Creation Of New Peanut Germplasm With High Oleic Acid Using MAS Backcross Technology And The Genetic Effect Of AhFAD2 Gene

Peanut?Arachis hypogaea L.?is one of the most important economic and oilseed crops in China.It occupies an important position in the national economy.Peanut,with the high yield and high oil content,plays an important role in increasing the income of farmers and ensuring the supply of vegetable protein and oil.With the improvement of people's dietary structure and a variety of peanut products,higher demands are constantly made on the nutritional value and antioxidant properties of peanuts,while high-oleate?HO?peanuts with high nutritional value and strong resistance to oxidation are increasingly occupied international market.However,the HO peanut industry started in China late.The HO peanut varieties developed now have a lower market share compared to the normal oleate?NO?peanut and cannot meet the market demands,which is one of the most severe challenges of domestic peanut industry.Therefore,transforming the elite peanut cultivars with normal oleate?NO?into high oleate ones effectively,and learning the genetic effects of AhFAD2 controlling peanut high oleate trait,have important practical significance for speeding the HO peanut industry in China.In this study,a back-crossing approach combined with marker-assisted selection?MAS?was established and utilized to develop the HO variety.Four backcrosses were made by using the elite variety Zhonghua16?ZH16?,Zhonghua21?ZH21?,Quanhua551?QH551?and Xuhua13?XH13?as the recurrent parent?female parent?,as well as the the Jihua13?JH13?as the high oleate genes donor.Finally,the improved lines with HO trait and the most similar agronomic trait same as the recurrent parents were identified.Additionally,the selected BC₄F₃ generation materials of Zhonghua16 were selected to carry out research on the changes of fatty acid composition in peanut seeds caused by AhFAD2 gene mutation.The results of the study are as follows:1.By using backcross,off-season planting for additional generation in 1 year and molecular marker selection to quick and precious identification of target parent,the 4 peanut cultivars with normal oleate were successfully and quickly transited into high oleate ones within 3 years.And by evaluating their agronomic traits,quality and bacterial wilt resistance,several high oleate peanut cultivars were obtained,which were highly consistent with their corresponding recurrent female parent.The lines ZJ019,ZJ109,ZJ160 and ZJ805 of the 4 backcross progenies with oleic content as 82.54%,79.85%,79.22%and 78.94%,are regarded as improved HO new germplasms of ZH16,ZH21,QH551 and XH13.2.Gas chromatography was used to determine the 8 main fatty acids composition in peanut seeds of BC₄F₃ generations obtained from the backcross of ZH16 and JH13.The significant negative correlation between oleic and linoleic acid?r=-0.995?as well as palmitic acid?r=-0.924?were found,while it showed positive correlation between oleic acid and arachidonic acid?r=0.605?.It was found that when the oleic acid content in peanut seeds reached 80%,the palmitic acid content was reduced from 12%to 6%,arachidonic acid content was increased from 0.72%to 0.99%.The AhFAD2 gene has direct regulation on the oleic and linoleic acid as well as indirect regulation of palmitic acid,which tend to show pleiotropism.3.Using the near-isogenic lines of high oleic/normal oleic acid traits,a multiple comparison of the oleic acid content of different AhFAD2 genotypes in peanuts was conducted,and it is further clarified that the peanut oleic acid trait is controled by incomplete dominance of AhFAD2A and AhFAD2B,showing cumulative effect and equal contribution,as well as oleic acid content gradually increasing with the increase of recessive allele numbers of AhFAD2?...