Effects Of Factors On Quality And Fatty Acids Synthesis Of Torreya Grandis ’Merrilli’ Seeds During After-ripening Period

Torreya grandis ‘Merrilli’（T.grandis ‘Merrilli’）belongs to the genus of Torreya,and T.grandis ‘Merrilli’ seed is one of the rarest dry nuts unique to China.It’s highly loved by people due to it’s unique flavor,high nutritional and medicinal value.The objectives of this research were to investigate the effects of harvest maturity,after-ripening way,temperature and height on quality and fatty acid compositions of T.grandis ‘Merrilli’ seeds during after-ripening period.It is helpful to improving T.grandis ‘Merrilli’ products quality and after-ripening technology by exploring changes in related enzymes and expression levels of genes in this process.The main results were as followed:（1）Seven key genes in fatty acids synthesis pathway were obtained by transcriptome analysis and gene screening,and named Tg FAD3₁8460,TgFAD3₂3658,TgFAD2₂5920,Tg FAD2₁7606,TgFAD2₂1048,Tg ACC₁4355 and TgACC₂3575,respectively.（2）Compared with nearly-matured seeds,the matured seeds have higher levels of protein,oil and unsaturated fatty acid,lower starch contents,indicating that matured seeds have better quality.As the maturation progressed in seeds,the activities of ACC,FAD2 and FAD3 increased significantly whereas FAS activity changed little.The changes in the related expression levels of genes were consistent with those of enzyme activities.（3）T.grandis ‘Merrilli’ seeds finished the after-ripening process when treated with traditional two-time after-ripening way for 21 d,which the contents of oil,protein and unsaturated fatty acid increased markedly,starch and soluble sugar content decreased,the distance between seed kernel and coat increased and the colour of seed coat turned from red to black.Compared with two-time after-ripening way,T.grandis ‘Merrilli’ seeds could finish the after-ripening process with one-time after-ripening way for 14 d,meanwhile the ripening time was shortened about 7 d and the contents of unsaturated fatty acid,sugar,oil and protein had no significant different from those of two-time after-ripening way.（4）Ripening at 4℃ for 42 d had no significant effect on starch,soluble sugar,protein,oil and unsaturated fatty acid content of T.grandis ‘Merrilli’ seeds compared with ripening at normal temperature（25℃）.However,low temperature ripening could delay the after-ripening process of T.grandis ‘Merrilli’ seeds,which is mainly manifested as the decline of starch and soluble sugardecomposition rate and decrease of protein and oil increasing.Also,low temperature ripening could increase FAD2 activity,decrease the activities of ACC,FAS and FAD3,and increase the expression level of TgFAD2 gene,decrease expression levels of TgACC and Tg FAD3 genes,which was consistent with those of enzyme activities.（5）T.grandis ‘Merrilli’ seeds ripened under height 25±2cm had lower contents of soluble sugar and starch,higher levels of protein,oil and unsaturated fatty acid than those under 15±2cm and 35±2cm,which would provide guidance for after-ripening technology in T.grandis ‘Merrilli’seeds.