The Study On Chromosome Squashing Technique Optimization And Karyotype Analysis Of Yam (Dioscorea Spp.)

In this experiment, root tips from the field plants and tissue culture seedlings as material, the chromosomal technique suitable for karyotype analysis was explored. In this paper, the chromosome number and karyotype was analyzed by the method of enzymatic hydrolysis and low osmotic. Henan Tiegun Yam (D. opposita Thunb.) is one of a popular cultivated variety of Chinese Yam in China with its economic value as a food plant and pharmaceutical functions. The karyotype of this well-known variety was reported for the first time. To lay a cytology foundation for the research and development of the germplasm innovation and utilization, genetic relationship, breeding engineering etc.. The main research results were as follows:1. The best way to obtain root tips was from cultivating yam tubers or bulbil in the lab room. With its easy operation, a much higher metaphase cells in each root. This method obtained more metaphase of which chromosomes were separated well.2. About pretreatment conditions,8-hydroxyquinoline or the mixture of8-hydroxyquinoline and colchicine as the pretreatment liquid was suitable for chromosome karyotype analysis.The best method of pretreatment was the root tips in2mmol/L8-hydroxyquinoline liquid for2h at the temperate of4℃.3. About the dissociation, the method enzymatic and acid was better than the method of acid. The former method showed the ideal disintegrate effect with the chromosomes clear. The best method for karyotype analysis was enzymatic and acid.4、In this paper, the chromosome numbers of two Chinese Yam (D. opposita Thunb.) and two Water Yam (D. alata L.) was investigated. The chromosome numbers of Henan Tiegun Yam HNTGH39and LYZ60are2n=120. The chromosome numbers of two Water Yam accessions DS31and HN42are2n=40. The Chinese Yam variety has more than one chromosome number, and the chromosome number2n=120was reported for the first time.5. Henan Tiegun Yam (D. opposita Thunb.) is one of a popular cultivated variety of Chinese Yam in China with its economic value as a food plant and pharmaceutical functions. The results indicated that the chromosome number was2n=120and karyotype formula was2n=120=96m (6SAT)+18sm (4SAT)+4st+2T, which belonged to "2B" type and whose evolution was relatively original. The absolute length was from0.688μm to2.628p.m and the relative length was from0.869%to3.319%, which was classified to micro type and small type. The coefficient of asymmetric was58.13%;The ratio of longest chromosome to the shortest was3.819and the proportion of exceed2:1was11.76%.