Analysis Of Genetic Diversity Among Sweetpotato Landraces In China

This paper describes, for the first time, the analysis of genetic diversity among sweetpotato landraces in China as revealed by morphological traits and molecular markers (RAPD, ISSR and AFLP). The sweetpotato accessions used in this study included 100 landraces from 6 provinces, Guangdong, Fujian, Zhejiang, Guangxi, Sichuan and Hubei in China and 8 breeding lines. The main results obtained are as follows:1. One hundred and four sweetpotato accessions were distinguished clearly based on 9 morphological traits, plant type, pubescence on vine, plant branch, dry weight, leaf shape, leaf color, root skin color, root fresh color and root shape, suggesting that Chinese sweetpotato landraces possessed sufficient genetic variation. Of these landraces, the landraces from Fujian had the highest level of variation. Chinese sweetpotato landraces had higher level of genetic diversity than the breeding lines. The dendrogram of the breeding lines based on morphological traits was not in agreement with known origin.2. Both 30 RAPD and 14 ISSR primers and 9 AFLP primer combinations were used for assessing genetic diversity among 108 sweetpotato accessions, and generated 218, 239 and 24S polymorphic bands, respectively. AFLPs were better than RAPDs and ISSRs in terms of the number of polymorphic bands and me experimental stability.3. The dendrogram of the breeding lines based on ISSRs agreed better with known origin man those based on RAPDs and AFLPs, suggesting that ISSRs are powerful markers for identifying accessions with known origin. The dendrogram based on the combined RAPDs, ISSRs and AFLPs dataset appeared to be appropriate in resolving relationships of the sweetpotato accessions. By using this approach, 108 sweetpotato accessions could be divided into four groups, and 6 of 8 breeding lines with known origin were clustered together.4. The genetic distances between landraces revealed by RAPDs, ISSRs and AFLPs differed greatly, being 0.0537-0.9418, 0.1678-1.4800 and 0.0227-0.9676, respectively, with the mean genetic distances of 0.3594, 0.5725 and 0.4754, respectively. These results supported the viewpoint that China is a secondary diversity center of sweetpotato.5. Based on the 3 molecular markers, landraces from Guangdong had the highest level of genetic variation in 6 provinces. Meanwhile, the genetic distances between Guangdong and the other 5 provinces were larger than those between the other 5 provinces. These results provided the support that sweetpotato was firstly introduced to Guangdong in china, from which sweetpotato was dispersed to other regions of China.6. The mean genetic distance between the Chinese sweetpotato landraces and the breeding lines calculated by the combined RAPDs, ISSRs and AFLPs dataset was 0.5269. Moreover, the landraces from Guangdong were most distantly related to the breeding lines in 6 provinces. Thus, the utilization and protection of the landraces from Guangdong should be emphasized in sweetpotato breeding.