International Institute of Tropical Agriculture (IITA), Oyo Road, PMB 5320, Ibadan, Nigeria.
Theor Appl Genet. 1994 Nov;89(6):719-27. doi: 10.1007/BF00223711.
Chloroplast DNA (cp) and nuclear ribosomal DNA (rDNA) variation was investigated in 45 accessions of cultivated and wild Manihot species. Ten independent mutations, 8 point mutations and 2 length mutations were identified, using eight restriction enzymes and 12 heterologous cpDNA probes from mungbean. Restriction fragment length polymorphism analysis defined nine distinct chloroplast types, three of which were found among the cultivated accessions and six among the wild species. Cladistic analysis of the cpDNA data using parsimony yielded a hypothetical phylogeny of lineages among the cpDNAs of cassava and its wild relatives that is congruent with morphological evolutionary differentiation in the genus. The results of our survey of cpDNA, together with rDNA restriction site change at the intergenic spacer region and rDNA repeat unit length variation (using rDNA cloned fragments from taro as probe), suggest that cassava might have arisen from the domestication of wild tuberous accessions of some Manihot species, followed by intensive selection. M. esculenta subspp flabellifolia is probably a wild progenitor. Introgressive hybridization with wild forms and pressures to adapt to the widely varying climates and topography in which cassava is found might have enhanced the crop's present day variability.
对 45 份栽培和野生曼尼希特属植物的叶绿体 DNA(cp)和核核糖体 DNA(rDNA)变异进行了研究。利用来自绿豆的 8 种限制酶和 12 种异源 cpDNA 探针，鉴定出 10 种独立突变，包括 8 种点突变和 2 种长度突变。限制性片段长度多态性分析定义了 9 种不同的叶绿体类型，其中 3 种存在于栽培品种中，6 种存在于野生种中。利用简约法对 cpDNA 数据进行的系统发育分析产生了一个关于木薯及其野生亲缘种 cpDNA 谱系的假设系统发育，与该属的形态进化分化相一致。我们对 cpDNA 的调查结果，以及在基因间 spacer 区 rDNA 限制酶位点变化和 rDNA 重复单元长度变化（使用 taro 的 rDNA 克隆片段作为探针）的结果表明，木薯可能是由一些曼尼希特属植物的野生块茎品种驯化而来，然后经过了密集的选择。M. esculenta subspp flabellifolia 可能是一个野生祖先。与野生种的渐渗杂交以及适应木薯分布的广泛变化的气候和地形的压力，可能增强了该作物目前的变异性。
