文心兰黄化突变体的初步研究

The Preliminary Study of Xantha Mutants in Oncidium

对文心兰品种百万金币的10份体细胞无性系黄化突变体的叶绿素合成和叶绿体结构进行初步分析。结果表明：（1）黄绿条纹突变体（Y1～Y6）的总叶绿素（Chl）和类胡萝卜素（Car）含量显著降低，分别为正常植株的28．47％～87．21％和35．82％～91．98％；Y2、Y3、Y5和Y6的叶绿素a／b比值（Chla／b）显著升高，Y4的Chla／b显著降低；叶绿素合成分别在粪卟啉原Ⅲ（CoprogenⅢ）到原卟啉Ⅸ（ProtoIX）（Y1、Y2、Y3、Y5和Y6），及ProtoIX到镁原卟啉Ⅸ（Mg-ProtoⅨ）（Y4）的位点受阻。（2）完全黄化突变体（Y7～Y10）的Chl和Car含量显著降低，分别为正常植株的10．94％～15．22％和22．06％～28．94％；Chla／b显著升高，Chl／Car显著降低；叶绿素合成在CoprogenⅢ到ProtoⅨ的位点受阻。（3）黄叶组织内叶绿体和基粒片层减少；部分叶绿体异常，基粒片层稀疏松散或缺失，基质中含较多嗜饿颗粒和囊泡。（4）利用ISSR引物UBC827和UBC897在突变体中各检测出1个多态性位点。叶绿素合成受阻和叶绿体发育异常导致叶绿素含量减少是突变体叶片呈现黄色的主要原因。

The chlorophyll synthesis and chloroplast uhrastrueture were investigated in 10 xantha mutants of Oncidium cuhivar ＇ Milliongolds＇. The results showed that ： （ 1 ） The chlorophyll （Chl） and carotene （Car） contents of mutants with yellow streak leaves（ Y1 - Y6） reduced significantly and accounted 28.47% - 87.21% and 35.82% - 91.98% of that of normal plant respectively. The ratio of chlorophyll a and chlorophyll b（ Chl a/b）increased significantly in Y2,Y3, Y5 and Y6, but decreased significantly in Y4. The chlorophyll synthesis was blocked at the reactions from coproporphyrinogen Ⅲ （ Coprogen Ⅲ ） to protoporphyrin IX （ Proto IX ） （ Y1, Y2, Y3, Y5 and Y6 ） , and from Proto IX to Mg - protoporphyrin IX （ Mg - Proto IX ） （ Y4 ） respectively. （ 2 ） The Chl and Car contents of mutants with whole yellow leaves（Y7 -Y10）reduced significantly and accounted 10.94% - 15.22% and 22.06% - 28.94% of that of normal plant respectively. Significant higher Chl a/b and lower Chl/Car were observed in Y7 - Y10. The chlorophyll synthesis was blocked at the reaction from Coprogen Ⅲ to Proto IX. （3）Less chloroplasts and grana lamellas were observed in the yellow leaves of xantha mutants. Some chloroplasts exhibited malformed morphology with sparse and loose grana lamells, and with more osmioplilic granules and vesicas. （4）Two polymorphic loci were detected among the xantha mutants using ISSR primer UBC827 and UBC897. It was concluded that yellow leaves of mutants resulted from the decrease of chlorophyll, which caused by the blocking of chlorophyll synthesis and the malformation of chloroplast.