Effects Of Boron,Zinc And Manganese On Main Agronomic Characters And Yield And Quality Of Stevia Rebaudiana Bertoni

Stevia rebaudianum Bertoni is a natural sweetener plant.Its glycosides are characterized by high sweetness and low calories,and are attracting more and more attention.At present,the cultivation techniques of stevia are mainly focused on cutting and seedling raising,planting density and the use of macroelement fertilizer,etc.,and there are few studies on the use of microelement fertilizer.The effects of boron,zinc and manganese on the main agronomic characters,yield and quality of stevia were studied by single factor tissue culture test and quadratic orthogonal rotation design.The main research results are as follows:The results showed that the effect of different microelements on the agronomic characters and yield of stevia were different by using single factor tissue culture.The amount of boron,zinc and manganese in the culture medium could promote the growth of stevia tissue culture seedlings,and the most significant influence on the number of buds was Zn3?20mg/L?treatment,with the number of buds of stevia tissue culture seedlings reaching 67.4.The most significant influence on the plant height and rooting rate was Mn4?20mg/L?.The appropriate concentration of boron,zinc and manganese also promoted the synthesis of stevia glycosides.ST content was the highest under Mn3?15mg/L?treatment,while RA and total glycosides content were the highest under Zn3?20mg/L?treatment.The field experiment showed that the application of boron,zinc and manganese could promote the growth and quality of stevia.The effects of zinc fertilizer on the plant height,leaf dry weight,stem fresh weight and yield of stevia were better than those of boron and manganese fertilizer.The effect of boron fertilizer on intercellular CO₂ was better than zinc and manganese fertilizer.B-Zn interaction existed in all the above indexes and they all showed mutual inhibition.Single factor analysis showed that the optimal fertilization range for stevia yield was boron fertilizer 0.8373-0.9765kg/667m²,zinc fertilizer 0.8970-1.0437 kg/667m²,manganese fertilizer0.5658-0.7418 kg/667m².With the increase of the amount of boron,zinc and manganese,the contents of stevioglycan diglycosides,RB,ST,RA and RD all showed a trend of increasing firstly and then decreasing.The optimal fertilizatio n ranges of boron,zinc and manganese were 0.982-1.072,0.624-0.876,0.615-0.739 kg/667m²,0.901-1.099,0.631-0.869,and 0.401-0.599 kg/667m²,respectively,with high-quality glycosides RA and RD as the targets.Combined with the analysis results of the gray relational degree method and DTOPSIS method,the optimal fertilizer amounts of boron,zinc and manganese in stevia field cultivation to gain high quality and yield were finally determined as following:boron fertilizer 1 kg/667m²,zinc fertilizer0.75kg/667m2,manganese fertilizer 0.5 kg/667m².