Research On Genetic Basis Of Bud Mutation Of Soft-seed Pomegranate

The genetic basis of bud mutation of soft-seed pomegranate was explored, based on seed characteristics,micro-structural feature of blade epidermis,isozyme and karyotype of chromosome in four pomegranate cultivars from Huaiyuan county in Anhui province. The theoretic basis of studying on resources and cultivation of the excellent pomegranate cultivars would be offered from the research results. The main results were as follows:1.The difference of seed quality among four pomegranate cultivars was compared. The result showed that there are many differences in exterior morphology of fruits and color of seeds. While there were many differences in weight and water content of seeds. The seed weight and water content of the new variety"baiyu"were higher than other cultivars because it had more affluent store substances. However the germination percentage of"baiyu"was the lowest in the four cultivars.2. Micro-structural feature of blade epidermis for four pomegranate cultivars was compared by scanning electronic microscope. The result showed that the stoma was constituted of two defended cells that was crescent-moon type. The stoma which appeared oval or egg-round arranged in the lower epidermis with no rules. The surface of outside cover of stoma were almost smooth, while the inside cover of stoma were smooth,undulant or tooth-like. All blade epidermis of four pomegranate cultivars appeared net-veined and ripply. Meanwhile, remarkable difference of structure feature in lower epidermis can be observed ,including shape,size and permutation pattern of epidermis cells as well the shape,size and density of stoma in blades. However, the venation of the four cultivars were similar.3.The characteristic of peroxidase isozyme (POD)and esterase isozyme (EST)of four pomegranate cultivars have been measured, PRC with PAGE. The analysis and comparison of isozyme pattern demonstrated one similar characteristic pattern and abundant polymorphics. From the isozyme bands of four pomegranate cultivars, it was found that"baiyu"was similar to its maternal plant in isozyme bands, except for slightly differences in the amount of enzyme bands. This result explained that the two cultivars were intimate in affinity .However the genetic substance of the new variety was indeed altered after bud mutation. While"Yushizi"was similar to"dabenzi"in isozyme bands.4..In the paper, the chromosome amount of four pomegranate cultivars were counted by root tip squash method, and karyotype analysis of them was carried on.It was found that the chromosome number of the four cultivars all were 2n=18.And the karyotype of four cultivars all belonged to stebbins'2B type.The result explained that there was little karyological variation of chromosome among these cultivars.Butthe differences still exsisted. The karyotype formula of"baiyu"was 2n=2x=18=12m(2SAT)+4sm+2st and its maternal plant was 2n=2x=18=8m+8sm(2SAT)+2st, suggesting that"baiyu"was close to its maternal plant. The arm ratio of maternal plant exceeding 2 accounted for 11.11% of the total,while"baiyu"was 22.22%.It suggested that the former may be older than the later in phylogenesis.The karyotype formula of"yushizi"was 2n=2x=18=14m(2SAT)+4sm and"dabenzi"was 2n=2x=18=10m(2SAT)+8sm. These two cultivars were also intimate to each other. Based on the arm ratio exceeding 2 ,"baiyu"was maybe the youngest in the four cultivars. Based on the karyotype ,"baiyu"and its maternal plant were more unsymmetric than the other cultivars. All the pomegranate cultivars had two SATs in the same seat. The overall chromosome volume of four cultivars were different.