Native plant growth promoting rhizobacteria improve the growth of pepper seedlings and modify the phenolic compounds profile

In the establishment of a highly productive pepper crop, obtaining quality seedlings is a decisive step. An alternative to boost rapid plant growth has been the use of plant growth promoting rhizobacteria (PGPR). The study of PGPR and its effect on different plant species has made it possible to establish, among other physiological parameters, a direct correlation between total phenolic compounds and a positive systemic response induced in plants, which could act as growth regulators. The evaluation of the phenolic compound profile and its change in relation to PGPR-pepper seedlings interaction, using liquid chromatography, has scarcely been reported. The aim of the present study was to evaluate changes in the morphology, nitrogen (N) accumulation and the phenolic compounds profile produced by the inoculation of four native PGPR strains: Pseudomonas 42P4, Cellulosimicrobium 60I, Enterobacter 64S1, and Ochrobactrum 53F during the growth of Calahorra pepper seedlings (cv. Calafyuco INTA). Our results showed that all the PGPR tested can promote growth in pepper seedlings. However, Pseudomonas 42P4 and Cellulosimicrobium 60I1 were more effective in increasing N uptake, and improving the morphological, biochemical, and physiological parameters in pepper seedlings. Flavonoids, such as naringenin, naringin, and catechin, could favor growth in plants inoculated with Pseudomonas 42P4, whereas only catechin in Cellulosimicrobium 60I1. The combined effect of gallic acid, hydroxytyrosol, tyrosol, phloridzin, and the exacerbated production of (-)-epigallocatechin gallate may contribute synergistically to limiting the growth of Control seedlings. Finally, PGPR applied in this study could be used as biofertilizers, thereby reducing the use of nitrogen fertilizers, cutting down on production time and cost, and improving the quality of seedlings for horticulturists and nurseries.

Automated summary

The study shows that plant growth promoting rhizobacteria (PGPR) can promote the growth of pepper seedlings, with pseudomonas and cellulosimicrobium species being more effective. Different phenolic compounds play a positive role in enhancing plant growth. The findings are significant for reducing nitrogen fertilizer use, shortening production time, and improving the quality of seedlings.