phosphate solubilization, nitrogen fixation, ammonia production, and siderophore production. Additionally, plant-associated microorganisms improve nutrient uptake by making minerals and other macro/micronutrients more accessible from the soil (Caldwell et al., 2000; Barrow, 2003). As a result, there is a great deal of promise for enhancing plant development in the isolation and characterisation of endophytic bacteria with a variety of characteristics from unexplored host plants. (Patten and Glick, 2002; Sergeeva et al., 2007). One effective approach for promoting plant growth and modifying plant structure involves the use of endophytic bacteria that influence phytohormones. These bacteria have demonstrated significant potential in agricultural applications due to their distinctive properties (Hallmann et al., 1997; Sturz et al., 2000).
Continuous agricultural practices, such as fertilization, have the potential to cause significant environmental harm on a global scale. These practices can lead to unintended negative consequences, including the accumulation of chemical residues and the disruption of ecosystems (Shenoy et al., 2001; Adesemoye et al., 2009; Hazell et al., 2007). In response to these environmental concerns, biofertilizers have emerged as a sustainable alternative to conventional farming methods. These biofertilizers contain beneficial microbes that form symbiotic relationships with plants, thereby enhancing plant health and growth. This results in improved agricultural outcomes, including increased root and shoot length, greater fresh and dry weight of shoots and roots, higher yield production, and enhanced soil quality and nutrient cycling (Soliman et al., 2019; Elkelish et al., 2020). The objective of this study was to evaluate the effectiveness of four plant growth-promoting bacteria treatments on betel leaf cultivation by measuring plant growth and yield.