| Bayberry?Myrica rubra?is a plant of Myricaceae,one of the characteristic fruit tree in Zhejiang Province.The cultivated area is more than 1.3 million mu,with an annual output value of more than 5 billion yuan.Bayberry twig blight is a major disease that harming the growth of bayberryin recent years.The pathogens of bayberry twig blight were Pestalotiopsisversi color and P.microspora.Paclobutrazol is a new,efficient and low toxicity triazole plant growth retardant,which is mainly used to promote flower bud differentiation of`Dongkui'bayberry.In this paper,‘Dongkui'variety was used as the test material to clarify the effect of different concentrations of paclobutrazol on the occurrence of the bayberry twig blight,The effects of different concentrations of paclobutrazol on the growth,physiological and biochemical characteristics and gene expression of bayberry twig blight were studied.The main results are as follows:1.The growth of twig blight pathogen was inhibited by 150 mg·L-1,300 mg·L-1,450 mg·L-1 and 600 mg·L-1 concentrations of paclobutrazol.The inhibition rate of paclobutrazol treatment on mycelial growth was 62.62%-82.06%,and the relative inhibition rate of spore germination was 43.08%-81.76%.The effects of different concentrations of paclobutrazol on the extracellular enzyme activities of pathogenic fungi were different.Compared with the control,the activity of pectinase increased by 7.5%-140%in the treatment of paclobutrazol,and there were significant differences between the treatment of 150 mg·L-1 and 300 mg·L-1 paclobutrazol and the control.The activity of carboxymethyl cellulase increased by 366.2%-568.0%compared with the control,and the difference was significant.The amylase activity of paclobutrazol treatment decreased by 11.5%-68.8%compared with the control,and the inhibition increased with the increase of paclobutrazol concentration.2.After treating the branches of bayberry with concentrations of paclobutrazol(0 mg·L-1,300 mg·L-1,600 mg·L-1 and 900 mg·L-1)for 15days,the results showed that the leaves of bayberry treated with paclobutrazol turned brown gradually from the old leaves at the bottom of branches to the tender leaves at the top,and the damage degree of leaves increased with the increase of paclobutrazol concentration.The production of reactive oxygen species?ROS?,the degree of membrane lipid peroxidation and the scavenging system of ROS in the leaves of bayberry were detected at the time points?24 h,30 h,36 h,48 h,72 h,96 h?after pre-culture with paclobutrazol solution for 1 day.Paclobutrazol could inhibit the production of superoxide anions.Low concentration of paclobutrazol treatment(300 mg·L-1 and 600 mg·L-1)could significantly reduce the content of H2O2 and MDA.High concentration of paclobutrazol(900 mg·L-1)could damage plants in the treatment period,and its content was higher than that of control.Paclobutrazol treatment canincrease the activity of SOD,POD,CAT and APX and the content of ascorbic acid in varying degrees,among which 300 mg·L-11 and 600 mg·L-1 paclobutrazol treatment has obvious effect.3.Bayberry inoculated with twig blight pathogen were cultured in concentrations of paclobutrazol solution containing 0 mg·L-1,300 mg·L-1,600 mg·L-1 and 900 mg·L-1 for 15 days,the results showed that in the presence of paclobutrazol,the incidence of bayberry twig blight was rapid and serious.Paclobutrazol treatment could alleviate MDA and superoxide anion production in leaves of bayberry in varying degrees,and 300 mg·L-1 and 900mg·L-1 paclobutrazol treatment significantly reduced the content of H2O2 with 30-48 h.The effects of different paclobutrazol treatments on plant active oxygen scavenging enzymes and antioxidants were different.The overall manifestation was that paclobutrazol treatment could significantly increase the activity of active oxygen scavenging enzymes in a short time?24-36 h?,and the effect of paclobutrazol treatment on increasing the content of antioxidant ascorbic acid was obvious in 96 h.4.When treated with paclobutrazol,the results of RT-qPCR showed that the expression of HMGB9 gene increased after 300 mg·L-11 and the expression of HMGB9,WRKY40 and MADS-box protein genes increased after 600 mg·L-11 treatment,while the expression of WRKY40 gene increased after 900 mg·L-1 treatment.When treated with paclobutrazol and bayberry twig blight pathogen,the expression of HMGB9 gene was higher under 300mg·L-1 treatment than that of the control.The expression of MAPKK4,MADS-box protein and HMGB9 gene were higher under 600mg·L-11 treatment than those of the control.The expression of SBPase and MAPKK4 gene were higher under 900 mg·L-1 treatment than those of the control.With the increase of treatment time,the expression of WRKY40and MADS-box protein gene were higher in 24-72 h than that in control,and decreased in 96 h. |
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