Study on somaclonal variation and utilization for plant breeding

莲花是一种广泛栽培、远缘繁殖的豆科牧草。71株植株，其中大部分是四倍体，是由来自单个原生质体的愈伤组织再生的。对它们的形态和农艺性状进行了评价，并与制种群体进行了比较。原生质体衍生(原克隆)群体的大多数性状的方差都小于种子产生群体的变异。原克隆群体所有性状的平均值显著向低值移动。然而，也观察到了新的表型变异，其值高于最初用于原生质体分离的植物的表型变异。在原生克隆中获得了比初始植株含有较少氢氰酸(对牛有毒性影响)的植株。总的来说，原生无性系的花粉育性显著低于种子产生的植株。这似乎部分归因于嗜铬细胞…异常的发生。在原生质体和/或愈伤组织培养过程中形成更多的基因组结构，这表明再生植株在中期I和后期I和II形成了单价体、滞后染色体和片段性染色体和桥。两种植物种子和5种原生克隆植物的线粒体DNA经Southern blotting分析。在13%的限制性内切酶和mtDNA探针组合中，种子植物表现出不同的杂交片段模式。另一方面，原克隆植株的大部分片段图谱与种子衍生植株的片段图谱相同。在所有限制性内切酶和探针的组合中，只有2个(4%)出现了片段变异，但所有变异的片段都与其中一种种子植物的片段相同。利用Rubisco小亚基、苯丙氨酸解氨酶和核糖体RNA等基因探针对细胞核DNA进行了分析。从实验中发现，这些基因非常稳定，没有任何变异。较少

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