Plant growth promoting Rhizobacteria for sustainable tomato production

Numerous phosphate solubilizing bacteria (PSB) are found in the rhizosphere, benefiting the host plant in different mechanisms and promoting sustainable agriculture. They improve soil fertility with minimum cost requirements using an eco-friendly approach, which is an essential attribute for small-scale farm production. Thus, isolation, characterization, and evaluation of symbiotic effectiveness are hierarchical procedures to develop bioinoculants. Using a dual (plate and liquid medium) screening technique and a greenhouse trial, four potential PSB strains (Mk-1-25, Mk-13-16, Mk-20-7, and Mk-20-20) were selected from tomato rhizosphere soil. All isolates exhibited the following traits: produced colony clear-zone, lowered liquid medium pH, gram-positive, produced urease and IAA, dissolved substantial P from various substrates, symbiotically effective, and improved tomato growth and yield. Taxonomically, they belong to Bacillus and Priestia species (i.e., Mk-1-25 Bacillus halotolerance, Mk-13-16 Bacillus amyloliquefaciens, Mk-20-7 Bacillus megaterium, and Mk-20-20 Priestia megaterium). Among the current strains, Bacillus halotolerance recorded higher SI (3.11), was able to grow in extreme conditions (10% salt, up to 45 degrees C), produced HCN and siderophore, and improved tomatoes' shoot length and weight, in contrast, Mk-20-20 produced HCN, siderophore, was able to fix nitrogen, improved tomato germination, shoot dry weight, and fruit weight. Various P-supplements (Ca-3(PO4)(2), bonemeal, FePO4, AlPO4, compost, and DAP fertilizer) were added to induce tomato-strain symbiotic interaction; hence, compost substantially promoted the interaction and resulted in higher symbiotic effectiveness. Ca-3(PO4)(2) was a good media composite preferred by most PSB strains; consequently, a higher concentration (219 mu g/ml) of dissolved P was recorded from the liquid medium after 10 days of incubation than other substrates. Based on the data obtained from laboratory and greenhouse trials, the current strains were found to be potential candidate. Future work should confirm their efficacy at the field level using model host crops at different sites to recommend them as farm inputs and biofertilizer. (c) 2024 SAAB. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.