Effect of bagging on fruit pigmentation in two types of red-fleshed kiwifruit

【Objective】The study explored the effect of bagging on fruit pigmentation in two different types of red-fleshed kiwifruit in order to provide evidence for the impacts of illumination on anthocyanin synthesis.【Methods】Two different types of red-fleshed kiwifruit‘Hongyang'and‘Tianyuanhong'were selected as materials for bagging treatments. Color parameters at different parts of fruit collected at different times were measured with a Konica Minolta portable color meter CR-400. These parameters included L value representing light intensity, a value, the indicator of redness and greenness, b value, the yellowblue indicator, h value, the color ratio, and h*value, the hue angle. High-performance liquid chromatography(HPLC) was also used for semi-quantitative analysis of pigments in fruit from different treatments.【Results】The a values in different treatments and different parts of‘Hongyang'fruit displayed a rising trend while b values were always positive and tended to increased from 30 days after full bloom(DAFB) to50 DAFB. The h and a values had a consistent change pattern, and the hue angle of the outer pericarp and the inner pericarp of‘Hongyang'was significantly decreased by bagging treatments, which promoted the degreening of the outer pericarp and the reddening of the inner pericarp. The a, b and h values and hue angle were significantly different between different parts. The a value of the inner pericarp in different treatments and different stages had no significant difference after 70 DAFB. The b value of the inner pericarp in different treatments had no significant difference, while it was significantly different among different stages. The h value of the inner pericarp in different treatments and different stages had significant difference after 70 DAFB. The hue angle of the inner pericarp in different treatments had no significant difference, but was significantly different among stages. Anthocyanins could not be detected in the outer pericarp of‘Hongyang'throughout fruit development. However, anthocyanins in the inner pericarp were detectable from 70 DAFB, and then anthocyanin content displayed an alternative increase trend. The peak value of anthocyanin content in the inner pericarp in different treatments was different. The anthocyanin content in bagging treatment and bagging-debagging treatment peaked at 80 DAFB, while non-bagging treatment peaked at 120 DAFB. At the early stage of‘Hongyang'fruit development, and at 70 DAFB, 80 DAFB, and 90 DAFB, the anthocyanin content in the inner pericarp of bagging-debagging treated fruit was higher than that in the bagging treatment and non-bagging treatment fruit. The anthocyanin content of the inner pericarp in non-bagging treatment increased from 100 DAFB to120 DAFB and reached its maximum value at 120 DAFB, which was higher than that in bagging treatment and bagging-debagging treatment. The anthocyanin content was significantly different between different treatments, fruit parts and stages. The a and b values in different treatments and different parts of‘Tianyuanhong'had irregular change pattern during the fruit development. The h and a values changed following a consistent pattern,the latter having a higher variation range. The hue angle of the three parts in the three treatments decreased from 90 DAFB to 100 DAFB, which might be a key stage of color transformation. The hue angle of the outer pericarp of bagged fruit at different stages was lower than that of the non-bagged fruit and of the fruit with bagging-debagging treatment, indicating that bagging treatment could promoted the pigmentation of the outer pericarp. The bagging treatment could dramatically decrease the hue angle of the epicarp of‘Tianyuanhong', while it had a less effect on sarcocarp and columella. The results showed that h value and hue angle had significant difference between different treatments, different parts and different stages.Bagging could hinder the accumulation of anthocyanins in the epicarp, outer pericarp, inner pericarp(sarcocarp) and columella. The anthocyanin content in the epicarp and sarcocarp in the bagging-debagging treatment increased significantly, and reached a peak value at 110 DAFB, when the anthocyanin content in the epicarp and sarcocarp of debagged fruit was significantly higher than that of the non-bagged and bagged fruits, while the anthocyanin content in the columella was not. The difference in anthocyanin content in different treatments, different fruit parts and different stages reached significant levels.【Conclusion】Debagging treatment could dramatically increase the anthocyanin content in the inner pericarp of‘Hongyang', compared with the non-bagged fruit, and promote the coloration of the inner pericarp. Bagging treatment mainly influenced the outer pericarp and had less effect on the columella. Bagging could also promote the coloration of inner pericarp, but its effect was not as prominent as the bagging-debagging treatment. Bagging-debagging treatment could also dramatically increase the anthocyanin content in the epicarp and sarcocarp of‘Tianyuanhong'and promote the coloration of the epicarp and sarcocarp. Bagging hindered the accumulation of anthocyanin of‘Tianyuanhong'fruit and had an effect on fruit color.