Effect of jasmonates on coloration and quality of the‘Christmas Rose’ grape berry

Objective:

TheChristmas Rosegrape is a type of the late-maturing cultivars which is widely planted in China. It is favored by consumers because of its delicate fleshresistance to storage and transportationand high quality. Howeverin some areasthe coloration of theChristmas Rosegrape was not very good because of high temperature and humiditywhich affected its internal and external qualities. In recent yearsresearchers found that jasmonateswhich widely exist in plantscould improve coloration of fruit by promoting the accumulation of anthocyanin. This study is to explain the effect of different concentrations of exogenous prohydrojasmon(PDJ)methyl jasmonate(MeJA) on the coloration and quality of theChristmas Rosegrape so as to provide some theoretical evidence to improve coloration and quality of this grape berry.

Methods:

The trial was conducted at the experimental farm of the Zheng⁃zhou Fruit Research InstituteCAASon uniform 6- year- oldChristmas Rosegrapevines. All treatments were applied in three replications and arranged in a complete randomized block designwith a single grapevine for each replication. Two different concentrations (10 mg·L– 150 mg·L– 1) of prohydrojasmonmethyl jasmonate were respectively applied to theChristmas Rosegrape berries. The aqueous solutions of both treatments and control involved 0.1% Tween-80 and 1% ethanol. The experimental grape berries were sprayed uniformly with aqueous solution twice at the beginning of veraison and 7 days later after the first application. After the first treatmentsamples were taken every 10 days until the fruit was ripe when the seeds were completely brown and the soluble solids content no longer increased. A total of 40 single berries from the topmiddle and bottom parts of randomly selected 10 grape bunches were picked and brought to the laboratory for analysis. The coloration of the grape berry was measured by a Minolta colorimeter and expressed as the value (the fruit surface light brightness) value (color component of red and green) value (color component of yellow and blue) and CIRG value (color index of red grape). Anthocyanin content in the skin extraction was measured by the pH differential method. The contents of chlorophyll a and chlorophyll b in the skin extraction were tested according to the Arnons method. The soluble solids content of the fruit was measured by a PR-101 refractometer. The titratable acid in the grape juice was titrated by 0.1 mol·L– 1 NaOH according to the Gaos method. The total phenolicsand flavonoids in the skin extraction were determined respectively according to the Jia and Meyers method. The pedicel endurable pulling force and berry endurable pressing force were measured by a Digital Push & Pull Tester. In additionthe berry weightberry lengthberry diameterand the content of vitamin C were also determined. All analyses were performed using Excel and SPSS software.

Results:

During the ripening period of the grapes that were treated or not treatedthe L valueand b value decreasedwhile the a valueand CIRG value increasedthe brightness of the grape skin declined and the coloration of the grape skin was transformed from green to red. The grape berries treated with PDJand MeJA had a higher valueCIRG value and a lower value value than the control. The highest valueCIRG value and the lowest value value were found in the grapes treated with 50 mg·L-1 PDJ. At harvestthe CIRG value of 50 mg·L-1 PDJ-MeJA- treated grapes reached 4.61 and 4.50 respectively while the CIRG value of the untreated grapes was only 4.04. During the ripening period of the grapesthe anthocyanin content rose graduallyin contrast to chlorophyll a and chlorophyll b which declined gradually in the grape skin. The content of anthocyanin in the grape skin treated with PDJand MeJA was obviously higher than the control. The 50 mg·L-1 PDJand MeJA treated grapes presented a higher an⁃ thocyanin content than the 10 mg·L-1 PDJand MeJA- treated grapes. The PDJ treatment had a better effect than the MeJA treatment under the same concentration on increasing the content of anthocyanin. At harvestthe anthocyanin content in the grape skin treated with 50 mg·L-1 PDJand 50 mg·L-1 MeJA was respectively 31.2%and 20.0% higher than the control. The content of chlorophyll a and chlorophyll b in the grape skins treated with PDJand MeJA were lower compared with the control. The PDJand MeJA treatments promoted the synthesis of anthocyanin while enhanced the degradation of chlorophyll a and chlorophyll band the coloration of the grape berry improved. The 50 mg·L– 1 PDJ treatment performed best in improving the coloration of the grape berries among all of the treatments. During the period of maturationthe soluble solids content of grapes treated with PDJand MeJA were obviously higher compared with the grapes that were untreated. The 50 mg·L-1 PDJand MeJA treatments were more effective in increasing the content of soluble solids than the 10 mg·L-1 PDJand MeJA treatments. There were no obvious differences between the treated and untreated grapes on the titratable acid content. The application of PDJand MeJA promoted the accumulation of total phenolicsand flavonoids in the skin at harvestand total phenolics in the skin treated with 50 mg·L-1 PDJand MeJA were respectively 36.4%and 29.0% higher than the control. The application of PDJand MeJA significantly enhanced the content of vitamin C in the fruithoweverthe berry weightberry length and berry diameter were not influenced. The grape treated with PDJand MeJA had a higher nutritional qualityin additionthe PDJand MeJA treatment did not have a negative effect on fruit yield. The pedicel endurable pulling force and berry endurable pressing force were not influenced by the PDJand MeJA treatment. The phenomenon of berry drop did not happen in the treated grapes. There was no difference between the treated and untreated grapes on resistance to storage and transportation.

Conclusion:

Two different concentrations of exogenous PDJand MeJA improved coloration and quality of theChristmas Rosegrape berry compared with the control. Under the same concentrationthe PDJ treatment had a better effect than the MeJA treatment on improving coloration and the quality of grapes; the 50 mg·L-1 PDJand MeJA treatment showed a better effect than the 10 mg·L-1 PDJand MeJA treatment. Among all of the treatmentsthe 50 mg·L-1 PDJ treatment was the most effective in improving the coloration and quality of grapes in the trial.

By  SUN XiaowenGAO DengtaoWEI ZhifengGUO Jingnan*CAO Meng
Zhengzhou Fruit Research InstituteCAASZhengzhou 450009HenanChina

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