Effects of Different Transplanting and Harvest Dates on Yield and Quality of Flue-cured Tobacco Leaves

In this study,the effects of nine different combinations of transplanting and harvest dates on yield and quality of flue-cured tobacco leaves were investigated.The results showed that different combinations of transplanting and harvest dates had few effects on growth period and agronomic characters of tobacco plants but exerted remarkable effects on economic characters and chemical composition of flue-cured tobacco leaves.With the postponing of transplanting stage,output value of flue-cured tobacco leaves increased.Output value of flue-cured tobacco leaves in C1treatment（normal harvest） was higher than that in C2（harvest 7 d later） and C3（harvest 14 d later） treatments.Different combinations of transplanting and harvest dates had significant effects on chemical composition of flue-cured tobacco leaves,which exhibited no obvious law.Overall,flue-cured tobacco leaves in T3C1treatment（transplanting 14 d earlier,normal harvest） displayed excellent performance compared with other treatments.

Natural variations in MdNAC18 exert major genetic effect on apple fruit harvest date by regulating ethylene biosynthesis genes

Dissecting the genetic control of apple fruit harvest date(AFHD) into multiple Mendelian factors poses a significant challenge in modern genetics.Here,a quantitative trait locus(QTL)for AFHD was fine-mapped to the NAC transcription factor(TF) MdNAC18 within the interval defined by the overlap of QTLs Z03.5/Z03.6 and F03.2/F03.3.One direct target of MdNAC18 is the ethylene biosynthesis gene MdACO1.The single nucleotide polymorphisms(SNPs) SNP517 and SNP958 in the MdNAC18 coding sequence modulated activation of MdACO1by MdNAC18.SNP1229 in the MdACO1 promoter destroyed the MdNAC18 binding site and thus abolished MdNAC18 binding.SNP517 and SNP958also affected MdNAC18 activation of the TF gene MdARF5;MdARF5 activates the ethylene biosynthesis gene MdACS1.SNP517 and SNP958 in MdNAC18,SNP1229 and SNP769(linked to In Del62) in MdACO1,and In Del162 in MdACS1constituted a genetic variation network.The genetic effect of this network on AFHD was estimated as60.3 d,accounting for 52.6% of the phenotype variation of the training population.The joint effects of these polymorphisms increased the accuracy of a genomics-assisted prediction(GAP) model for AFHD(r = 0.7125).Together,our results suggest that genetic variation in MdNAC18 affects AFHD by modulating ethylene biosynthesis and provide an optimized GAP model for apple breeding.