| Intergeneric hybridizations between the cultivated Brassicas species and Orychophragmus violaceus (L.) O. E. Schulz (2n=24) have been shown to be an efficient approach to produce Brassica aneuploids (including alien substitution and addition lines, hypoploids with partial Brassica complements). In this study, various B. juncea-O. violaceus substitution and addition plants with different numbers of O. violaceus chromosomes were identified and analyzed cytogenetically among the progenies of intergeneric hybrids covering these two species. These plants with novel chromosomal complements should provide the new materials for the genetic research and breeding of Brassica crops and the genomic relationships between the two genera. The main results were as follows.1. Morphology and cytogenetics of additional plantsWhile they were morphologically similar to B. juncea plants, the additional plants had larger and greener young leaves than those of mother B. juncea plants and the plant size was also generally larger. The additional plants usually showed the character of the basal clustering stems, which was characteristic of the O. violaceus plants. The plant with brown seeds (similar to those of O. violaceus), yellow-brown seeds and yellow seeds (similar to those of B. juncea) were found. All these plants were mixoploids (2n=30-41) with the highest chromosome number ranging from 37 to 41 in the ovary cell. With the succession of generations, highest chromosome numbers dropped, which was probably caused by the loss of alien O. violaceus chromosome during mitotic and meiotic divisions. These mixoploids also produced the mixoploidy progenies. Although various pairing configurations at diakinesis and segregation patterns at anaphase I (AI))were observed in pollen mother cells (PMCs) of each plants, and the lagging chromosomes/chromatids also frequently appeared in PMCs at AI/Telophase I (TI) and A II /T II, the pollen stainability was very high and the seed set was nearly normal. This showed that these additional plants could be easily propagated and preserved.2. Morphology and cytogenetics of substitution plantsThe substitution plants mainly kept the morphology of the mother plants of B. juncea, while having some O. violaceus characters, such as the basal clustering stems, the purple color on stems, the longer period of growth and the susceptibility to Sclerotinia sclerotiorum, some plants showed the character of appressed pods on inflorescences, which was not observed in two parents. All these plants were mixopliods (2n=30-36), butmajority of PMCs had 36 chromosomes, which were dominantly paired as 18 bivalents and segregated equally at AI. Some PMCs showed the different chromosomal pairings and segregations. In diakinesis PMCs, 1-2 labeled O. violaceus bivalents were identified and 1-2 O. violaceus chromosomes in each AI polar group, by applying genomic in situ hybridization method. The meiotic behavior of these plants contributed to their high fertility and the plant types in their selfed progenies.Different degrees of fatty acid modifications compared with B. juncea were shown by the substitution plants analyzed, the content of erucic acid decreased greatly (to 7.68%) and correspondingly the content of oleic acid increased.3. Somatic chromosome numbers at two growth stagesDifferent chromosome numbers were recorded in root-tip cells of seeds from hybrid progeny. But the percentage of cells (2n=36) was lower than that of the ovary cells from the same plants. This hinted that the loss of the O. violaceus chromosomes might occur during the process of embryo development or seed germination, and the cells with 36 chromosomes were more competitive during the plant growth.4. Cytogenetics of hypoploids plants (2n<36)The hypoploids plants (2n<36) with the same morphology as B. juncea plants grew normally and showed high fertility. Their chromosomes were mainly paired at diakinesis as 17II, 17II+II, minorly as 16II and segregated at AI as 17:17, 17:18 and 16:17, rarely as 16:19. PMCs with lagging chromosomes wer...
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