A study of the characteristics of browning in bagged Ruixue apple fruit and its relationship to temperature

Abstract:【Objective】In order to explore the effect of temperature factors on browning during fruit de-velopment in Ruixue apple, the article studied the relationship of pericarp browning of bagged Ruixue apple (Malus domestica Borkh.‘Ruixue’) with temperature.【Methods】Five- year- old Ruixue trees were used as the experimental material and M26 as rootstock. The study investigated the fruit browning rate 90, 120, 150, 160, 170, 180, 190 and 200 days after full bloom. Temperatures in the fruit bag and in the air during fruit development were recorded. The relationship of the temperature difference between the air and the fruit bags and the browning rate was analyzed.【Results】The results showed that with the extension of bagging time, the browning rate of the pericarp of Ruixue apple became higher. 200 days after full bloom, the browning rate of G bag reached 85.56% and the browning rate in bagging treatment with a special bag type reached 70%. Fruit in G fruit bags started to appear symptoms 150 days after full bloom, while those in the special fruit bags begun to appear the symptoms of browning 160 days after full bloom. The browning rate of fruit in G fruit bags was higher than those in special fruit bags. From 150 to 200 days after full bloom, the browning rate in G fruit bags was 4.44% to 24.44% higher than that in special fruit bags. The daily average temperature (Tmean), daily maximum tem-perature (Tmax), daily the difference of day and night temperature (TD), effective accumulated tempera-ture (GDD), accumulated daily maximum temperature (STmax), and accumulated daily the difference of day and night temperature (STD) in the fruit bags were lower than in the air. Daily minimum tempera- ture (Tmin) and accumulated daily minimum temperature (STmin) had no difference between the fruit bags and the air. From 150 to 200 days after full bloom, GDD in the special fruit bag was 24.0 ℃ to 72.0 ℃ lower than in the air, and STD was 140.2 ℃ to 330.3 ℃ lower than in the air. GDD in G fruit bag was 62.0 ℃ to 126.7 ℃ lower, and STD 224.2 ℃ to 467.6 ℃ lower than in the air. The accumulated rate of GDD, STmax and STD in the air were higher than in the fruit bags, while the accumulated rate of STmin in the air was lower. The accumulation rate of GDD in the air, special fruit bag and G fruit bag was 3.64, 2.66 and 2.34 ℃·d-1, the accumulation rate of STmax 23.02, 19.82 and 18.54 ℃·d -1, the accumula-tion rate of STD 16.17, 12.30 and 11.22 ℃ · d^-1, and the accumulation rate of STmin 6.85, 7.52, and 7.32 ℃·d -1, respectively. From 150 to 200 days after full bloom, the temperature factors inside the fruit bags were quite different from those in the air. The △GDD of the G fruit bags was 38.00 ℃ to 54.72 ℃ lower than in the special fruit bags. △STmax in G fruit bag was 98.60 ℃ to 161.50 ℃ lower than in the special fruit bags. The △STD in G fruit bag was 84.00 ℃ to 137.30 ℃ lower, and △STmin 14.60 ℃ to 24.20 ℃ lower than in the special fruit bags. │△GDD│, │△STmax│, │△STmin│ and │△STD│had a significant correlation with │△PB│, of which │△GDD│ and │△STD│ had the greatest correlation. In the special fruit bag, the correlation coefficients were 0.881 and 0.88, respectively, while in the G fruit bag, the correlation coefficients were 0.947 and 0.943, respectively, and there was a non- linear regression relationship among │△GDD│, │△STD│ and │△PB│. The big differences in GDD and STD between the inside and outside of the fruit bags were the key factor in the occurrence of peel browning in Ruixue.【Conclusion】The temperature factors inside and outside the bags were quite different in the later stage of fruit development, therefore peel browning in the bagged Ruixue apple was caused by the temperature conditions in the later stage. According to the correlation analysis, the browning of the bagged Ruixue apple was closely related to the lower effective accumulated tempera- ture and the lower accumulation of diurnal temperature difference in the fruit bags.