Trichoderma koningiopsis Survival on Coated Seeds and Effect on Plant Growth Promotion in Rice (Oryza sativa).

Seed coating is an alternative delivery system for beneficial plant microorganisms into the soil. Although seed coats are widely used for the application of agrochemicals, the incorporation of beneficial microorganisms has not been explored deeply and their survival on seeds while in storage is unknown. The study aimed to evaluate the effect of the coating process on microbial survival and on plant growth promotion. Two coating formulations were designed, and assessed by two coating processes: rotating drum and fluidized bed. The rotating drum process resulted in more uniform coatings than in the fluidized bed process. In addition, with this coating technique, lower viability losses over time were observed. The rotatory drum prototype containing a biopolymer and a clay mineral derivate (P90) showed the best behavior at the three temperatures evaluated, with superior viabilities compared to the other prototypes and the lowest loss of viability after 12 months. The formulation of this coating prototype may preserve the viability of Trichoderma koningiopsis Th003 up to 15 months at 8 °C, 9 months at 18 °C, and 3 months at 28 °C, which are very promising shelf-life results. Regarding the effect of seed coating on plant growth, prototypes showed higher yields > 16% than the control, comparable to the conventional use of Tricotec® WG, which may reduce the number of applications and water consumption for dissolution of the inoculant. The results demonstrated that the formulation composition, as well as the coating process may impact the microbial survival on seeds.

Seed coating as a delivery system for the endophyte Trichoderma koningiopsis Th003 in rice (Oryza sativa).

Seed coating is a technique to cover seeds with external agents to upgrade their performance, handling, and plant establishment. Plant beneficial microbes (PBMs), such as plant growth-promoting bacteria, mycorrhizal fungi, and other fungi (e.g., Trichoderma spp.), decrease agrochemical inputs, enhance tolerance to biotic-abiotic stresses, and increase essential plant nutrition. The demand for pre-treated seeds as delivery systems for biological agents is advancing. Here, a seed coating formulation containing Trichoderma koningiopsis is presented. The physicochemical and biological characterization of the seed coating prototypes included drying protector screening, the effect of the inoculum concentration on survival, the assessment of microbial release profiles in soil extract, and plant tissue colonization capability under semi-controlled conditions. Gelatine and pectin, two of the tested drying protectors, maintained fungus germination after 60 days at 18 °C with significantly higher values of up to 38% compared with the control. The initial concentration of 106 colony-forming units (CFU) per seed undergoes a positive effect on survival over time. Regarding plant tissue colonization, the fungus establishes endophytically in rice. In conclusion, seed coating is a promising alternative for the formulation of beneficial microbial agents such as Trichoderma sp., maintaining cell survival and further promoting the establishment in rice systems.Key points• Enhancing drying survival of T. koningiopsis formulates• Seed coating formulation approach for T. koningiopsis in rice• Colonization capacity of formulated T. koningiopsis in rice tissue.