Analysis On The Origin And Characteristics Of 'Hongrou Huyou'

Periclinal chimeras spontaneously or artificially occur and are valuable in horticultural crop breeding.A new mutant named‘Hongrou Huyou'was found during a bud sports investigation.Its fruit size,seed number and pericarp were similar to those of‘Changshan-huyou'?Citrus changshan-huyou?,and the color and flavor of the flesh were similar to those of the‘Owari'satsuma mandarin?C.unshiu?.This mutant was believed to be a grafted chimera between the C.unshiu and C.changshan-huyou.To verify this hypothesis,the morphology,flesh carotenoid content and molecular markers were evaluated in‘Hongrou Huyou'and the two hypothetical grafted donors so that we can clarify the origin and tissue origin of'Hongrou Huyou'.In this study,the leaf photosynthetic parameters were measured by LI-6400XT portable photosynthetic system.The fast chlorophyll fluorescence induction dynamic curve was determined by using M-PEA multifunctional plant efficiency analyzer.The chlorophyll content was determined by 95%ethanol extraction method and the fruit quality changes during development were measured.To explore the effects of heterologous epidermis on the photosynthetic characteristics and the fruit quality of‘Hongrou Huyou',we can provide a theoretical basis for synthetic chimeras.The results of this study indicate that:1.Characteristics of‘Hongrou Huyou'derived from L2/L3,such as the fruit size,winged leaf,seed,pollen,and rind aroma,were similar to those of‘Changshan-huyou',whereas the juice sac and stomatal characteristics originating from L1 were the same as those of the‘Owari'satsuma mandarin.High-performance liquid chromatography?HPLC?analysis of carotenoids from the flesh of‘Hongrou Huyou'showed that the content was the same as that of the‘Owari'satsuma mandarin,with?-cryptoxanthin producing the main carotenoid spectrum,whereas lutein and violaxanthin were the main carotenoids in‘Changshan-huyou'.Nuclear simple sequence repeat?nSSR?,chloroplast simple sequence repeat?cpSSR?and mitochondrial simple sequence repeat?mtSSR?analyses showed that the leaves,outer pericarp?epidermis and flavedo?,segment wall and juice sac of‘Hongrou Huyou'contained the nuclear,chloroplast and mitochondrial genomes of both donors;however,the albedo of‘Hongrou Huyou'only contained the genetic material of‘Changshan-huyou'.According to the morphological,carotenoid and molecular marker analyses,‘Hongrou Huyou'is confirmed to be a periclinal chimera that consists of L1 from C.unshiu and L2/L3 from C.changshan-huyou.2.The net photosynthetic rate?P_n?and intercellular CO₂ concentration?C_i?of'Hongrou Huyou'were9.83?molCO₂·m^-2·s^-11 and 322.12?molCO₂·mol^-1,respectively,which were not significantly different from those of‘Changshan-huyou',but significantly higher than those of‘Owari'satsuma mandarin.The stomatal conductance?G_s?and transpiration rate?T_r?of'Hongrou Huyou'were 0.32 molH₂O·m^-2·s^-11 and4.70 mmolH₂O·m^-2·s^-1,respectively,which were significantly higher than two donors.However,there was no significant difference in the maximum photochemical efficiency?F_v/F_m?among the three cultivars.Moreover,the performance index based on the absorption of light energy(PI_abs)and the comprehensive performance index(PI_total)of'Hongrou Huyou'were 4.98 and 1.63,respectively,which were not significantly different from'Changshan-huyou',and both of them were significantly lower than‘Owari'satsuma mandarin.Meanwhile,the fast fluorescence induction dynamic curve,the phenomenological energy fluxes per RC and CS,relative variable fluorescence at J-step?V_J?,quantum yield of'Hongrou Huyou'were similar to that of‘Changshan-huyou',reflecting that the homology and homogeneity of chlorophyll fluorescence mechanism were similar between them.The content of chlorophyll b?1.18mg/g?of'Hongrou Huyou'was similar to that of'Changshan-huyou',which was significantly higher than that of‘Owari'satsuma mandarin,the content of chlorophyll a?2.51mg/g?was significantly higher than satsuma mandarin and significantly lower than'Changshan-huyou'.The higher chlorophyll content of'Hongrou Huyou'and'Changshan-huyou'may be one of the reasons for the high net photosynthetic rate.3.The pericarp color,thickness and hardness of'Hongrou Huyou'were similar to those of'Changshan-Huyou',the flesh color and solid acid ratio were similar to those of‘Owari'satsuma mandarin.Additionally,the changes of fruit weight and Vc content were between its donor plants,but the content of soluble solids in'Hongrou Huyou'was significantly higher than that of the two donors.‘Hongrou Huyou'combines the valuable characteristics of both donor plants and may become a new variety in the citrus fresh market.