| Cauliflower, one of the main vegetable crops, was deeply loved by consumers in our country. Due to market directed selection in the long breeding history, genetic background of cauliflower become narrowed, which resulted the difficulty in the progress of pathogen resistant breeding and yield and quality improvement. Interspecific hybridization combined with backcrossing can introduce the wild heterogenous germplasm into the cultivar and enrich the genetic diversity, which is one of the efficient ways to get an original germplasm innovation for breeding.In this work, population of the advanced selfed and/or backcrossed progenies of somatic hybrids of cauliflower and Brassica nigra was studied. A total of twenty-four S5BC1、S1BC5and BC4hybrids which came from4independent somatic hybrid regenerated plants were firstly biological characterized. Sixteen plants with a morphology resemble cauliflower were selected to be further characterized for their genetic background using multi-color FISH and molecular markers. Introgression lines and alien addition lines were clarified.Morphology of the24examined hybrids had a rich variation integrately in their stem, leaf and flower characters. These plants can be divided into3groups according to the morphology similarity:I, middle type;Ⅱ, leaning to cauliflower; III, resemble to cauliflower. Among them, type III has cauliflower traits not only in the vegetative growth stage, but also in the generative stage with a white hard flower head. DNA content and chromosome number in the cells of type III were all consistent with cauliflower, and the chromosome behavior in meiosis of PMC was almost normal.The plasmid DNA of CentBr (from Brassica rapa) and the genomic DNA of black mustard was labeled with Biotin-11-dUTP and digoxingenin-11-dUTP, resperctively. FISH analysis demonstrasted that there were7pairs of strong、2pairs of faint signals on cauliflower chromosomes, but no signal on black mustard genome using CentBr as probe; there were8pairs of strong signals on black mustard chromosomes, but one pair of signals occurred on cauliflower chromosomes using black mustard genomic DNA as probe. Sixteen plants selected from type II and typeⅢ were further characterized with FISH. Resuslts revealed that12plants had similar chromosome hybridization signals with cauliflower, which suggested that there were no intact independent black mustard chromosomes in the genome, and could be the introgression lines. Four plants were confirmed having different constitution of chromosomes from cauliflower and from black mustard, which were alien addition lines.SSR markers mainly selected from Brassica rapa10linkage groups were utilized for a further analysis on the genetic background of these plants. B.rapa and B. carinata were setting as contrast materials. A total of298bands were generated with65primer pairs, among which165were polymorphic bands. On average,2.5polymorphic loci were generated with each primer pair. The results showed that all the16plants, except one, had varied black mustard (B genome) specific bands. All materials had the symptoms of the losing of some cauliflower (C genome) specific bands and the occurrence of some specific bands from B. carinata genome. There were novel bands occurred in some of the plant samples.Based on the FISH and SSR analysis results, plants with18chromosomes and SSR loci fewer than3were selected for a further AFLP analysis. Results revealed that all the samples including that which had no black mustard specific SSR amplification had B genome specific and B. carinata specific AFLP bands; and also some cauliflower specific bands were, absent and some novel bands formed. |
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