Synergistic Effect of Brassinosteroid and Jasmine Extract on Promoting Rice Ratooning Ability

Ratoon rice cultivation is a significant practice for enhancing land productivity and food security. Ratooning ability is a key determinant of ratoon season crop (RC) yield and is influenced by genetic, agronomic, and hormonal factors. This study aimed to evaluate the effects of foliar-applied ratooning enhancers, formulated with plant hormones and botanical extracts, on the growth and regeneration of a japonica-indica hybrid rice cultivar, 'Qingxiangyou 19 Xiang'. Treatments included gibberellin (GA), low, medium, and high concentrations of brassinosteroid (BR), each with or without jasmine extract (JE), alongside proline and zinc chloride (ZnCl₂) as supporting components. These solutions were applied twice at 5 and 15 days after flowering (DAF) of the main crop (MC). The results showed that GA treatment increased plant height and panicle length but reduced MC tiller number. BR treatments did not affect plant height but significantly increased the 1000-grain weight. Crucially, while BR alone had no significant effect on ratooning ability, the BR-JE combined application, particularly at medium (MBR-JE) and high (HBR-JE) concentrations, significantly increased ratoon tiller number and enhanced ratooning ability. However, the HBR-JE combination increased grain chalkiness. In conclusion, the foliar application of BR combined with JE during the flowering stage effectively promotes ratooning ability without compromising MC yield, offering a promising agronomic strategy for sustainable ratoon rice production.