Molecular Marker Analysis Of Parents And Their Semi-sib Progenies For The Reproduction In Hickory

Hickory is an important non-timber species in Zhejiang Province and there is no cultivar under this species. Studies conducted in recent years have shown that apomixis exists in hickory cytologically and polymorphism is low in natural population through molecular marker analysis of genomic DNA. To this end, research on hickory reproduction was conducted based on the establishment of a study population that is composed of a parent population and its half-sib progeny . The results are as follows:1. A study population of 440 individuals has been established, which is composed of 40 individual parent trees from a natural population and 10 half-sib progeny from open pollination each parent tree; it has been found in seeding that 4.04% of all the germinated seeds are double-embryo seeds.2. A SRAP protocol suitable for hickory was established and three different molecular markers viz. RAPD, ISSR and SRAP were compared in hickory. It has been shown that SRAP and RAPD could be used in hickory.3. For random mating in a natural population, a data set of molecular markers and a likelihood function were established when outcross, apomixis and selfing were considered, respectively and EM algorithm was used to estimate unknown parameters including rates of outcross (ω), apomixis (θ) and selfing (1-θ-ω). Significance of outcross and apomixis occurrence was tested and computer simulation was performed for testing the statistical model in terms of two sample sizes (200 and 400). It is shows that the model developed can well estimate all the parameters, and the result is better when the sample size is increased.4. RAPD and SRAP were used to study the 440 samples. Totally199 loci were amplified, out of which 168 loci were polymorphic, accounting for 84.42% of the total. The real data analyzed with the model showed thatω,θand 1-θ-ωcould be estimated and the apomixes rate in hickory was around 32%, which indicated that apomixis exists at the DNA level in hickory.5. Four parent hickory trees and their double-embryo seedlings from 9 seeds were analyzed with 24 RAPD primers and 15 pairs of SRAP primers. As a result, no locus was amplified with all 24 RAPD primers but only a pair of SRAP primers viz. F6/R8 amplified one polymorphic locus at 400 bp, which was only available in double-embryo seedlings. Sequencing of the 400 bp fragment showed that the fragment was associated with a protein in relation to senescence and was not specific to double-embryo seedlings, which couldn't indicate any relationship between the locus and apomixis. It was thought that it is not complete apomixis in hickory.