Enhancing Peach Tree Fertilization: Investigating Methylobacterium symbioticum SB23 as Game-Changing Agent

This study aims to evaluate the potential of a nitrogen-fixing endophyte, Methylobacterium symbioticum SB23, as a sustainable biofertilizer in peach (Prunus persica) cultivation. We compared three treatments: a control with soil application of ammonium sulfate (250 kg ha−1) and two endophyte foliar applications at different doses: a single high-dose application (M.SYM500 at 500 kg ha−1) and a split half-dose application (M.SYM250 at 250 kg ha−1 applied twice). The first application was made at the fruit stage’s appearance, and the second when the fruits were fully developed. Key assessments included chlorophyll content and shoot growth, which were evaluated at 52 and 100 days after application (DAA), with continued growth benefits observed through 193 DAA. Evaluations were conducted of fruit characteristics, amino acid profiles, and plant tissues of leaves for nitrogen and phosphorus at 107 DAA (harvest). The M.SYM500 treatment notably enhanced fruit weight and increased specific amino acids, such as glutamic acid, methionine, and phenylalanine, contributing to improved fruit quality and resistance properties. No significant differences in °Brix (total soluble solid) levels were observed among treatments, indicating that photosynthetic gains were likely directed towards biomass and structural growth rather than sugar accumulation. This study demonstrates that nitrogen-fixing endophytes can be effective in reducing reliance on synthetic fertilizers while sustaining or improving peach growth and fruit quality.