Studies On Shoot-Tip Micrografting For Virus Elimination

The study was carried out with citrus mature stem segments of Bendizao mandarin(Citrus reticulata), Satsuma mandarin (C. unshiu), Hongyugan tangor [C. reticulatax (C. sinensisxC. reticulata)] as explants. The in vitro induction system for adventitious buds was established, and then with these buds, shoot-tip micrografting was performed and plantlets were obtained. Finally, virus detection of these plantlets was carried out by PCR. The main findings are as follows.1. Different disinfection methods were compared and a best disinfector was screened out, which markedly reduced the contamination rate of mature stem segment explants. It was ob-served that for a sunny day in summer, with mature, half lignified stem segment explants ex-cised after2p.m., and with a disinfection protocol of48h interval, the contamination rate was22.53%, and survival rate was the highest.2. Plant hormone concentration combinations of6-BA, IAA and GA3were tested, and it was found that the combination0.5mg/L6-BA+0.05mg/L IAA+1.0mg/L GA3was best for in vitro induction of adventitious buds from the stem explants.3. Shoot-tips from different sources were compared as regarding to micrografting survival rate, and it was found that the in vitro cultured adventitious buds are better than the buds directly collected from field trees, for having a survival rate of73.5%, as compared with51.6%of the latter, buds from field trees of micrograftin survival seedling grew better than that of in vitro cultured adventitious buds of micrografting survival seedlings, It can be considered to7-8months in the field of newborn tender tip with stem tip micrografting, which can effectively guarantee the quality of micrografting; Others specific provisions of a few months from in vitro regeneration tender tip take stem tip for micrografting which can effectively prolong graft cycle.4. PCR primers were designed based on the sequence of citrus huanglongbing virus nucle-otide, Through PCR, virus was not found on the plantlets from shoot-tip micrografting while the filed plants, were swell to the specificity of1is greater than703bp band, with3-4leaf primor-dium shoot-tip micrografting survival seedling bud grafting, no to a specific bands, showed that test of different varieties of citrus plant is poisonous, through the shoot-tip micrografting itwas successful removal the citrus huanglong virus, Therefore, it can be concluded that virus free plantlets can be obtained through shoot-tip micrografting on citrus, and the techniques estab-lished here are valuable for industrial application.