嫁接导致的绿豆可遗传性变异及其在绿豆育种中的应用

植物嫁接可以导致接穗的后代中有可遗传性变异的发生。我们将绿豆 (Vignaradiata (L .)Wilczek)的幼苗嫁接在红薯 (Ipomoeabatatas (L .)Lam .)的茎上 ,维护其生长至结实。将收获的绿豆种子连续几代播种于普通环境时 ,其后代中出现了明显的遗传变异。这些变异在未经嫁接的绿豆接穗品系中并不出现。为了研究这种嫁接诱导变异现象可能的机理 ,我们对变异品系的细胞质和细胞核DNA进行了分析。结果显示 ,在原绿豆和变异品系之间未发现细胞质DNA的RFLP(限制性酶切片段多态性 )差异。而细胞核DNA却发生了高频率的序列重组。同时 ,本研究没有发现砧木与接穗间基因转移的迹象。根据以上事实 ,我们推测远缘嫁接变异很有可能是嫁接生长逆境诱导的抗逆变异。

Graft-induced Inheritable Variation in Mungbean and Its Application in Mungbean Breeding

Graft can induce inheritable variations in the progenies of the scion plants. Seedling of mungbean ( Vigna radiata (L.) Wilczek) was grafted onto the stem of sweet potato ( Ipomoea batatas (L.) Lam.). The growth of the scion was maintained until the scion produced selfed seeds. We sowed the seeds for several generations under normal conditions. Distinct genetic variations appeared in the progenies. Similar variations did not appear in the generations of the scion sowed normally without graft. The variations seemed to be induced by the graft and they inherited steadily. For understanding the possible mechanism of the phenomenon (graft_induced inheritable variation), we analyzed the cytoplasmic and genomic DNA of the variations. The results showed that there was no restriction fragment length polymorphism (RFLP) in the cytoplasmic DNA between the original scion and the variation. However, significant difference between the scion and variation was recognized by random amplified polymorphic DNA (RAPD) analysis. In addition, there was no evidence that indicated the gene transformation from stock to scion. Our results suggest that the non_specific grafting has a pragmatic potential for plant breeding and crop improvement and, the genetic variation seems not to be caused simply by DNA transformation but most likely the stress induced mutation.