| Garlic (Allium sativum L.) is a worldwide vegetable and had been cultivated since ancient times. Due to its sexual sterility, garlic is propagated vegetatively through cloves or bulbs. Two main problems associated with the vegetative propagation of garlic are (1) perpetuation and wide spread of viral infection and (2) low propagation rate.Shoot-tip culture is proved to be an effective method for producing virus-free garlic seedlings. However, because of low micropropagation rate, virus-free plantlets are still very expensive which limits their practical use.This study focuses on direct shoot regeneration from garlic root tips and shoot proliferation for speeding up multipropagation of virus-free garlic.1. Induction of the adventitious buds from root tips in garlicUsing MS as basic medium, the effect of different varieties, rooting time, root-tip length and culture condition (temperature, photoperiod, basic media, sugar sources and concentration, pH value and different hormone concentration and combinations) on direct adventitious shoot formation from garlic root tips was studied. The results showed that 2~3mm root tips from the cloves rooting for 4-8 days have a high frequency bud initiation. The induction rate and the number of adventitious buds varied with varieties. Root tips from different rooted shoots induced from different explants all can directly regenerate adventitious buds and virus-free garlic can be cycly multiplicated through root-tip culture. The differentiation rate of buds of root tips inducted from plantlets from stem tips and root tips and adventitious shoot number was low than that from garlic cloves. Root tips had no bud regeneration when they were cultured at 15C or 20 C and the induction rate and the number of buds increased with the rise of temperature when they were cultured above 28 C. Continuous light had a positive effect on adventitious bud formation and number. The optimal medium for root tip culture was MS salt+B5 organic medium or MS containing sucrose 20~50g/L, BA 2.0~5.0mg/L, NAA1.0mg/L,at pH5.8~6.2.2. Subculture of adventitious buds from root tips in garlicThe growth and proliferation of adventitious buds from different initiation media were investigated. The results indicted that there were more shoots per explant on the initiation medium containing lOmg/LBA, Img/LNAA and adventitious buds from the initiation medium containing 2.0mg/LBA, 0.Img/LNAA grow vigorously. The optimal medium for adventitious bud growth was MS salt+B, organic (or 65) +1.0mg/LBA+0.05mg/LNAA and The optimal medium for adventitious bud proliferation was and MS salt+Bs organic (or 85) +0.5mg/LBA.3. Bulblet formation and swelling of Garlic in vitro and performance in field85 as basic medium, the study on effect of sucrose concentration ,ethephon and PPsss on bulblet induction and swelling of Garlic in vitro demonstrated that bulblet formation andswelling were significantly enhanced by increasing sucrose to 90g/L, Ethephon and had positive effects on bulblet fomation and swelling, on the 85 medium supplemented with sucrose 90g/L, PP333 1.0mg/L, bulblet swelled best, fresh weight can reach 312mg, and on the medium containing 90g/L sucrose and 2.0mg/LPPs33, 33.1% bulblets tillered. Bulblet fresh weight was related with seedlings germination, growth, and bulb formation. Bulblet above 300mg had higher germination rate, seedlings grew strong and produced heavier bulb. Bulblets were transplanted into pots, and zero generation grew normally, but plants were short and produced small bulbs with few clovs. First generation grew normally, and plant leaf number, height, leaf width significantly increased compared with zero generation. Ffirst generation can form much heavier bulb than zero generation with more clovs, but still lighter compared with control. It is possible that second generation has no difference with control or surpass control. |
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