Studies On The Rapid Propagation Technical System Of Virus-free DangShan Pear Via Meristem Culture

The yield and quality of pear are greatly taken from virus desease as viruses infecting and accumulating in the pear tree while continually asexual propagation. One of the best measures is selecting virus-free plants through meristem viruses elimination to treatment pear virus desease at present. The research reported four different virus elimination methods, virus detection techniques, rapid propagation system of virus-free plant and genetic stabilityof pear of continous generational culture. The results are as follows:Growing buds in early May as explant would be easy to get the lowest contaminating rate, high surrival rate, better gemernation and high virus elimination rate. Growing buds in early May as explant with some measures of browning controlling can reduce browning rate to 5.7%.Culture media are seleted by L9(34) orthogonal design and single factor experiment. The results showed the optimum medium for shoot tip differentiation inducting was the improved MS medium with BA 2.0mg/L, NAA 0.5 mg.L-1. However, MS medium with high mineral salt concentration is favorable to the growth of virus-free test-tube plantlet. Effects of exogenous hormones on the shoot propagation and the growth of the bud and for endogenous hormones in the course of tube plantlet subculture indicated that the content of endogenous ZR and the shoot effective proliferation were increased while the value of IAA/ZR and the height of the plantlet decreased markly after BA treated. Exogenous NAA showed significant effective on the amount of endogenous IAA and the height of plantlet. There are positively relative between the height of plantlet and the amount of IAA and IAA/ZR. Exogenous NAA and GA also revealed stimulating rule for content of endogenous IAA and GA1+3. The optimum time of subculture for virus-free plantlet is 45 days. In theory, 4.06 × 106 times of tube plantlets per year can be obtained from one virus-free pear shoot through rapid propagation.In rooting stage, we tested the effects of factors such as PG, IBA NAA and content of basal medium. The results showed that their effect is PG > IB A > NAA > content of basal medium. Two steps rooting method was more efficient and practical than direct rootingmethod with rooting rate 87.5%. Higher concentration of IDA was needed for rooting. Aditionally rooting out of vessel technique was studied. Though the plantlets rooting rate out of vessel was very low, it could save production cost. The acclimatization of plantlets is important before transplanting.Four methods (meristem culture, re-meristem-culture, meristem culture combining with heat treatment of constant temperature and variation temperature) for eliminating viruses have been compared. The examining result by ELISA showed that meristem culture combining with heat treatemnt of variation temperature is the most efficient for the elimination rates of apple stem grooving virus.Herbaceous indicators and ELISA were applied in detecting virus elimination of tube plantlet. By analyzing, we drew a conclusion that Dangshan pear carried apple stem grooving virus and other viruses and unearned TMV.The isozyme analyzing results showed that there are no change on band number of the peroxidase and estarase isozyme between virus-free plants and the contrast, which confirmed the genetic stabilities of Dangshan pear and virus-free plantlet.