Elicitor activity of algino-oligosaccharide and its potential application in protection of rice plant (Oryza saliva L.) against Magnaporthe grisea

Rice blast caused by Magnaporthe grisea is considered to be one of the most devastating diseases in most rice-growing regions. In order to search for an effective agent to protect against rice infection, the elicitor activity of algino-oligosaccharides was evaluated in germinating rice, in which accumulation of oryzalexin C could be detected sensitively. The maximal elicitor activity was detected in germinating rice seedlings when the fractions of alginate degradation products with a degree of polymerization of 7.9 (S3) and 6.5 (S4) were used as elicitors. Algino-oligosaccharides could induce the enzyme activities of phenylalanine ammonia lyase, peroxidase and catalase in rice plant cells for protection of the plant against the invading pathogen. With utilization of algino-oligosaccharides, the disease index caused by Magnaporthe grisea could be reduced from 17.74% to 10.81% and the protection efficacy was 39.06%. These findings suggest that algino-oligosaccharides could be applied as a biological agent to control rice blast disease.