Genetic Diversity Analysis And Homozygous Line Construction Of Wild Monoembryonic Hongkong Kumquat

Because of the long juvenile period, highly heterozygous genetic background and polyembryony, it’s difficult to obtain the hybrid offspring by conventional hybridization technology in citrus. Besides, it’s difficult to confirm the function of candidate gene by transgenic technology. Fortunella has a long cultivation history in the original centre China, and it is one of the important germplasm resources of citrus. The HongKong kumquat(Fortunella hindsii Swingle) of Fortunella genus can serve as the material of genetic transformation, because of its small size, short juvenile period, as well as blossom and yield fruit of seedling in about one year. It was first found that kumquat includes monoembryonic genotype and polyembryonic genotype in our previous study. Homozygous monoembryonic line could be acquired with anther culture. On one hand, it can provide materials for conventional breeding, and shorten breeding circle. On the other hand, it can be used for function genomics. The main research materials are wild monoembryonic kumquat and partial triennial polyembryonic kumquats, aiming at studying genetic diversity of wild monoembryonic resources, and trying to obtain homozygote through anther culture. Also, this paper compared the transformation efficiency of different lines. The main research results are as follows:1. In 2011 and 2012, more than 50 monoembryonic plant samples were totally collected in the mountains, Then their genetic diversity were analyzed, these lines were preserved in citrus repository of Huazhong Agricultural University.2. Using the methods of SSR, the samples collected in 2011 were analysed.28 markers in 9 chromosomes were selected. Among 35 monoembryonic individual plants and 5 control lines, sample 6-7 have the highest homozygosity by 86.67%, and it can reach to 99.8% after 6 generations’self-fertilization theoretically; the lowest line has only 47.06%. Besides, the homozygosity of each locus in 9 chromosomes were analysed, the highest average homozygosity was No.3 chromosome, next one was No.2 chromosome.3. In 2012, By bagging for monoembryonic kumquat located in Huazhong Agricultural University, the first self-fertilization generation plants of the whole materials were acquired at present. To ensure the feasibility of selfing, test for homozygosity of each generation from three selfing lines have been conducted by SSR, and the results shows that kumquat can be purified by selfing, because homozygosity of each generation from three selfing lines gradually increased, the homozygosity of sample LT parent(So), selfing generation one(S1) and selfing generation two(S2) were 37.5%、 50%、62.5% respectively; the homozygosity of sample 1-15 were 62.5%、62.5% respectively; the homozygosity of sample were 62.5%、75%、75%.4. During May to October in 2012, a total of 10,000 monoembryonic and polyembryonic kumquat anthers were cultured, however, most of them had no germination and only three grew callus.5. By selecting monoembryonic genotype and polyembryonic genotypes, from 9 different areas, their transformation efficiency were studyed, By observing the proportion of resistant buds through fluorescence microscope, the result showed that sample F had the highest transgenic efficiency, the transformation efficiency of monoembryonic type was lower than polyembryonic type, and emerged more positive callus in transgenic process.