| Taro[Colocasia esculenta(L.) Schott],belonging to Colocasia of Araceae,is a perennial or annual training herb. It is one of the major starchy food plants in many countries and ranked 14th in consumption amount among the major vegetables in the world in 1997. Because taro is a kind of vegetatively propagated crop, few extensive studies on taro have been conducted, especially in genetic resources and phylogeny. On the other hand, taro classification is mainly based on flower characters such as female and male inflorescence, and size and character of neutral flower and its accessories, and it seldom flowers, so it is very difficult to classify taro. At present, the most taro classification characters are morphological. Taro classification is different, and sources of some accessions and theirs relation are unclear. As a result, it is not useful for the research of taro resources and variety breeding. In consequence, it is essential to conduct researches on genetic diversity and classification of taro at the DNA level using modern biological technique. Here, genetic diversity of 47 taro materials and 2 genus Alocasia (Schott) GDon materials had been conducted using RAPD, and the main results as follows:1.Three methods-CTAB method, SDS method, and high salinity and low pH method were used to extract genomic DNA from leaves of taro. The DNA samples of the three methods were tested by spectrophotometer, agarose gel electrophoresis and RAPD. The result was that all of the three methods could be used for extracting genomic DNA from leaves of taro, and that the CTAB method was the best ones through which the production had the highest purity. So, we choose CTAB method to conduct following experiments.2. Some essential factors that might affect the result of RAPD assay were tested and compared. An optional reaction system suitable for the assay and usage of RAPD in taro was established. The volume of amplified reaction was 25ul,containing 10 X buffer (Mg2+, 20mmol/L) 2.5ul, genomic DNA (10ng/ul) 3ul, primer (4.625umol/L) 2ul, dNTP (10mmol/L) 0.5ul, Taq DNA ployrase (2U/ul) 0.5ul, andpure water 16.5ul. The reaction program was devised for 38 cycles, each with 94 C denaturation for 1min, 38C annealing for Imin, 72C extension for 2min, and 94C predenature for 3min in the former denature and 72C postextension for 5min in the final extension.3. In the paper , forty-seven accessions of Colocasia escidenta, and two accessions of genus Aloca.sia were evaluated for genetic diversity using random amplified polymorphic UNA (RAPD) markers. Twenty primers were chosen for they showed strong , reproducible amplification and distinct polymorphisms from 150 10-base arbitrary primers. A total of 150 DNA fragments were amplified from 300bp~2000bp, among which 127 were polymorphics, and which accounted for 84.7%. The average number DNA bands produced by each primer was 7.5. Those above results showed that the genetic diversity of 49 accessions was high.4.Through UPGMA cluster analysis of genetic linkage distance, the accessions were separated into 2 main groups with Colocasia esculenta divided into 6 sections, which were green, purple, mother, red-bud, petiole and inflorescence types of taro, respectively. It was found that the classification result through RAPD markers was accordant with that resulted from some botanic characters. It was clear from the morphology observation and RAPD analysis of taro that inflorescence types of taro such as Yunnan Hongyu and Hubei Gufuyu was closest to petiole taro in relationship than purple and green types of taro. This result suggested that the eating inflorescences taro such as Yunan Hongyu and Hubei Gufuyu could be classified as var. Inflorescens, which supported the opinions of Cai K H (1995) and Pu Y D (1999). They suggested that taro could be classified into three varieties, which are var. petiolatus Chang, var. cormosus Chang, and var. Inflorescens. |
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