ABSTRACT The use of plant growth-promoting bacteria contributes to the sustainability of agriculture. Metabolic and morphometric variables, and their correlation with the initial growth of two tomato cultivars, were assessed in this study. This was done to evaluate the effect of seeds inoculated with Bacillus amyloliquefaciens subsp.plantarum FZB42in two doses: 20% of bacteriasuspension as inoculant solution (Ba20) and 80% of bacteria suspension as inoculant solution (Ba80), equating to 1.6 x 105 and 6.4 x 106 bacteria per seed, respectively. Bacterial inoculation increased the growth of roots at different rates, from 14.56% (total length in the 'Santa Clara I-530' cultivar) up to 197.13% (root volume of the 'Cherry 261' cultivar). Increments in the aerial part also varied from 12.06% (leaves area in 'Santa Clara 1-530，) up to 88.88% (dry matter in 'Cherry 261'). Increases in the root system with Ba20 were also correlated with an increase in the height and weight of the fresh matter of plant aerial parts. Metabolite concentration (sugars and soluble proteins) was closely related to leaf expansion according to the response of cultivars and doses. Ba20 (1.5 x 105 bacteria per seed) showed plant growth effects on two cultivars of tomato, which is promising for future studies.

RESUMEM El uso de bacterias promotoras del crecimiento de planta puede contribuir a la sostenibilidad de la agricultura. Metabólicos y variables morfométricas, y su correlación con el crecimiento inicial de los cultivares de tomate fue analizado en este estudio, con el objetivo de evaluar el efecto de la inoculación de semillas con Bacillus amyloliquefaciens subs. plantarum FZB42, usando dos dosis: 20% de suspensión de bacterias en la solución de inoculante (Ba20) y 80%c de suspensión de bacterias en la solución de inoculante (Ba80), la concentración estimada es 1,6 x 10 5 y 6,4 x 10 6 bacterias por semilla, respectivamente. La inoculación he proporcionado incremento de crecimiento en las raíces en proporciones diferentes, que van desde 14,56% (longitud total en la variedad 'Santa Clara I-530') a 197,13% (volumen en el cultivar 'Cherry 261'). Mientras que los incrementos de parte aérea variaron de 12,06% (área de las hojas de 'Santa Clara I-530') al 88,88% (materia seca de 'Cherry 261'). Los aumentos del sistema radicular en Ba20 se refleja en aumentos en la altura y peso de materia fresca de la parte aérea. Una concentración de metabolitos (azúcares y proteínas solubles) estaba estrechamente relacionada con la expansión de las hojas de acuerdo con la respuesta del cultivar y dosis. El Ba20 (1,6 x 10 5 ) mostró efecto significativo de la promoción del crecimiento vegetal en dos cultivares de tomate en crecimiento inicial, siendo prometedor para futuros trabajos.

ABSTRACT. The use of plant growth-promoting bacteria (PGPB), which aims to replace chemical fertilizers and biological control, is a goal for achieving agriculture sustainability. In this scenario, our goal was to identify and evaluate the potential of bacteria isolated from maize roots to promote plant growth and be used as inoculants. We evaluated 173 bacterial strains isolated from the maize (Zea mays L.) rhizosphere for the properties of their PGPB in vitro. Twelve strains were positive for siderophores, indole acetic acid (IAA) production, biological nitrogen fixation (BNF), and phosphate solubilization. Sequence analysis of 16S rRNA identified these strains as belonging to the genera Cellulosimicrobium, Stenotrophomonas, Enterobacter, and Bacillus. The elite strains were evaluated under greenhouse conditions upon the inoculation of two maize hybrids, ATL100 and KWX628. The ability of the isolates to promote plant growth was dependent on the maize genotype; Enterobacter sp. LGMB208 showed the best ability to promote growth of hybrid ATL100, while Enterobacter sp. strains LGMB125, LGMB225, and LGMB274 and Cellulosimicrobium sp. strain LGMB239 showed the best ability to promote growth of hybrid KWX628. The results highlight the potential of bacterial genera little explored as maize PGPB but indicate the need to investigate their interactions with different plant genotypes.