Study on somaclonal variation and utilization for plant breeding

莲藕是一种广泛种植的近交豆科饲料作物。71株；其中大部分为四倍体，由单一原生质体形成的愈伤组织再生而来。对其形态和农艺性状进行了评价，并与实产群体进行了比较。原生质体衍生（原克隆）群体中大部分性状的方差小于种子产生群体。原无性系群体各性状的平均值明显向低值偏移。然而，也观察到新的表型变异，其值高于最初用于原生质体分离的植物。在原克隆中获得的植物比最初的植物含有更少的氢氰酸（对牛有毒性作用）。一般来说，原无性系的花粉育性明显低于种子产生植株。在原生质体和/或愈伤组织培养过程中，有更多的结构，如在再生体的中期、后期和II期形成的一价染色体、滞后染色体和片段染色体和桥。然而，铬的某些结构的变化没有引起任何畸形的形态。采用Southern blotting对2个植物衍生种子和5个原克隆植物的mtDNA进行了分析。在所有限制性内切酶和mtDNA探针的组合中，13%的种子源植物显示出不同的杂交片段模式。另一方面，原无性系植物的大部分片段模式与种子衍生植物的片段模式相同。在所有限制性内切酶和探针的组合中，只有2个（4%）显示片段变异。然而，所有不同的片段都与一种种子源植物的片段相同。这一事实表明，变异可能经常发生在线粒体基因组的同一位置，或者变异可能在恒定的方向上发生。采用Rubisco小亚基基因、苯丙氨酸解氨酶基因和核糖体RNA探针对核dna进行分析。从这个实验中，我们发现这些基因非常稳定，没有任何变异。少

Lotus corniculatus L. is a widely cultivated, outbreeding, leguminous forage crop. Seventy-one plants ; most of which were tetraploid, were regenerated from calli derived from a single protoplast. Their morphological and agronomic traits were evaluated and compared with those of the seed-produced population. The variances of most of the traits in the protoplast-derived(protoclonal)population were smaller than those of the seed-produced population. Mean values of all the traits of the protoclonal population shifted significantly towards lower values. However, new phenotypic variants with higher values than those of the plant initially used for protoplast isolation were also observed. Plants with less hydrocyanic acid(which has a toxic effect on cattle)than the initial plant were obtained in the protoclones. Generally, the pollen fertility of protoclones was significantly low compared with the seed-produced plants. This seems to be partly due to the occurrence of abnormalities in chromos … More ome structure during protoplast and/or callus culture, as suggested by the formation of univalents, lagging, and fragment chromosomes and bridges at metaphase I and anaphase I and II of the regenerants. The changes in chrome some structure, however, did not induce any malformed morphologies.The mtDNA of two plants derived seeds and five protoclonal plants were analyzed by Southern blotting. Seed-derived plants showed different hybridized fragment patterns in 13% of all the combinations of restriction enzymes and mtDNA probes. On the other hand, most of the fragment patterns of protoclonal plants were the same as those of one of plants derived from the seeds. Only 2(4%)of all the combinations of restriction enzymes and probes showed fragment variations.However, all of the varied fragments were identical to the fragments of one of the seed-derived plants. This fact indicates that variations may occur frequently at the same location of the mitocondrial genome or else the variations may occur in constant directions.The nuclear DNAs were also analyzed by using the probes of genes of small subunit of Rubisco, phenylalanine ammonia lyase and ribosomal RNA. From this experiment, it was found that these genes were very stable without any variations. Less