Isolation and <i>in vitro</i> screening of plant growth promoting bacteria from rhizosphere and root tissues of potato tuber (<i>Solanum</i> <i>tuberosum</i> L.)

The accumulation of chemical fertilizers that harm the environment is one of the major Indonesian agricultural problems. However, it still has less effect on potato production and yield. The discovery and use of bacteria that have the potential as plant growth-promoting agents (PGPR) is a breakthrough that can help to increase growth to increase production, especially in potato plants. In this study, several bacteria successfully isolated from the rhizosphere and root tissue of potato plants (Solanum tuberosum L.) were isolated from potato farms in Plaosan Village. Several in vitro screenings were carried out to assess the functional activity of plant growth promoters, including the IAA (indole-3-acetic acid) production test, siderophore production test, ACC (1-aminocyclopropane-1-carboxylate) deaminase production test and phosphate dissolution test. Based on the screening results, five isolates were considered as the best inoculants, there are R1.3, R2.2, JR2.1, E1.2 and E1.2.1. All R1.3, R2.2, E1.2 and E1.2.1 isolates were known to have the ability to produce phytohormones IAA, ACC deaminase, and siderophores. In contrast, JR2.1 isolate was not known to have the ability to fix nitrogen and produce IAA, ACC deaminase and siderophores. These isolates could be used as potential biofertilizer inoculants and provide a step towards sustainable agriculture.