Abstract: Deqin wild alfalfa(Medicago sativa L.)was found in Deqin County of Diqing Tibetan Autonomous Prefecture in Yunnan Province.The wild alfalfa populations distribute mainly in xerothermic valleys or the verge of forests at the altitude of 2000-3000 m in drainage area of Lancang River and the Jinsha River.Being a component of shrubbery layer of Sophora viciifolia Hance,they can flourish in farmland areas.Investigation show that rainfall was the most influential ecological factor for their distribution.They grew normally in locations close to water sources in xerothermic valleys.They grew poor in natural communities;if other species dominated,their phenophase would be retarded.They showed an abundaot root system which could be beneficial for soil and water conservation.They gave a tremendous growth density as more than 800 ramifications/m² with ample water supply and favorable management;they produced more than 5 kg/m² in natural condition.Karyotype analysis indicated that Deqin alfalfa is tetraploid,2n=32.The investigation of their origin showed: the first,it must had been dispersed to Tibet from Qinghai Province and Gansu Province in ancient times,then survived in southern canyon of transect mountains where fine living conditions offered; then gradually passed down along rivers’ downstream reaches;the second,alfalfa’s distribution in Deqin areas might had some relations with Buddhism(Buddhism prevalent in Tibet) dissemination. Deqin wild alfalfa populations are the unique alfalfa germplasm distributing as communities found in Yunnan Province.With the diversity of geographical distribution and morphological characteristics it may contain rich genetic foundations, especially ones growing normally in xerothermic valleys may contain unique germlasm.

Key words: Wild alfalfa, Population characteristics, Origin

摘要： 德钦地区野生紫花苜蓿(Medicago sativa L.)发现于云南省迪庆藏族自治州德钦县,主要分布于澜沧江、金沙江流域海拔2000~3000 m的干热河谷和森林边缘,是白刺花(Sophora viciifolia Hance)灌丛的草本成分之一,并在农区大量生长,调查表明,野生紫花苜蓿的生长和分布明显受降水量的影响;在干热河谷地区正常生长,但不能离水源太远;在自然群落中的竞争力较弱,当群落另有优势种时其物候期明显推迟;其根系发达,具有很强的水土保持能力;在水分及管理较好的条件下分枝可达800/m²以上;在自然状态下产草量达5 kg/m²以上;染色体为2n=32,系四倍体。考证分析结果初步认为:德钦地区野生紫花苜蓿来源由我国青海和甘肃传入西藏,然后在横断山脉南部峡谷地区生存下来,并沿河流方向逐渐向下游传播;在德钦地区的扩展可能与藏传佛教的传播活动有关。德钦地区野生紫花苜蓿是云南发现的唯一成群落分布的苜蓿资源,其多样的形态和地理分布特征,孕育着丰富的遗传基础,特别是在干热地区生存可能孕育特异性种质。

关键词: 野生苜蓿, 群落特征, 来源