Endophytic PGPB Improves Plant Growth and Quality, and Modulates the Bacterial Community of an Intercropping System

Abstract

The intercropping of ryegrass and red clover constitutes a sustainable alternative to mitigate the adverse effects of intensive livestock production on grassland degradation by increasing forage yield and quality. The implementation of biofertilization technologies has been widely used to improve soil nutritional properties, and therefore has the potential to ensure the success of this multicrop system. To determine the impact of bioaugmentation on forage growth and quality, as well as the associate changes in the rhizosphere bacterial community, we evaluated the inoculation with two plant growth-promoting bacteria (PGPB) under reduced nitrogen usage. Overall, Herbaspirillum sp. AP21 had a larger effect than Azospirillum brasilense D7 on plant growth. Inoculation with Herbaspirillum sp. AP21 together with 50% of the required nitrogen rate increased shoot dry weight, crude protein, and shoot nitrogen content, and decreased the amount of neutral detergent fiber. PGPB inoculation changed the rhizosphere bacterial community structure, which associated with forage growth and quality. We conclude that PGPB inoculation has the potential to improve the growth of the ryegrass-red clover system, decreasing the requirements for nitrogen fertilization.

Differential Plant Growth Promotion Under Reduced Phosphate Rates in Two Genotypes of Maize by a Rhizobial Phosphate-Solubilizing Strain

“…This was a relevant condition of this study provided by the soil used, low P availability (12.28 mg kg −1 ), and reduced doses of P fertilizer applied. Abiotic stresses in plants (e.g., nutritional, saline, or drought stress) have been reported in research developments to strongly influence the potential of these microbes to promote growth (Moreno-Galván et al, 2020;Cortés-Patiño et al, 2021;Mendoza-Labrador et al, 2021;Pardo-Diaz et al, 2021).…”

Co-Inoculation of Plant-Growth-Promoting Bacteria Modulates Physiological and Biochemical Responses of Perennial Ryegrass to Water Deficit

“…The Pearson analysis showed a moderate (r = 0.4) correlation between total carotenoids and non-photochemical quenching ( Figure 4 ). The higher content of pigments in plants inoculated with the bacterial strains could be associated with their ability to fix nitrogen, as these bacteria have been shown to grow in nitrogen-free medium [ 24 ] and to improve the nitrogen content in perennial ryegrass [ 28 ]. The potential of Herbaspirillum to increase the nitrogen content has also been previously reported in crops like maize [ 29 , 30 ].…”

Phosphate-Solubilizing Bacteria with Low-Solubility Fertilizer Improve Soil P Availability and Yield of Kikuyu Grass

“…AP21 and D7 were isolated from Kikuyu grass, while T88, a symbiotic nitrogen-fixing bacterium, was isolated from nodules of red clover ( Trifolium pratense ). We selected these strains because previous research has demonstrated their ability to promote red clover and ryegrass growth under abiotic stress (drought) conditions [ 24 , 25 ] and to optimize P and N use [ 20 , 26 ]. The guaranteed concentration of each strain was 1 × 10 CFU for strains AP21, T88, and D7.…”

“…These strains were selected because previous studies have demonstrated their ability to promote growth in associated ryegrass and red clover pastures under abiotic stress conditions due to drought [ 24 , 25 ]; in addition, Santos-Torres et al [ 20 ] reported AP21’s capacity to solubilize Pi and T88’s ability to mineralize organic P (Po). Likewise, Pardo-Díaz et al [ 26 ] found that AP21 and D7 showed potential in reducing nitrogen (N) fertilization. In this context, the use of organic and inorganic P sources in combination with PSB has the potential to contribute to increasing soil P availability and improving pasture productivity.…”