The resistance of Stylosanthes guianesis to Colletotrichum gloeosporioides induced by methyl jasmonate and K2HPO4

The effects of methyl jasmonate (MeJA) and K2HPO4 on induced resistance of Stylosanthes guianesis cv CIAT184 to Colletotrichum gloeosporioides were studied. The results indicated that the disease indexes of S. guianesis decreased significantly (P0.05) by treatments of MeJA with concentration ranged from 0.001 to 0.1 mgmL-1 and K2HPO4 with concentration ranged from 10~50 mmolL-1. The optimal concentration of MeJA and K2HPO4 treatment was 0.001 mgmL-1 and 30 mmolL-1, respectively, which had induced effects of 64.84% and 54.40%, respective. The activities of POD and PPO in plants treated with 0.001 mgmL-1 MeJA increased and reached maximum at 48 hour after inoculation, which were significantly (P0.05) higher than those in control plant without MeJA. The activities of POD and PPO in plants treated with 30 mmolL-1 K2HPO4 increased and reached maximum at 48 hour and 24 hour after inoculation, respectively, which were significantly (P0.05) higher than those in control plants without K2HPO4. These results suggested that MeJA and K2HPO4 increased the activities of antioxidant enzymes like POD and PPO in the early stage after inoculation to improve the resistance of S. guianesis to anthracnose after inoculation. The activities of CAT in plants treated with 30 mmolL-1 K2HPO4 increased from 48 hour to 72 hour after inoculation, which were significantly (P0.05) higher than those in control plants without K2HPO4. However, the activities of CAT in plants treated with 0.001 mgmL-1 MeJA were similar with those in control plants without MeJA excepted with the former one was significantly (P0.05) lower than later one at 72 hour after inoculation. These results indicated that the induced effects of these two chemicals on the disease resistance of S. guianesis to C. gloeosporioides were related with the activities and induced time of POD, PPO and CAT.