The Preparation And Immune Protective Efficacy Of Novel Bivalent Vaccines Of Porcine Reproductive And Respiratory Syndrome Virus And Porcine Circovirus Type 2

Cabbage(Brassica oleracea L.var.capitata L.)belonging to Brassica of Cruciferous,is orginated from Mediterrance to the North Sea coast.Cabbage has been widely cultivated all over the world.Because of it's rich nutrition,diverse edible ways and large production area,cabbage has high economic and edible value.It usually takes a long period of time from collection to sowing.Due to natural aging or inappropriate storage environment,seed vigor will be getting lower and lower.Seed vigor has an impact on seed germination,seedling emergence and growth.Seed priming technique can improve seed vigor and resistance ability to stress after germination.In this study,two cabbage cultivars 'Sugan 27' and 'Bochun' were selected as experimental materials.Different concentration of PEG,Ca(NO3)2,SA were selected as chemical initiators to study the effects of single or combined priming treatments on cabbage seed germination and physiological characteristic,and high temperature-resistance,and to explore the influence of different storage temperature on the seed germination and physiological characteristic of primed and non-primed seeds,which can provide theoretical basis for the application of priming treatment in cabbage cultivation.The main results were as follows:1.Three different concentration of chemical initiators could improve the germination rate,germination energy,germination index and vigor index,decrease the average germination time,increase the activity of antioxidant enzyme,so as to slow down the damage caused by lipid peroxidation of membrane structure and function.The priming treatments also could decrease the relative conductivity and increase the content of soluble sugar and protein,which providing better conditions for seed germination.By the comprehensive comparison of various parameters,it is found that the best concentration of PEG-6000 was 2×105mg·L-1,Ca(NO3)2 was 2×103 mg·L-1,SA was 50 mg·L-1.2.Seed priming treatments could improve the seed germination characteristics,the emergence and growth index.Under high temperature stress,seed priming treatments improved the activity of antioxidant enzymes,reduced the injury of cell membrane and the accumulation of MDA,the increase of relative conductivity because of the high temperature stress.Meanwhile,seed priming treatments also raised the root activity,chlorophyll content when under high temperature.Taken together,different seed priming treatments can enhance the seed vigor and the heat resistance of seedlings.Among the priming treatments,the mixture priming treatment(2×105 mg·L-1 PEG:2×103 mg·L-1 Ca(NO3)2:50 mg·L-1 SA=1:1:1)had the best effect.3.After 120 days of storage at different temperature,the cabbage seed germination characteristics,soluble sugar content and a-amylase activity of the primed seeds decreased,and the accumulation of MDA also increased,resulting in the the injury of cell membrane and the growth of seedlings was restrained.Primed seeds of 25? storage significantly reduced the seed vigor.However,primed seeds of 4? and-20? only had a slightly reduced seed vigor,and the seed vigor was higher than non-primed seeds.It suggested that seed priming could improve cabbage seed vigor,but primed cabbage seeds were unfavorable for storage at room temperature.Moderate cryopreservation could maintain moderately higher seed vigor,and storage under 4? and-20? storage had a similar effect.In addition,after 120 days of storage at different temperature,the seed vigor of non-primed seeds didn't have a significant difference.