| Rice false smut is a fungal disease caused by Villosiclava virens,which attacted rice stamen filaments at booting stage,and has now developed into a major rice disease in China.Under the conditions of artificial inoculation,most of the rice varieties showed high degree of disease,but the disease resistance between the varieties was significant under the natural pathological conditions in the field.To this end,we conducted a comparative analysis of the agronomic traits of panicles in rice varieties with significantly different disease resistance in the field.Through the determination and analysis of agronomic traits of different rice varieties at different stages of booting stage,the results showed that there were significant differences in leaf area,perimeter of spike sheath,overlapped leaf sheath at the thickest part of spike sheath,angle of leaf sheath,spike length and grain density between susceptible and resistant varieties.Among them,the difference of panicle traits is particularly obvious.Compared with resistant varieties,susceptible varieties have poor hermeticity of panicle sheath,which results in large area of Rice Panicles exposed to air at the optimum period of rice false smut fungus infection,and directly promotes the occurrence of disease and aggravates the severity.This important characteristic is closely related to the differences of panicle traits mentioned above.In addition,we found that the leaf angle and perimeter of the sheath at the thickest part of sheath were not related to the severity of the disease.The occurrence of rice false smut is largely affected by climatic factors.In the rice booting stage,the prevention and control of bactericides is often caused by continuous rain.To this end,two biocontrol fungal strains that can infect and degrade rice false smut balls are also screened,namely Gliocladium roseum and Bionectria ochroleuca.After 25 days of inoculation,the mycelium of the Gliocladium roseum could completely enclose the rice false smut balls,and the 40 days rice false smut balls completely degraded.The Bionectria ochroleuca can enclose the rice false smut balls after inoculation for 10 days,and degrade that at 10-15 days,This means its degradation ability is the best.Ultrastructural observations showed that the hyphae of Gliocladium roseum and Bionectria ochroleuca grow along the intercellular space of the rice false smut balls,and insert into hyphae cell through the hyphae cell wall.And it can also penetrate the inner and outer wall of the chlamydospores,gradually degrades the hyphae cell and destroys the spore structure,and finally degrads the cell wall of the rice false smut.At the same time,the Gliocladium roseum suspected to secrete enzymes or antibiotics,and the bio-control mechanisms of these two strains are similar to myco-parasitism.Field control experiments showed that only Gliocladium roseum has obvious control effect on rice false smut balls,and the control effect is 16.3%.Using plate sputum method to explore the inhibitory effect of two strains on the growth of rice false smut fungus.The results showed that the two strains had the same inhibiting effect on the growth of rice false smut fungus.after 15 days of co-cultivation,the hyphae of V.virens is no longer grows,and the 20-day biocontrol strain overgrown the whole culture medium.From the Colony morphology,the growth of the hyphae of V.virens can be inhibited by the biocontrol agent by continuously cultivating the nutrients in the medium competing with the V.virens and absorbing the nutrients of V.virens. |
