| Fruit color is an important trait and suugesting the physiological and biochemical state of fruit.Abundant light can facilitate fruit coloring by promoting rapid accumulation of secondary metabolites such as anthocyanin during fruit development.Ethylene,as an important natural plant hormone,plays an important role in regulating the ripening process of apple fruit.However,the relationship between ethylene and light during fruit coloring is still unclear.In this study,we conduct light,continuous darkness,ethylene and 1-MCP treatment on two apple cultivar with different ethylene sensitive,and we estimated anthocyanin content,ethylene release rate,expression level of anthocyanin and ethylene biosynthesis gene,the main results are as follows:1.Light promotes fruit coloringWe conducted light and dark treatment on ethylene sensitive cultivar ‘Stolav’(140 days after flowering)and ethylene insensitive cultivar ‘Red Fuji’(140 days after flowering).Apple fruit were sampled in 0,3,5,8,12 days,respectively.HPLC(High Performance Liquid Chromatography)results showed that light promote anthocyanin accumulate in apple fruit,and no significant anthocyanin were detected in apple fruit under dark treatment.The ethylene content in the fruit was determined by gas chromatography.It was found that the ethylene release increased gradually with the treatment time,and the ethylene release rate of the apples treated with continuous darkness was higher than that in apple treated with light.Quantitative real time(q RT)-PCR results showed that the expression level of anthocyanin biosynthesis genes displayed increased first and then decreased trend,and the expression level of ethylene biosynthesis genes gradually increased with light treatment.The expression level of anthocyanin biosynthesis genes remain a lower level under dark treatment.And transcription level of ethylene biosynthesis genes also showed an increased first and then decreased trend,and also higher than that in light treatment.The phenotype and relate data showed similar trend in these two cultivars.2.Ethylene treatment under light promotes fruit coloringThe results showed that the color of the two apple cultivars were significantly accelerated after ethylene treatment.HPLC results showed that the content of anthocyanin in the fruit treated with ethylene was significantly increased,which was higher than that in fruit treated with light.Gas chromatography showed that the release rate of ethylene increased after ethylene treatment,and the ethylene content was higher than that in fruit under light treatment.q RT-PCR results showed that the expression levels of anthocyanin biosynthesis genes and ethylene biosynthesis genes were significantly increased after ethylene treatment,which was significantly higher than that under light treatment.3.1-MCP treatment inhibit fruit coloring under light conditionThe results showed that 1-MCP treatment significantly inhibited fruit coloration.HPLC results showed that the content of anthocyanin in fruit treated with 1-MCP was significantly lower than that in fruit treated with light.Gas chromatography analysis showed that 1-MCP treatment inhibited the release rate of ethylene,and ethylene content was lower than that in fruit under light treatment.q RT-PCR results showed that the expression levels of anthocyanin biosynthesis genes and ethylene biosynthesis genes were significantly decreased after 1-MCP treatment,which was significantly lower than that in fruit under light treatment.4.Ethylene treatment not promote fruit coloring in the darkThe results of ethylene treatment showed that ethylene treatment could not promote the color of apple fruits under dark condition.HPLC results showed that the content of anthocyanin in apple fruit treated with ethylene and dark treatment were not detected.Gas chromatography results showed that ethylene treatment promoted the release rate of ethylene,and the ethylene content was higher than that in fruit under dark treatment.q RT-PCR results showed that anthocyanin biosynthesis genes were significantly increased after ethylene treatment,and the expression level of ethylene biosynthesis genes was increased and higher than that in fruit under dark treatment.5.1-MCP treatment not promote fruit coloration in darknessWe also conducted 1-MCP treatment on two cultivars under dark condition.The results showed that there are no coloring in the apple fruit.HPLC results showed the anthocyanin contents were not detected in apple fruit under dark and 1-MCP treatment.Gas chromatographic analysis showed that1-MCP treatment inhibited the release rate of ethylene,and ethylene content was lower than that in fruit under dark treatment.q RT-PCR results showed that the expression levels of anthocyanin biosynthesis genes and ethylene biosynthesis genes were significantly decreased after 1-MCP treatment,and the expression levels were lower than that in fruit under dark treatment.In conclusion,ethylene treatment can significantly promote anthocyanin accumulation under light condition,but not under dark condition,indicating that light is a necessary factor for fruit coloring,and light can promote anthocyanin accumulation by regulating ethylene biosynthesis.It is great significance to study the effects of environmental conditions and hormones on apple fruit coloring for improving apple fruit quality. |
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