Biopolymers for biopriming of Brassica rapa seeds: A study on coating efficacy, bioagent viability and seed germination

The coating agent is critical in ensuring the success of seed biopriming. In this study, various biopolymers (sodium alginate, carboxymethylcellulose, gum arabic, xanthan gum) were tested for their efficacy as a coating agent for bioagent (Trichoderma asperellum) bioprimed to Brassica rapa (pak choy) seeds. Seeds and bioagent were first treated separately in biopolymer solutions, and examined for seed germination and spore viability, respectively, as a measure of compatibility. The suitable biopolymers and concentrations were then used to coat T. asperellum to the seeds, and the percentage of spore entrapped, and viable spore count were determined to reflect coating efficacy. The biopolymer with efficient coating efficacy was selected and employed as coating agent with various spore concentrations on seeds, and seed germination and radicle length were determined. Results revealed that coating with biopolymers benefited seeds. Spore viability was higher when treated with all biopolymers (89–100%) than without (84%). Higher coating efficacy was achieved with sodium alginate (1.5% w:v) which entrapped more spores during biopriming (83.63 ± 0.86%) and retained more viable spores (4.01 ± 0.01 log spore seed^-1) after 24 h post-priming. Biopolymers have no adverse effect on radicle length and seed germination, although increasing spore concentrations inhibited radicle elongation. In short, biopriming using sodium alginate (1.5% w:v) with 10² spores/mL of T. asperellum is therefore recommended for Brassica seeds as higher seed germination (90.67 ± 2.88%) and overall benefits can be achieved.