Novel approaches for understanding and improving the effectiveness of seed biopriming

An 'on-farm' hybrid priming treatment, that combines hydropriming and biopriming with Bacillus subtilis spores was developed for the neglected legumes grass pea, forage pea, and fenugreek. The seed response to treatments highlighted the predominant effect of hydropriming. In the attempt to improve the efficacy of biopriming and enhance the overall value of the combined protocol, an in-depth investigation of the seed-spore interaction was performed. Scanning electron microscopy was used to analyse the seed sculpture roughness. Multispectral imaging analysis was applied to monitor the presence of increasing doses of Bacillus subtilis spores and test the potential of this tool for the optimization of biopriming protocols. Within the wavelengths applied using multispectral imaging, only 645 nm, 660 nm, and 690 nm were able to detect the presence of the spores in the bioprimed seeds, providing a range of analysis potentially effective for discrimination. Grass pea varieties, showing the most contrasting roughness profiles, were selected for multispectral imaging analysis. The investigation highlighted the relevance of the seed sculpture roughness in determining the reflectance of untreated and bioprimed seeds, and the occurrence of variety-specific profiles. Results are discussed in view of the potential use of this model to expand the current applications of multispectral imaging in the context of seed biopriming design.