| The anthocyanin content in fruit skin is an important visual characteristic of fruit quality for commercial market. Many consumers are willing to pay more for the redder than the less colored fruits, because they associate better-colored fruits with better taste, ripeness, and flavor.5-Aminoluvulinic acid(ALA) is an essential biosynthetic precursor of all tetrapyrrole compounds such as chlorophyll, heme and vitamin B12. Wang and others suggested that exogenous ALA in concentrations of100-300mg·L-1could promote fruit coloration of apple when sprayed20days before harvest. Wang and others also approved the observation and found that ALA treatment induced transient increase of phenylalanine ammonia-lyase(PAL) activity, suggesting that ALA might induce anthocyanin biosynthesis de novo. However, whether the effect of ALA promoting on anthocyanin accumulation can be used in fruit production have not been reported. In this study, grape and apple were used to study the characteristics of anthocyanin accumulation and regulation of exogenous ALA at eight different ecological apple orchards in China. In addition, ALA promotion on anthocyanin was found to be dependent on its conversion into tetrapyrrole compounds. The main results are as follows.1. In the first part of work, experiments were conducted with’Summer Black’and ’Jumeigui’table-grapes planted in plastic tunnels with rooting-zone restriction at young berry development period to study the effects of ALA with different concentrations(0.05,0.5and5mg-L"1) on fruit growth and quality. The results showed that all treatments could significantly increase the growth of leaves, the content of anthocyanin, the total soluble solids and the soluble sugars, and significantly decrease the titratable acid. Compared with control, the treatment of0.5mg·L-1was considered to be the best. It can increase anthocyanin content about119%and soluble sugars60.06%respectively. In addition,’Beniyoshi’grapes with root restriction cultivation were treated by ALA at doses of50,100,150and200mg·L-1at the verasion stage to test the effect on fruit coloration and quality. The results showed that all treatments could significantly increase the content of anthocyanin. Compared with control, the treatments of100and150mg·L-1could increase anthocyanin content about122%and71%respectively, which were considered to be the best treatments. ALA treatments also significantly increased the content of total soluble solids and the soluble sugars, and significantly decreased the titratable acid content. Therefore, the ratio of total soluble solids to titratable acid increased. The treatment of100mg/L could increase soluble sugars content about21%and ratio of total soluble solids to titratable acid about24%respectively, which was considered to be the best.2. In this part of work, the ’Kyoho’ grape fruits were treated by ALA at doses of50-200mg·L-1at the verasion stage to study the effect on fruit growth, anthocyanin accumulation in skins and fruit quality. The results indicated that ALA application at100-200mg·L-1significiently increased anthocyanin content regardless of intact or detach. Additionally, ALA treatment significantly promoted the fruit growth and quality. Detection by semi-quantitative RT-PCR showed the expression of genes including PAL, CHS, CHI, DFR, UFGT, MYB, bHLH and WD40. Light could promote the expression of the genes. Treatments with100-200mg·L-1ALA could significantly increase the expression levels of CHI, DFR, UFGT, MYB and bHLH, suggesting that ALA could regulate anthocyanin accumulation at molecular levels in grape skins.3. In this work, it was found that when ALA solution was sprayed to ’Fuji’ apple(Malus x domestica Borkh.) fruits20days before harvest at eight different ecological apple orchards in China, the anthocyanin accumulation on the skin and quality of fruits were significantly promoted by ALA treatments. Additionally, ALA treatments also promoted increase of anthocyanin content in the skin of detached apples exposed in a growth chamber. Analysis by semi-quantity RT-PCR showed that ALA could induce expression of anthocyanin biosynthetic genes, including the structure genes Pal, Chs, Dfr and Ufgt, and regulatory genes as well as Myb, bHLH and Wd40. However, when levulinic acid(LA), an inhibitor of ALA dehydrase, was added, the promotion of ALA on anthocyanin accumulation and the up-regulation of gene expression were all depressed. Therefore, ALA regulation on anthocyanin accumulation in apples was involved in up-regulation of gene expression, which might depended on ALA conversion into porphyrins. |
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