|其他摘要||Hulless barley (Hordeum vulgare L. var. nudum Hook. f.) belongs to the genus Hordeum in the Poaceae (grass family). Hulless barley is distributed widely, but its frequency greatly differs among regions. In China, hulless barley is distributed in the Qinghai-Tibet Plateau, covering Tibet, Qinghai, Gansu, Sichuan and Yunnan provinces. In Yunnan Province, hulless barley is mainly distributed in Diqing Tibetan Autonomous Prefecture. Located in the southern part of the Qinghai-Tibet Plateau and the eastern Himalayas, Diqing is the junction of Yunnan, Tibet and Sichuan provinces. The wide geographic and climatic distribution is indicative of the fact that there exists a tremendous genetic diversity in hulless barley. In Diqing Prefecture, the majority is Tibetan (or Zang minority in Chinese) and traditional Tibetan practices play an important role, particularly in natural resource management and farming systems of hulless barley.
The genetic diversity of different original hulless barley had been described by various authors. Most researches have focused on hulless barley in the Himalayan region. However, little is known about the detailed information on genetic diversity of Diqing hulless barley landraces. In the present study, we applied approaches of participatory rural appraisal (PRA), ethnobotany, questionnaires and semi-structured interview for data collection related to Traditional Tibetan culture and knowledge on hulless barley; analyzed the morphological diversity of hulless barley landrace from Diqing Prefecture using morphological traits; and analyzed the genetic diversity of hulless barley using AFLP markers. The aims of this study are not only to analyze the genetic diversity of hulless barley from Diqing, but to validate the high genetic diversity level of hulless barley landraces in Diqing through the traditional conservation system. The main results are summarized as follows:
1. Benefiting from the special location with diverse ecogeography, climate and biodiversity conserved through traditional Tibetan culture, there are rich genetic germplasm resources of hulless barley in Diqing. Hulless barley is closely associated with Tibetan nature worship, religion, lifestyle, and diet. As a “key species”, hulless barley is a bridge to connect the biodiversity and culture.
2. It is a convenient method using morphological traits to analyze the genetic diversity. In the present study, we analyzed the morphological diversity of hulless barley landraces from Diqing using eleven morphological traits. The results of average, SSD and coefficient of variation (CV) showed that there are rich morphological variations in hulless barley landraces. Among these morphological traits, the CV of awn property, grain color and spike density reached more than 50%. It indicated that three morphological traits mentioned above are the important indexes to reflect the level of diversity. One of the main reasons of high level morphological variation of hulless barley may be due to environmental heterogeneity. The rich genetic diversity of hulless barley landraces In Diqing Prefecture at different altitudes can be explained by the species’ need to adapt to the differentiation of environmental conditions and other factors.
3. The present study demonstrated the potential of the AFLP technique for the generation of extensive genetic polymorphism data appropriate to the analysis of individual DNA profile, population structure and genetic diversity. Our study detected a higher rate of polymorphism and provided higher resolution due to generation of large number of loci. A total of 576 bands were generated, of which 517 (89.76%) were polymorphic.
4. The results of genetic diversity among hulless barley populations indicated that there were significant differences in genetic diversities among the 13 populations. The three populations representing Diqing Prefecture recorded the highest level of genetic diversity, and the highest percentage of polymorphic loci, expected heterozygoity and Shannon’s information index. Among three population from the prefecture, the genetiv diversity of Deqin population is the highest (He=0.0924, I=0.1614, PPB=59.72%). This may be due to the sustainable utilization and conservation through Tibetan traditional culture, and due to environmental heterogeneity as landraces in Diqing were collected from different altitudes ranging from 1751m to 3550m. In the comparing of genetic diversity between landraces and bred-accessions, the genetic diversity of landraces was quite high compared with bred-accessions. The low level of diversity in bred-accession may be attributed to uniformity of the environmental variables and the similar genetic background of breeding materials.
5. On average, AFLP analysis revealed that the genetic similarities were close between populations, ranging from 0.9356 to 0.9982. One of the major contributing factors to the high degree of genetic similarity observed in different populations of hulless barley may imply its evolutionary status as a self-pollinating angiosperm. The heterogeneity level of hulless barley is not as high as that of cross-pollinating plants because it is a self-pollinating plant. Gst and AMOVA analyses overall loci showed that the degree of diversity within population was greater than that among populations. The proportion of total allelic diversity found among populations was Gst = 0.2587. The mean Gst over all loci indicated that, on average, 25.87% of the variation was among populations and 74.13% (1– Gst) was within populations. The examination of hierarchical partitioning of genetic variation by AMOVA demonstrated that 3.32% was attributed to population differences while 96.68% of the total variation was attributed to individual differences within the population. These results are in contrast to expectations under conditions of limited migration between populations and the high selfing rate within population. However, these results are in agreement with other studies on barley where a higher degree of genetic diversity is partitioned within, rather than between populations. The genetic relationship among the 13 populations was displayed in a tree diagram using UPGMA and the results showed that the genetic distances of landrace populations with similar geographical origin were relative similarity.
6. Benefiting from the special location with environmental heterogeneity associated with traditional Tibetan culture, Diqing Prefecture forms an important reservoir of biodiversity, and there are rich germplasm resources of hulless barley in this region. To promote the conservation and sustainable use of hulless barley landraces in Diqing, in situ (on farm) and ex situ approaches should be considered. The two methods are mutual-complementary rather than antagonistic. Practically, this would involve farmer-training exercises to maintain good collection and management practices of currently hulless barley germplasm. Furthermore, a long term conservation strategy of hulless barley landrace should be commended, that is, ex situ conservation. The seeds of hulless barley landraces, under the different eco-geography and climate in the prefecture, should be collected and stored in the seed bank, and used these resources to propagate new seeds routinely. AFLP molecular marker can also provide the basis for handling and evaluating hulless barley germplasm resources and using it in breeding improvement. In conclusion, the Traditional Tibetan culture and management practices can contribute to the conservation strategies to protect the rich genetic diversity of hulless barley landraces.|