| In the introduction and cultivation of medicinal plants, chemical pesticides were mainly used toprevent the hazards of a variety of diseases and insect pests. Due to excessive or improper application ofpesticides, the pesticide residues usually surpassed its maximum limit, and resulted in new threats tohuman health besides disease prevention and control. At the same time, the quality of herbs (it mainlydepends on the content of active ingredient) and the level of security (pesticide residues) have become a"bottleneck" restricting the development of medicinal plants. In this study, we used5-6-year-oldSchisandra picked in the Schisandra experiment Park of Institute of Special Wild Economic Animalsand Plants, CAAS, as experimental materials. Many parameters were measured during different periods(The content of soluble sugar, acid, tannin, color value, and the active ingredient), to master thedynamic developing process of Schisandra. We also analyzed the influences of different Schisandravarieties, management levels, ages and rough working methods on the content of the main componentsof lignans (Schizandrol A, schizandrin A, Schizandrin B). By measuring the TM residues of Schisandathat underwent different spraying processes and combined with the field condition survey, we raised asafe and effective method to control the powdery mildew. The main conclusions are as follows:1. The content of soluble sugar, titratable acidity, and color value were increasing during thegrowth phase of July20to September10. On the contrary, the content of tannin was declined. Thecontent of soluble sugar, titratable acidity, tannin, color value were tend to be steady from September.2. The optimum extraction process of lignans were as follows: ethanol concentration81.22%, ratioof solid to liquid1:8.26, ultrasonic time33.11minutes, ultrasonic temperature39℃. As a result, thetheoretical value of schisandra lignans could reach1.575%. In actual operation process, we also couldchoose the conditions of ethanol concentration81%, solid-liquid ratio1:8, ultrasonic time33minutes,ultrasonic temperature39°C, ultrasonic extraction three times.3. The contents of lignans in Schisandra showed significant difference among20differentgermplasms (P<0.05). The better the cultivation and management conditions were, the higher lignanscontent would be. As the lignans content reduced gradually along with processing temperatureascending, the drying temperature should not exceed50°C.4. According to the characteristic of high pigment content in Schisandra, based on GB/T5009.188-2003, we used V (petroleum ether): V (iso-octane)=5:1mixed solvent (25mL) for extractiontwice, and this could remove pigment effectively, thus established a suitable method for measuring TMresidues.5. In the growth period, powdery mildew could be prevented effectively by spraying500~1000fold TM solvent4to6times. The disease incidence was26%~35%when praying1500fold TM4~6times, and the disease index was12.5%~17.8%. However, the powdery mildew increased sharply withno defense performed, and the disease index reached67.5%~69.6%. We believe that during the growthperiod (mid-June),800~1000fold TM is the optimal consistency for preventing powdery mildew, andspraying4times are needed. 6. In the fruit growth period, pesticide residue increased gradually along with the sprayingfrequency when500fold TM was sprayed4~6times, about0.077mg/kg~0.198mg/kg. The pesticideresidue was0.111mg/kg~0.149mg/kg when spraying1000fold TM6times (10days to harvest), and0.063mg/kg~0.093mg/kg when spraying1500fold TM6times (10days to harvest). No pesticideresidue was detected if1000~1500fold TM was sprayed4~5times (20~30days to harvest).7. Combined with the disease index survey results, we believe that powdery mildew can beprevented by spraying1000fold TM every13~15days during fruit growth period (mid-June to August20), and green herbs standards can be easily reached. |
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