| Peanut plays an important role in providing edible vegetable oil in China. Understanding the genetic diversity and allelic variation of genes responsible for important agronomic traits in peanut will greatly facilitate the utilization of peanut germplasm, and consequently accelerate the process of peanut genetic improvement. According to the method in core collection construction, we selected196peanut improved cultivars from the550cultivars developed in China during the past60years. Genetic diversity of196peanut cultivars was analyzed using SSR markers. Markers associated with oil content were obtained under multiple field conditions. Peanut AhDGAT3gene was cloned and its genetic diversity was also analyzed. The research results will provide theoretical basis for high oil content peanut cultivar development. The main results are summarized as follows.1. One hundred and forty-six highly polymorphic simple sequence repeat (SSR) markers were used to assess the genetic diversity and population structure of196peanut cultivars that were widely used in different peanut growing regions in China. These SSR markers amplified440polymorphic bands with an average of2.99per primer, and the average gene diversity index was0.11. Eighty-six rare alleles with a frequency less than of1%were identified in these cultivars. The largest Fst or genetic distance was found between the cultivar group that were mainly collected from the south regions and those from the north regions in China. A neighbor-joining tree of cultivars in different ecological regions was constructed based on pairwise Nei’s genetic distances, which showed significant difference between cultivars from these two different regions. A model-based population structure analysis divided these peanut cultivars into five subpopulations (Pla, Plb, P2, P3a and P3b). Pla and Plb include cultivars from the southern provinces including Guangdong, Guangxi and Fujian. P2population consists of the cultivars from Hubei, Shandong and Henan. P3a and P3b contained the cultivars from the northern provinces including Shandong, Anhui, Henan, Hebei, Jiangsu and Sichuan. The cluster, PCoA and PCA analysis based on the marker genotypes, revealed five distinct clusters for the entire population that is related to their cultivation regions.2. Association analysis of oil content, oleic acid, linoleic acid in different enviorments revealed that18markers were associated with oil content,7markers associated with oleic acid,10markers associated with linoleic acid in different environment. Eleven of18markers associated with oil content were found to be located in6linkage groups (A03, A04, A07, A10, B04and B07). Three markers were distributed in A07and A10linkage group, respectively. In2011,4markers were repeatedly observed in two different environments.3markers associated with oil content have larger effect value:markers GA24with2.22in Yuhua9326and Zhonghua15, AC1C11with4.97in wanhua7and ehua2, and Seq1E6with1.66in Yuhua9326and Zhonghua15. Six out of the7markers were found to be associated with oleic acid content, which was the same with markers associated with linoleic acid. Markers Seq1B9and TC4F10associated with oleic acid content were detected in two environments in2011. Marker Seq4E10associated with linoleic acid were detected in different environments. Markers with larger effect value were markers GM2246, HAS0969and Seql19, and its value was16.70,6.33and15.37, respectively. The carrier is the high oleic variety Kainong H03-3. Markers TC4F10and Seq4E10values were12.69and7.23, and the corresponding vector Suiningerwo and Ehua2, respectively. Therefore, these markers associated with oil content, high oleic acid will greatly facilitate marker assisted selection breeding.3. Sequence analysis of peanut AhDGAT3indicated that3different types of AhDGAT3were present in peanut genome, namely AhDGAT3-1, AhDGAT3-2and AhDGAT3-3, respectively. The coding sequence of AhDGAT3-1was the same with gi/58324011, with a1020bp coding sequnce encoding339amino acids. AhDGAT3-2and gi/62084564had the same sequence, with1038bp coding region, encoding345amino acids. The coding region of AhDGAT3-3is1026bp, encoding341amino acids. There had more12bases in501-512positions and6bases in588-594positions of the coding region in AhDGAT3-1than AhDGAT3-2and AhDGAT3-3. And there had more6bases in AhDGAT3-3than AhDGAT3-1and AhDGAT3-2in193～198position encoding region. In86SNP loci,8SNP loci associated with high oil content were acquired, which ranged from18%to45%in explanation rate of oil content. Analysis of associated SNP markers, there had a synergistic effect on the oil content in85(A-G),109(A-C),915(A-G) replacement, and those effect value was1.5,1and1.5, respectively. The corresponding vector was Ehua2. |
