探讨云南山茶起源的一线曙光──野生二倍体类型在金沙江流域的发现

DAWN ON THE ORIGIN OF CAMELLIA RETICULATA──THE NEW DISCOVERY OF ITS WILD DIPLOID IN JINSHAJIANG VALLEY

新近发现的云南山茶（Ｃａｍｅｌｌｉａｒｅｔｉｃｕｌａｔａ）原始二倍体类型分布于金沙江坷谷流域的云南华坪县及四川盐边县，海拔１８００—２８００ｍ。其植被类型为亚热带常绿阔叶林与云南松的混交林，生境较为湿润。云南山茶原始二倍体类型的形态特征与广布的六倍体类群非常相似，而与怒江山茶及西南山茶的形态特征不同。二倍体的花粉母细胞在减数分裂中期Ｉ形成１５个二价体，间期的细胞核结构为球形前染色体型，分裂前期染色体为中间型，其核型公式为２ｎ＝３０＝２２ｍ＋２ｍ（ＳＡＴ）＋４ｓｍ＋２ｓｔ。根据本文和前人的研究结果，作者对云南山茶的形成和演化进行了讨论，否定了云南腾冲是云南山茶的原产地的观点，并认为二倍体类型的云南山茶与怒江山茶（Ｃ．ｓａｌｕｅｎｅｎｓｉｓ），西南山茶（Ｃ．ｐｉｔａｒｄｉｉｖａｒ．ｐｉｔａｒｄｉｉ）经过多次杂交和连续多倍化形成一个多倍体复合体，云南山茶的二倍体类型与怒江山茶及西南山茶可能是六倍体云南山茶的共有祖先。

The newly discovered diploid type of C. reticuIata was distributed in Jinshajiang valley with an elevation of 1651-2800 m, which is situated in Huaping of Yunnan province and Yanbi an of Sichuan provinee,This diploid occured in the habi tat with higher humidity. Its vege.tation was mainly consisted of evergreen broad-leaved forest and Pinus yunnanensis forest.The morphologic characters of this diploid type were very similar to those of its hexaploids.Its chromosomes in pollen mother cells formed 15 bivalents at metaphase I. The resting nuclei in somatic cell s were of the round prochromosome type,the somatic chromosomes at mitotic prophase were of the interstitial type .The karyotype at somatic metaDhase was ofrmulated as:2n=30=22m+2m(SAT)+4sm+2st.The discovery of diploid types ofC. reticulata negates the hy-pothesis that Tengchong county of Yunnan province is the original place of C. reticulata. Based on the results reported in this paper and by the previous authors,it was considered as follows: 1)C.reticulata forms a polyploid complex with its closely related diploid species C. saluenensis and C.pitardii var .pitardii ,2) the hexaploid C. reticulata was possibly resulted from interspecific hybridlzation and continued polyploidlzation among its ancient diploid species,3) the newly dis-covered dilpoid of C.reticulala and the above two diploid species were probably the foundation of this polyploid complex.