Tu Yuqin, Sun Jian, Ge Xianhong, Li Zaiyun
National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding Technology, National Center of Oil Crop Improvement-Wuhan, Huazhong Agricultural University, Wuhan, P. R. China.
Ann Bot. 2009 May;103(7):1039-48. doi: 10.1093/aob/mcp045. Epub 2009 Mar 2.
Partial hybrids with female-parent-type phenotypes and chromosome numbers but altered genomic compositions have been reported in wide crosses of several plants. In order to introgress desirable genes from a wild relative, Isatis indigotica (a dye and medicinal plant; 2n = 14), into Brassica crops, intertribal sexual hybridizations were carried out with B. rapa (2n = 20), and the resulting hybrids and their progenies were characterized.
Using genomic in situ hybridization (GISH) and amplified fragment length polymorphism (AFLP), chromosomal/genomic components of the hybrids and their progenies were analysed.
Many hybrid plants were obtained from the mature seeds harvested from the B. rapa x I. indigotica cross, and these exhibited different morphological traits. However, the majority of them did not survive and only three plants grew to maturity. These three hybrids showed poor growth and much smaller stature than the two parents, but had some morphological traits and chemical composition of I. indigotica. One plant had 2n = 10, the haploid chromosome number of B. rapa, and was absolutely sterile. The other two plants had 20 and 22 somatic chromosomes and were male sterile but produced seeds following pollinations with B. rapa. All back-cross progenies over several generations maintained a B. rapa-type phenotype and also displayed some variations in morphological characters and fatty acid compositions. They were all 2n = 20 and showed good seed-set. The hybrid with 2n = 22 produced some progeny plants with 2n = 21 and 2n = 22. GISH detected two chromosomes of I. indigotica in the hybrid with 2n = 22 but none in the one with 2n = 20. AFLP bands specific for I. indigotica, novel for two parents or absent in B. rapa, were detected in the two hybrids and their progenies. These progeny plants were novel B. rapa types with an altered genomic constitution or alien additions.
Complete or partial chromosome elimination and diploidization with genomic rearrangements were considered to lead to the formation of partial hybrids in this cross.
在几种植物的远缘杂交中，已报道出现了具有母本类型表型和染色体数目但基因组组成改变的部分杂种。为了将野生近缘种菘蓝（一种染料和药用植物；2n = 14）的优良基因导入芸苔属作物，开展了与白菜型油菜（2n = 20）的族间有性杂交，并对所得杂种及其后代进行了特征分析。
利用基因组原位杂交（GISH）和扩增片段长度多态性（AFLP）分析杂种及其后代的染色体/基因组组成。
从白菜型油菜×菘蓝杂交收获的成熟种子中获得了许多杂种植物，这些杂种表现出不同的形态特征。然而，它们中的大多数没有存活下来，只有三株生长到成熟。这三个杂种生长不良，株高比两个亲本小得多，但具有菘蓝的一些形态特征和化学成分。一株植物的染色体数为2n = 10，即白菜型油菜的单倍体染色体数，完全不育。另外两株植物的体细胞染色体数分别为20和22，雄性不育，但用白菜型油菜授粉后能产生种子。经过几代的所有回交后代都保持了白菜型油菜的表型，并且在形态特征和脂肪酸组成上也表现出一些变异。它们的染色体数均为2n = 20，结实良好。染色体数为2n = 22的杂种产生了一些染色体数为2n = 21和2n = 22的后代植株。GISH在染色体数为2n = 22的杂种中检测到两条菘蓝染色体，而在染色体数为2n = 20的杂种中未检测到。在这两个杂种及其后代中检测到了菘蓝特有的AFLP条带，这些条带对两个亲本来说是新的，或者在白菜型油菜中不存在。这些后代植株是基因组组成改变或有外源附加的新型白菜型油菜。
在该杂交中，完整或部分染色体消除以及伴随基因组重排的二倍体化被认为导致了部分杂种的形成。
