Genetic Variation Research In The Early Period Of Arachis Allopolyploidization

Genetic variation mechanism during allopolyploidization were studied to understand the allpolyploidy evolutionism in Arachis. We used the early allopolyploidy generations including the triploid F1and the polyploid So～S3of the interspecific hybridization between tetraploid cultivated peanut Zhongkaihua No.4and diploid wild peanut A.chacoensis to research the phenotypic and cytological characters variation; to analyze the physiological and biochemical variation related to disease resistance; to research the genome changes including varied time, types and frequency by SSR and SCoT; to study the gene expression changes including varied time, tendentiousness, types and the expression-varied gene sequence characters by cDNA-SCoT and cDNA-HFO-TAG. It is significant of accomplishing the research to realize the regularity of phenotypic, cytoiogical, physiological property and genetic variation during allopolyploidization in the Arachis, to reveal the peanut allopolyploidy evolution mechanism and rich the evolutionism of species, also to utilize the good gene of wild germplasm. The main results were summarized as follows:1. The phenotypic and cytological traits variation researches in the early period of allopolyploidization in Arachis interspecific hybridization.The research results on some morphological and cytological characters of the hybrid F1and allopolyploid generations (So-S3) indicated that the calyx tube length, corolla width, pod length, No.1lateral branches and total number of branches showed obviously instability and the coefficient of variation in the Fi-S3generation was high with12.37%,13.74%,27.75%,34.56%and48.48%respectively. Along with the generation self, the traits of diploid wild peanut as male were steadily declined but of the female increased, which was obviously partial maternal inheritance. Furthermore, the four spore frequency, the stained and germinated capability of pollen, and the fertility increased along with the self-cross course, which provided support for producing more fertile progeny.2. The physiological property variation researches in the early period of Arachis allopolyploidization.The research results of POD activity, proline content, MDA content, soluble sugar content and chlorophyll content of the leaves of hybrid Fj and allopolyploid generations (So-S3) showed that the physiological property indicator connected with resistance of wild male peanut were higher than cultivated female. There was obviously heterosis in the hybrid F1whose indicator were higher than progenitor expect soluble sugar content. Furthermore, after chromosome doubling, POD activity, proline content and chlorophyll content of So were higher than F1, which indicated that allopolyploid had better environmental suitability and resistance capability such as disease resistance and drought tolerance.3. The genome variation researches in the early period of Arachis allopolyploidization.The genomes variation of early polyploidy generations was researched by SSR and SCoT molecular technique in Arachis interspecific hybridization. During the early period of allopolyploidization, the genomes were prone to change fast as early as in F1and kept altering after chromosome doubled and in the process of selfing. The changes mainly included the appearance of novel fragments, loss and simultaneous appearance of parental bands. Along with the self-cross course, the loss frequency of fragments from male was rather higher than from female. The results indicated that the ATG translation start codon, the microsatellites and the flanking region varied fastly, extremely and extensively in early allopolyploidization period of the hybridization which speculated that their biological function might be related with polyploidy evolution and stability.4. The gene expression changes research in the early period of Arachis allopolyploidization.The gene expression alteration of early polyploidy generations was studied in Arachis interspecific hybridization by cDNA-SCoT and cDNA-HFO-TAG techniques. The genes expression changes began as early as in F1and along with the process of self-cross, mainly included new gene activation and the gene loss absolutely or partly from progenitor. And the frequency of gene loss or silence from male was higher than from female. The gene of expression changed were including resistance-related genes, retrotransposon-related genes, energy and metabolism-related genes, unknown functional protein-related genes, signal transduction-related genes, transcription factor-related genes and unknown functional protein. The results indicated that rapid changes of gene expression happened in the early period of peanut allopolyploidization, that the gene expression variation in Arachis and other species can be analyzed with cDNA-SCoT and cDNA-HFO-TAG techniques.