Highlights Bacillus licheniformis induced resistance against gray mold in pepper plants. Bacillus licheniformis and Bacillus pumilus inhibited the growth of Botrytis cinerea and Fusarium solani. Plant growth promoting mechanisms were confirmed by isolated Bacillus strains.

In a scenario of world population increase and climate change, an efficient use of water is key for agricultural production. Onion is one of the most profitable crops and can adapt to particular conditions of water stress. The objective of this research was to determine growing degree-days (GDD) and accumulated radiation under non-stress conditions, and yield of an F1 2000 hybrid of onion (Allium cepa L.) under water deficit and biofertilization in a semi-arid environment. An established nutrient requirement of 247 kg N, 240 kg P2O5 (105 kg P), 240 kg K2O (199 kg K) and two irrigation factors were applied: normal irrigation (NI) with a daily and water deficit (WD) with a three-day interval irrigation frequencies. The effect of biofertilization was evaluated through the inoculation of a microbial consortium in combination with four NPK fertilizer treatments. The crop accumulated 1334 °Cd and 1188 MJ m-2 d-1 at the time of harvest at 71 days after transplanting (DAT). The yield was 36 t ha-1, similar under both irrigation conditions; and the WD treatment resulted in a 35% water savings, a 47% and 65% increase in water use efficiency (WUE) and modulus of elasticity, respectively. The microbial consortium resulted in a 50% NPK savings under non-limiting water conditions and produced a similar yield compared to the 100% NPK non-inoculated control. The lower irrigation frequency together with the 100% NPK fertilization dose without the microbial consortium, and the use of the microorganisms and the 50% NPK treatment without water stress are recommended as agrosustainable practices for onion production.

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Las rizobacterias forman parte de la gran cantidad de microorganismos que actúan como agentes de biocontrol, produciendo metabolitos que inducen resistencia sistémica en las plantas que inhiben el crecimiento de patógenos. El objetivo de esta investigación fue evaluar la capacidad de diez rizobacterias de los géneros Rhizobium, Bradyrhizobium, Sinorhizobium, Ochrobactrum y Pseudomonas para producir ácido cianhídrico (HCN), sideróforos y ácido indol-acético (AIA), disolver fosfato, fijar nitrógeno e inhibir el crecimiento de fitopatógenos. Se realizaron todas las pruebas fisiológicas y bioquímicas correspondientes, así como la prueba de antagonismo in vitro contra los fitopatógenos Fusarium oxysporum, Colletotrichum gloeosporioides y Rhizoctonia solani.  Cinco cepas produjeron una mayor cantidad de AIA en relación a las otras en presencia de triptófano, la cepa ES1 (Ochrobactrum sp.) produjo HCN, el 50 % de las cepas evaluadas liberaron sideróforos, el 60 % disolvió fósforo, y todas resultaron positivas para la fijación de nitrógeno. Nueve cepas inhibieron el crecimiento de F. oxysporum entre 40 % y 65 %, la cepa Alf (Pseudomonas fluorescens) inhibió además el crecimiento de C. gloeosporioides en un 22 %, y ninguna inhibió el crecimiento de R. solani. Los rizobios evaluados y la cepa de Pseudomonas fluorescens podrían ejercer efectos beneficiosos sobre las plantas a través de mecanismos directos e indirectos, o una combinación de ambos, lo que las convierte en una opción sostenible para la producción de cultivos.

The practice of producing more vigorous seedlings represents a competitive advantage at the time of transplanting a crop, and the use of combined biofertilizers are a sustainable ecological alternative. The objective of this research was to select a microbial consortium for the production of F1 2000 hybrid onion seedbeds under shade-house conditions. Five rhizobacterial strains of the genera Rhizobium (ME01 strain), Bradyrhizobium (Leu2A and YE1 strains), Ochrobactrum (ES1 strain) and Pseudomonas (Alf strain), which have shown favorable effects on pepper and lettuce seedlings. These rhizobacteria were inoculated in a mixed manner (microbial consortium) in onion as follows: Alf+ES1, ME01+ES1, ES1+Leu2A, Alf+Leu2A, YE1+ES1, ME01+Alf, YE1+Alf, ME01+YE1, YE1+Leu2A, ME01+Leu2A, using a soil from San Juan de Lagunillas-Mérida, Venezuela under shade-house conditions for 60 days. The following variables were determined: number of leaves, pseudostem base diameter, aerial and root length, aerial and root fresh and dry weight. Additionally, a CO2 assimilation curve under different light levels was carried out on the seedlings of the selected consortium to observe their photosynthetic response. The consortium ME01 + Leu2A (Rhizobium tropici + Bradyrhizobium japonicum) increased all studied variables, especially the pseudostem base diameter, essential for onion cultivation, and yielded higher seedlings CO2 assimilation rates. The use of this microbial consortium is recommended as an option for agricultural production under seedbed conditions.