Abstract:

Pelletized seed coatings reduce the incidence of pests and diseases， protect seeds against drought stress during direct seeding， and improve the precision of sowing， ensuring healthy seedlings. The aim of this study was to identify the most suitable formulation of pelletized seed coating for three typical varieties of brewing sorghum （Sorghum bicolor） cultivars： Jinnuoliang No. 9， Lunuo No. 8， and Hongyingzi. Different additives including fillers and pelleting aids （gum arabic and diatomite）， bioactive substances （the fungicide tebuconazole， the insecticide cyantraniliprole， and the plant growth regulator brassinolide） and functional materials （alginic acid， a super absorbent polymer water retention agent） were combined to create seed coatings. Then， the effects of seed coatings with different formulations on the seed germination and seedling growth of the three sorghum cultivars were investigated in an indoor germination test and a hole tray sowing test. The results showed that a combination of diatomite as the filler and a 15% solution of gum arabic as the bonding agent had a minimal impact on seed germination across the three sorghum varieties when pellets were 5 mm in size. The seed coating agent disintegrated rapidly and there was a high proportion of single-seeded pellets， which contributed to its superior result. The seed coating containing fungicide∶insecticide∶plant growth regulator at a 1∶1∶1 ratio as the bioactive ingredients significantly improved the seed germination rate and the seedling plant height and root length. Specifically， the application of this seed coating ingredient to seeds of Jinnuoliang No. 9， Lunuo No. 8， and Hongyingzi increased the germination rate by 4.6%， 3.1%， and 6.3%， respectively， increased the seedling height by 11.0%， 19.0%， and 38.1%， respectively， and significantly increased the root length by 18.9%， 50.7%， and 100.5%， respectively. Including an appropriate concentration of alginic acid in the seed coating also effectively promoted sorghum seedling growth. Specifically， alginic acid at a concentration 0.1% in the seed coating significantly improved Jinnuoliang No. 9’s seed germination rate by 9.6%， plant height by 32.5%， and root length by 130.9%. Alginic acid at a concentration of 0.3% in the seed coating agent achieved the best results for Lunuo No. 8 and Hongyingzi， significantly increasing their germination rate by 11.8% and 19.7%， plant height by 37.6% and 63.9%， and root length by 113.2% and 156.3%， respectively. The optimal pellet size for sorghum seeds was 5 mm， and the best seed coating formulation was 37.5% diatomite， 9.42% gum arabic， 13.27% alginic acid， 13.27% fungicide， 13.27% insecticide， and 13.27% plant growth regulator. The most effective alginic acid concentration was 0.1% for Jinnuoliang No. 9， and 0.3% for Lunuo No. 8 and Hongyingzi. The results of this research provide scientific data to underpin the development of practical guidelines and technical support for pellet-seeding of brewing sorghum in Southwest China.

Key words: pelletized seed coating agent, brewing sorghum, seed germination, seedling growth