Study On The Technique System Of Micropropagation In Pomelo

On the one hand, sterile plantlets of mature embryo of sour pomelo and ZhongJiang pomelo were used for experimental materials to study the most suitable explant type, media and transplanting condition in the establishment of an efficient in vitro plant regeneration system of pomelo seedlings. On the other hand, shoot tips and stems with buds of grown-up grafting Guan Xi pemelo and Zhong Jiang pomelo were used for explants to study the main regulating and controlling factors in in vitro culture of vegetative organ of grating pomelo and measures of controlling micro-organism contamination. The final purpose was to establish a complete and efficient, applicable micropropogation technique system of pomelo.1. The results of studying micropropogation and regeneration system of pomelo seedling were as follows:(1) mature embryo cultured in dark condition for 7-14d could benefit elongation of plantlets.(2) Segments of epicotyls, hypocotyls and root tips could all directly form shoots, and the ability of shoot induction from epicotyls was much higher than that of hypocotyls and root tip segments. Epicotyl segments oriented with their apical ends protruding from the medium( t )produced more shoots than those when they were placed horizentally(-), with the highest shoot production freguency of 100%. Ability of direct shoot formation of sour pomelo was higher than Zhong Jiang pomelo when epicotyl was used for explants. (Rate of shoot formation was respectively 85.70% and 20.00%).(3) Subculture:6-BA was the first choice among CTKs and the suitable49concen- tration of 6-BA was under 2.00mg/L, and the effect of 6-BA combined with KT was better. The best medium was MS+IBA0.25mg/L+BA0.10 mg/L +KT0.40 mg/L +GA30.40 mg/L. Stems with bads used for explants formed shoots more easily than shoot tips used for explant. Sprouting rate of lateral bud was 96.67%-100%, 52.92%-73.32% respectively.(4) Root inducion of pomelo was very difficult .1/2 MSwas the suitable basal medium. Plantlets obtained in liquid culture transplanted on vegetable garden soil for 70d could reach a survival rate of 100%, extension growth of roots and plantlets being very remarkable and 100% of plantlets producing new roots.2. The results of studying micropropagation of vegetative organs of grafted pomelo were as follows:(1) Explants pre-cultured for 6hr by chemical bactericide: DuoJunLing, Rong JunLing, WanMeiLing and BaiJunQing 250 fold solution, surface contamination rate was reduced from 73.33% to 13.33%, Internal bacterium was controlled by Gentamicin 5-20M.U/L or Streptomycin 20-80M.u/L added in medium.Chemical bactericide combined with antibiotics could remarkably control contamination and stimulate bud sprouting. The effect of the treatment combinations of WanMeiLing(250 fold ,6h) +Gentamicin (20M.U/L) was the best.(2) Spring shoots of half lignification were the best explants in initial culturing.The best medium was MS+IBA0.25mg/L+BA0.50mg/L+KT0.25mg/L+ GA30.20mg/L+ AgNO34.00mg/L.(3) Subculture : The concentration of CTK was no more than l.00mg/L.The concentration range of IBA was 0.10-0.40mg/L. The most suitable medium for sprouting shoots was MS+IBA 0.25mg/L+ BA0.25mg/L+KT0.25mg/L+GA30.40mg/L; The most medium for stems was l/2MS+IBA0.20mg/L+BA1.00mg/L+GA30.10mg/L. (4) AgNO3 and STS (Silver thiosulfate) added in medium remarkably improved quality of sprouting shoots, restrained sprouting shoot from producing callus, helped the shoots grow normally. The most suitable concentration of AgNO3 was l0.00mg/L. the suitable concentration range of STS was 0.04-0.06m mol/L.