Translocation Lines Identification In Progenies Of Chinese Cabbage-cabbage Alien Addition Line AC₄ And Expression Of Genes Related To Head Development

Chinese cabbage(Brassica rapa L.ssp. Pekinensis, AA) is one of the most important vegetable crops in China, belonging to Brassica rapa species of Brassica genus in Cruciferae family. Heading Cabbage(Brassica oleracea var. capitata CC) is also a member of Brasscia genus in Cruciferae family, with specific characteristics by nutrients, heading and resistance compared to Chinese cabbage. New germplasms including A-C genome addition line and translocation line could be produced by introduction, recombination and translocation between A and C chromosome because of their high homology. In the present research, Chinese cabbage-cabbage monosomic addition line AC4 and microspore culture plants(doubled haploid) derived from AC4 selfing progenies were used as materials to investigate the phenotypic traits and to identify chromosome fragment of cabbage, from which 537 microspore plants with cabbage chromosome fragment were obtained. Combining with chromosome counting, three translocation lines of Chinese cabbage-cabbage were identified. Furthermore, expression of genes related to heading was performed in selected different progenies of translocation lines. This research will provide an important reference for the screening and identifying of Brassica translocation lines, and will offer important materials for creating new germplasm in Chinese cabbage.1. In total 1239 In Del markers distributed in 9 linkage groups were used to amplify AC4 and its parents, 1039 of them was polymorphic between Chinese cabbage and cabbage, with 79.98% of polymorphism. In AC4, 184 polymorphic In Del markers could amplify exogenous bands of Cabbage, involving 5 linkage groups of mainly C05 and part of C08、C02、C03 and C04.2. Forty four polymorphic markers were used to identify 537 microspore plants of AC4, resulting of 1-13 cabbage genomic segments for all plants. The most of plants had nine fragments, with 13.97% of percentage; the less of plants had seven fragments, with 1.30% of percentage; 13 plants had one fragment, with 2.42% of percentage.3. Sixteen traits of leaf shape, leaf color, bugs size and petal shape at reproductive growth stage were compared and analysised in AC4 and its progeny plants derived from microspore culture. Different degrees of variation in traits related to basic leaf and flower was observed. Within progeny population, we found some traits present in cabbage, in which the trait of none foliar hair had the highest ratio of 44.64%. Principal component analysi indicated that accumulated loading value of six main components was 63.23%, in which the percent variance explained of principal component 1 was 23.10%. Traits of leaf size and flower related contributed most to phenotypic variation.4. Chromosome number of three microspore plants(B3-29, C4-13 and qdh-52) with small cabbage chromosome fragment were counted at reproductive growth stage, resulting of chromosome number 2n=20, which were identified as translocation lines. The exogenous cabbage chromosome fragments were identified by In Del markers in the 1st generation of selfing population, indicating that the Cabbage segment of each selfing plant in three populations was consistent with parental microspore plants present polymorphism in cabbage. The exogenous cabbage chromosome fragments had good stability.5. In the 2nd generation of selfing population for above three translocation lines, 12 traits at harvest stage were investigated. In B3-29, transgressive segregation for head height and costa length. In qdh-52, six traits such as head color and head top shape had similar to cabbage. In B3-29 and qdh-52, four types of heading formation were observed overlapped, folded, middle and irregular type. The measurement of main nutritional components indicated that the content of dry matter, vitamin C and soluble sugar in qdh-52 were higher of Ca, Mg, K and Cu was higher than in two parents. Furthermore, eight glucosinolates were found in the used three translocation line populations that present in Chinese cabbage 85-1.6. In the 2nd of selfing populations of B3-29 and qdh-52 with head type variation(overlapped, middle and folded type), eight genes related to auxin and organ formation were used to perform q RT–PCR anlalysis at three different stages(rosette, heading and harvest stage). Each of eight genes expressed at all different stages in two populations. In folded type, with plant development expression of genes GA2OX5 and GA5 was decreased, reaching the highest at rosette stage. The expression of RCD1-2, CDR1, KAN2 had the highest level at heading stage, resulting a trend from increasing to decreasing with plant development. In middle type, the expression pattern of KAN2 had similar trend with it in folded type, reaching the highest at heading stage. The expression level of two genes of NLM9-1, NLM9-2 had the highest value at rosette stage for three types of materials, without any effects by types.7. For above eight genes and three different types, gene expression was analysis at different leaves growing from outside to inside. Results indicated that each of eight genes expressed at all different parts in two populations. In B3-29, GA2OX5, RCD1-2 and KAN2 kept high expression level in outside leaf, and expression decreased from outside to inside leaf. The expression of NLM9-1 and NLM9-2 from outside to inside leaf had a trend from increasing to decreasing. In qdh-52, NLM9-1, NLM9-2 and KAN2 had low expression level in outside leaf in overlapped and middle types, with increasing trend from outside to inside leaf. In folded type, expression patter of above three genes was different, with a trend from increasing to decreasing. In folded and middle types, two genes of SGT1 B, GA5 had the highest expression level in inside leaf, with increasing trend from outside to inside leaf.