Obtaining Of F₁ Hybrid And Its Induced Epigenetic Variation Between Raphanus Sativus L. And Brassica Alboglabra Bailey

Distant sexual hybridization in plant is one of the most important technique for genetic research and genetic improvement.Wide hybridization can combine adaptability of parents or create new adaptability,that can also enrich gene pool,widen habitats, enhance genome evolution,synthesize new species.Wide hybridization and subsequent genome doubling(polyploidy) often induce an array of genetic and epigenetic variation.F₁ plants from intergeneric hybrids between Raphanus sativus L.(2n=18,RR) and Brassica alboglabra Bailey(2n=18,CC) were obtained by hand cross and embryo rescue. Random amplified polymorphic DNA(RAPD) markers were used to identify F₁ plants. 11 random primers screened from100 used to identify F₁ plants.The hybrids produced specific bands of parents or new bands absent in both parents.RAPD results indicated that F₁ plants were obtained from Raphanus sativus L.(2n=18,RR) and Brassica alboglabra Bailey(2n=18,CC).Southern blot analysis after restriction endonuclease digest of rDNA showed that DNA methylation changes of 45S rDNA were observed among parents and offsprings.The methylation level of 45S rDNA declined first and then increased during passaging.While those of 5S rDNA showed few difference,indicating that epigenetic variation of 45S rDNA was happened during hybrid formation and passaging,while the epigenetic inheritance of 5S rDNA is stable.The genomic DNA methylation pattern of parents and F₁ plants was assessed using the methylation-sensitive amplification polymorphism(MSAP).The results indicated that there existed some cytosine methylation patterns differing between the hybrid and its parents.83.27%methylation types could be stablely transmitted from one generation to the next.A small part represented an increase or decrease in the level of methylation in the hybrid compared to the parents respectively.Demethylation occupied the main position during hybrid formation.Wether demethylation or hyper-methylation may be favorable for heterosis.The results of DNA methylation pattern of parents and F₁,F₄,F₁₀ plants using MSAP showed that 71.21%methylation types could be stablely transmitted from one generation to the next.In addition,demethylation and hyper-methylation were happened during passaging.The methylation level of some other methylation types was declined first and then increased or increased first and then declined during passaging.The results indicated that the methylation level of some genes changed during hybrid stability.This may be the result of mutual stability and mutual coordination of two genetic systems.