| Strain Paenibacillus kribbensis PS04,isolated by our team group,was preliminarily demonstrated that metabolites of this strain have broad-spectrum anti-fungal activity.The exopolysaccharide produced by this strain can induce the increase of plant defense enzymes activity.In order to explore the mechanism of PS04 exopolysaccharide induced plant resistance,the effects of PS04 exopolysaccharide on the disease-related genes and resistance related physiological and biochemical substances in rice and tobacco after inoculated with pathogen were studied in the present work.At the same time,the effect of commercial polyfructose(inulin)on rice and tobacco was also studied to compare with PS04 exopolysaccharide treatment group.In addition,the application of PS04 fermentation broth in rice field trials was studied.After rice was inoculated with Rhizoctonia solani,the activity of SOD,POD and CAT enzymes in the PS04 exopolysaccharide-treated group was higher than that in + Rhizoctonia solani treatment,and the maximum values were 1.76,1.66,and 1.77 times as high as the control group,respectively.The activity of catalase in + Rhizoctonia solani treatment had a brief increase in the early period,then decreased lower than in the control group after 5 days.The content of total phenolic and flavonoid in + PS04 exopolysaccharide + Rhizoctonia solani treatment was higher than in + Rhizoctonia solani treatment.The content of MDA in + PS04 exopolysaccharide + Rhizoctonia solani treatment decreased and the chlorophyll content increased,on the contrary,the content of MDA in + Rhizoctonia solani treatment increased and the chlorophyll content decreased.When rice was not inoculated with Rhizoctonia solani,the activity of SOD,POD,and CAT enzymes were increased in the PS04 exopolysaccharide treatment and inulin treatment,and it was higher in PS04 exopolysaccharide treatment.The contents of total phenols and flavonoids in PS04 exopolysaccharide treatment were significantly higher than those in the control group,and the chlorophyll content increased significantly;the MDA content in the two treatments was not significantly different from the control group.After tobacco inoculated with TMV,the activity of SOD,POD and CAT enzymes in the PS04 exopolysaccharide treated group was higher than those in + TMV treament,and the maximum values were 1.83,1.84,and 1.74 times as high as the control group,respectively.In + TMV treatment,the activity of these enzymes increased transiently in the early period,then decreased to be lower than that in the control group after 5 days.The content of total phenols and flavonoids in the PS04 exopolysaccharide treatment was higher than that in + TMV treatment;the chlorophyll content in the PS04 exopolysaccharide treatment group increased while it gradually decreased in + TMV treatment;the MDA content in + PS04 exopolysaccharide + TMV treatment increased more slowly than in + TMV treatment.When tobacco was not inoculated with TMV,the activity of SOD,POD and CAT enzymes increased in the PS04 exopolysaccharide treatment and inulin treatment,and it increased significantly in the PS04 exopolysaccharide treatment.Both of the two treatments the content of total phenols and flavonoids was significantly higher than those in the control group,and the chlorophyll content increased significantly.The MDA content in the two treatments was not significantly different from the control group.The semi-quantitative RT-PCR and real-time fluorescence quantitative PCR were used to detect the expression of PAL,CatA,Rcht,AOS and PR1 a genes.The results showed that PS04 exopolysaccharide could induce the increased expression of disease-resistance related genes in rice.In the PS04-exopolysaccharide-treated group alone,the expression levels of PAL,CatA,Rcht,AOS and PR1 a all showed an increasing trend,and the five diseaseresistance-related genes were rapidly expressed,and their expression levels were mostly higher at the 12-72 h than in the control group.The maximum value was 2.11-22.88 times as high as the control group.Only the group inoculated with Rhizoctonia solani,the expression of resistance-related genes increased slowly.In PS04 exopolysaccharide + Rhizoctonia solani treatment,the expression of PAL,CatA,Rcht,AOS,and PR1 a genes increased rapidly compared with the only inoculated with Rhizoctonia solani treatment,and the expression level was significantly higher than that of the control group.The maximum value was 4.30-25.04 times as high as the control group.In the inulin-treated group alone,the expression of resistance-related genes increased but not significantly.The semi-quantitative RT-PCR and real-time fluorescence quantitative PCR were used to detect the expression of resistance genes PR1 a,PR1b,NPR1,MAPK and N in tobacco.The results showed that PS04 exopolysaccharide could induce the increased expression of disease-resistance related genes in tobacco.In the PS04-exopolysaccharide-treated group,the expression levels of PR1 a,PR1b,NPR1,MAPK,and N genes all showed an upward trend,and the five diseaseresistance-related genes were rapidly expressed,and their expression levels were mostly higher than in the control group at the 12-72 h.The maximum value was 3.72-14.46 times as high as the control group.In the group treated with TMV only,except that PR1 b gene expressed more rapidly,the expression of other disease-resistance-related genes increased slowly.In PS04 exopolysaccharide + TMV group the expression of PR1 a,PR1b,NPR1,MAPK,and N genes increased more rapidly compared with the inoculated with TMV group,and the expression level was significantly higher than that of the control group.The maximum value was 4.74-47.43 times as high as the control group.In the inulin-treated group alone,the expression of resistance-related genes increased but not significantly.The results of application of PS04 fermentation broth in Jangmen rice field experiments showed that the control effects of PS04 fermentation broth on early and late rice sheath blight in 2016 and 2017 years were 57.61%,67.88%,35.74% and 56.90%,respectively.The 1000-grain weight of rice in the PS04 fermentation broth treatment was higher than that in the control group,which increased by 2.12 g,0.72 g,1.45 g,and 1.52 g,respectively.Except that there was no significant difference between PS04 treatment and the control group of early rice in 2017 year,the seed setting rate of the PS04 treatment was significantly higher than that of the control group(p<0.05).The yield of rice treated with PS04 fermentation broth was 13.43% higher than that of non-sprayed PS04 fermentation broth.The results of application of PS04 fermentation broth in rice field experiments in Jangxi province showed that PS04 fermentation broth can reduce the damage of sheath blight and increase rice yield. |
