Department of Botany, The Field Museum of Natural History, 1400 S. Lake Shore Drive, Chicago, Illinois 60605-2496 USA;
Am J Bot. 2002 Jul;89(7):1042-56. doi: 10.3732/ajb.89.7.1042.
In continuing study of the origins of the octoploid tuber crop oca, Oxalis tuberosa Molina, we used phylogenetic analysis of DNA sequences of the chloroplast-active (nuclear encoded) isozyme of glutamine synthetase (ncpGS) from cultivated oca, its allies in the "Oxalis tuberosa alliance," and other Andean Oxalis. Multiple ncpGS sequences found within individuals of both the cultigen and a yet unnamed wild tuber-bearing taxon of Bolivia were separated by molecular cloning, but some cloned sequences appeared to be artifacts of polymerase chain reaction (PCR) recombination and/or Taq error. Nonetheless, three classes of nonrecombinant sequences each joined a different part of the O. tuberosa alliance clade on the ncpGS gene tree. Octoploid oca shares two sequence classes with the Bolivian tuber-bearing taxon (of unknown ploidy level). Fixed heterozygosity of these two sequence classes in all ocas sampled suggests that they represent homeologous loci and that oca is allopolyploid. A third sequence class, found in eight of nine oca plants sampled, might represent a third homeologous locus, suggesting that oca may be autoallopolyploid, and is shared with another wild tuber-bearing species, tetraploid O. picchensis of southern Peru. Thus, ncpGS data identify these two taxa as the best candidates as progenitors of cultivated oca.
在继续研究八倍体块茎作物秘鲁玛卡（Oxalis tuberosa Molina）的起源时，我们利用叶绿体活性（核编码）谷氨酰胺合成酶（ncpGS）的 DNA 序列的系统发育分析，从栽培的秘鲁玛卡、其在“Oxalis tuberosa 联盟”中的亲缘种以及其他安第斯 Oxalis 中获得。在栽培种和玻利维亚一个尚未命名的野生块茎种个体中发现的多个 ncpGS 序列通过分子克隆进行了分离，但一些克隆序列似乎是聚合酶链反应（PCR）重组和/或 Taq 错误的产物。尽管如此，三类非重组序列中的每一类都与 O. tuberosa 联盟的一个不同部分在 ncpGS 基因树上相连。八倍体秘鲁玛卡与玻利维亚的一个具有块茎的种（未知的倍性水平）共享两个序列类。所有被采样的秘鲁玛卡中这两个序列类的固定杂合性表明它们代表同源基因座，并且秘鲁玛卡是异源多倍体。在 9 个秘鲁玛卡植物样本中发现的第三个序列类可能代表第三个同源基因座，表明秘鲁玛卡可能是自交异源多倍体，并且与另一个具有野生块茎的物种，秘鲁南部的四倍体 O. picchensis 共享。因此，ncpGS 数据将这两个种鉴定为栽培秘鲁玛卡的最佳候选祖先。
