Research On In Vitro Culture Of Dioscorea Rotundata And Its Buds Cytohistology

Dioscorea rotundata, the’white yam’of’Guinea yam’, is a species of Dioscoreaceae native to Africa. The yam is not only a high energy food, but a king crop of the people in West Africa. There are not only starch, proteins, but also tannin and sapogenins present in the tuberous root, which are known to have high efficacy in medical applications. Researches on in vitro plantlet and tuber formation has been reported in other countries, however its little known in our country. In this paper, the tuberous root of Dioscorea rotundata was used as the material, we conducted some research on the culture in vitro and cytohistological observation of bud regenerated. The results will lay ground work for rapid propagation of Dioscorea rotundata in China. The main results are as follows:1. A in vitro protocol was developed for multiplication of Dioscorea rotundata by using leaves, stem and tuberous root derived from plants grown in pot as explants. The optimum callus induction medium is MS+2,4-D4mg/L+6-BA1mg/L,4mg/L6-BA added to the medium is better for Buds regeneration. Tuberous root is browning seriously in culture and the callus inducing rate is0, whereas the node with axillary bud is suitable for callus induction.2. The optimum medium for proliferation of axillary bud on the shoot is: MS+BA3.0mg/L+NAA0.2mg/L,(3.1shoots per explant).3. Increasing of6-BA and agar concentration or adding of0.3%active coal could decrease browning in the culture system.4.There are two bud regeneration pathways during the in vitro culture of Dioscorea rotundata:organogenesis and direct regeneration. The cytohistological observation showed that:Parenchyma cells of both two explants experience the induction phase, division phase and then develop towards embryonic cell. The cells cultured in the medium added with2,4-D develop into callus formation phase directly, in which suffered dedifferentiation and redifferentiation, as a result, knowing the essence and change of callus is the key to callus utilization. On the other hand, the cells cultured in the medium added with6-BA start up and divide into embryonic mass that will develop into bud primordium,5. Plantlets transplant survival rate is closed connected with culture medium and acclimatization.