Preliminary Study On The Mechanism Of Silicon Induced-resistance Of Rice To Defense Against Root Knot Nematode Meloidogyne Graminicola

Meloidogyne graminicola is an important pathogenic nematode on rice production,and it seriously threatens the safety of rice production.As a kind of inducing factor,silicon has been paid more and more attention to the role of plant resistance to biotic stress and abiotic stress.Silicon-induced rice defense disease research reports mainly focus on rice blast,sheath blight,rice bacterial blight and other fungal and bacterial diseases,but for silicon-induced rice defense against M.graminicola research rarely reported.In this paper,we used different fertilizer treatment conditions to examine the effects of silicon on the growth of rice,the effect of silicon fertilizer on the resistance of rice to M.graminicola,the effect of silicon fertilizer on the induction of rice-related defense substances,and the real-PCR was used to analyze the effect of silicon fertilizer on the induction of rice-related defense gene expression,and to clarify the mechanism of silicon-induced rice defense against root-knot nematode resistance.Application of 0.375g/L silicon fertilizer with soil is the optimum treatment of silicon-induced resistance of rice to defense against M.graminicola.Compared with the solution of silicon treatment,the effect of silicon fertilizer with soil on the growth and development of rice was more significant.Compared with the control group,the rice plants treated with 0.375g/L of silicon fertilizer and the substrate had the best resistance to root-knot nematode,and the number of root knots and the number of infected nematodes decreased by 57.7%and 56.7%.The content of silicon,hydrogen peroxide,lignin and soluble phenol in rice roots were significantly increased by the determination of the content of related defense substances in rice roots.The treatment of silicon fertilizer could significantly increase the content of hydrogen peroxide in rice roots was significantly increased at 6h after inoculation.The treatment of silicon fertilizer could significantly increase the content of lignin and soluble phenol in rice roots at 24h and 48h after inoculation.The related defense genes in rice roots were analyzed by fluorescence quantitative PCR showed that silicon fertilizer could induce the up-regulation of SA signal pathway and ET signal pathway in rice.The relative expression of SA biosynthesis genes?OsPAL1,OsICS1?was significantly up-regulated in the silicon treatment plants at 24h and 72h after inoculation respectively,and the relative expression of SA signaling pathway transcription gene OsWRKY45 was significantly up-regulated at 6h after inoculation.The relative expression of ET biosynthetic gene OsACS1 in the silicon treatment plants was significantly up-regulated at 6h and 72h after inoculation,and the relative expression of ET signaling pathway gene OsERF1 and OsEIN2 was significantly up-regulated in the silicon treatment plants at 24h after inoculation.The relative expression of C4H biosynthetic gene OsC4H was significantly up-regulated in the silicon treatment plants at 6h after inoculation.The relative expression of lignin synthetic gene OsCAD6 was significantly up-regulated in the silicon treatment plants at 72h after inoculation.In the silicon treatment plants,the relative expression of H₂O₂ synthesis gene OsRbohB and callose synthesis gene OsGSL1 at 72h after inoculation.Based on the root gall index and the number of nematodes inside the roots,the present research evaluated resistance/susceptibility to M.graminicola of different subpopulations of Oryzae sativa in pot and field experiment.Investigation of the randomLy selected varieties revealed that the number of nematodes inside roots correlated very strongly?r=0.87,P<0.05?with the nematode gall index.Results in pot and field experiment showed a similar ranking of the varieties for susceptibility/resistance against this nematode.Out of the 136 tested varieties,Zhonghua11,Shenliangyou1 and Cliangyou4418were proved highly resistant to M.graminicola under both pot and field conditions.Further research on the nematode development suggested that nematodes penetrated less inside of highly resistant varieties but failed to develop into females more than that of susceptible control.In summary,We have clarified the mechanism of silicon-induced rice defense against root knot nematode Meloidogyne graminicola.This study laid a foundation for deeply understanding of silicon-induced resistance mechanism of nematode disease,and provided a theoretical basis for better use of induced resistance to control nematode disease.In addition,we found that the three rice cultivars Zhonghua 11,Shenliangyou 1 and C Liangyou 4418 showed high resistance to the root-knot nematode,and provided the experimental basis for the breeding of resistant varieties of rice.