Mechanisms Of Resistance Induced By Jinggangmycin-A On Rice Sheath Blight

Jinggangmycin A(J-A)has been well known as an antibiotic to control rice sheath blight caused by Rhizoctonia solani Kiihn AG-1IA. It is a secondary metabolite from streptomyces with antifugal activity against plant pathogens, it does not kill the fungi , but causes growth anomalies decreasing their virulence. The control activity of J-A could keep for about 2 weeks on rice and decreased after treatment for 21days.What is the reason why it can keep so long ? There are at least two approaches:one is the direct antagonistic action to inhibit the growth of pathogenic fungi;the other is systemic resistence of host plant stimulated by J-A treatment.The concentration (1. OM-g/ml )that could not inhibit the pathogen growth directly showed an effective control activity on sheath blight in field. Moreover ,there was no manifest difference on control effect occurred in the field trail that treated with 15.0 M-g/ml and 25. OM-g/ml of J-A. We proposed that the 15.OM-g/ml was possible to be accepted as a practical concentration.The contents of soluble suga in rice flag leave after spraying J-A was significantly increased. The activity of chitinase and β-1 , 3-glucanase in rice flag leave wereanalysised after J-A treatment on rice. The result showed that activity of chitinase and 6-1 , 3-glucanase both increased in different degrees than water - controlled treatment and reached the peak after treated 7days and 3 days respectively. Changes of contents of trehalose and activity in rice flag leaves were studied. Contents of trhalose were significantly increased after 3 days Jinggangmycin A treatments, activity of trehalase in rice flag leaves was significantly inhibited. The correlation between trehalose and trehalase activity is clear.