Postharvest physiology
Fatemeh Ahmadi; Mohammad Mehdi Sharifani; Amir Mousavi; Negin Akhlaghi Amiri; Mostafa Khoshhal Sarmast; Khalil Zaynali Nezhad
Abstract
IntroductionExternal and internal quality of citrus such as color, shape and taste increase economic benefit. The vigour of each rootstock causes qualitative and quantitative change and the effective factor on commercial maturity, which is important for gardeners and producers. Considering the characteristics ...
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IntroductionExternal and internal quality of citrus such as color, shape and taste increase economic benefit. The vigour of each rootstock causes qualitative and quantitative change and the effective factor on commercial maturity, which is important for gardeners and producers. Considering the characteristics of the fruit in grafted trees, the present research was conducted with the aim of evaluating the effects of trifoliate orange, Citrange and Citrumelo rootstocks on some morphological, phytochemical and molecular traits of ‘Thomson Navel’ orange fruit. Materials and MethodsThis research was carried out in 2018 at Ghaemshahr Horticultural Research Station, Mazandaran. It was conducted in the form of randomized complete block design (RCBD) of uniform and 10-year-old ‘Thomson Navel’ orange grafted on ‘trifoliate orange’, ‘Citrange’ and ‘Citrumelo’ rootstocks with four replications. The samples were collected at the end of October and were transferred to the research laboratory of Horticulture Department, Gorgan University of Agricultural Sciences and Natural Resources for further research. Measurements were made on the morphological traits, quality characteristics of the fruit, the phenolic compounds of the peel and the pulp of the fruit and relative expression of fruit pulp sucrose phosphate synthase1 gene. Data variance analysis was done using SAS software (version 9.0). Mean comparisons were done with Duncan's multiple range test. Results and DiscussionThe results of analysis of variance showed that the rootstock effect on traits of length-to-diameter ratio, weight and density of ‘Thomson Navel’orange was significant at the five percent probability level (p<0.05) and the fruit length and diameter traits were significant at the one percent probability level (p<0.01). The results of mean comparison showed that the characteristics of length, diameter, length-to-diameter ratio, weight and density of ‘Thomson Navel’ orange at commercial maturity on the trifoliate orange rootstock were more than the two other rootstocks. Due to the early harvest, the density of the fruit was recorded lower than one, so that the highest amount (0.5 g per cm3) was observed in the rootstock of trifoliate orange however it was not significantly different from Citrange rootstock. Based on the results of analysis of variance, it showed that the effect of rootstock on total soluble solids was significant at the level of five percent. Also, the rootstock had a significant effect on titratable acidity, taste index, vitamin C, acidity, EC and total sugar at the level of one percent. However, the amount of vitamin C was higher in the Citrumelo rootstock. The highest amount of acidity and EC belonged to trifoliate orange rootstock and the lowest amount belonged to Citrange rootstock. The highest amount of total sugar was observed in the dwarfing trifoliate orange rootstock, while its lowest amount was recorded in the vigorous Citrumelo rootstock. The highest amount of total soluble solids was observed at the rootstock of the trifoliate orange. The amount of titratable acid in the Citrange rootstock was higher than the other two rootstocks. The taste index was higher in the trifoliate orange rootstock than the other rootstocks. According to the results of analysis of variance, the rootstock effect on the index of total phenol of fruit peel and pulp and total flavonoid of fruit peel was significant at the five percent probability level (p<0.05) and only on the antioxidant activity of the fruit peel at the statistical level of one percent (p<0.01). Also, there was no significant difference in total flavonoid traits and antioxidant capacity of fruit pulp. The highest amount of total phenolic, total flavonoid and percentage of antioxidant activity was found in the trifoliate orange rootstock. Also, between the fruit organs, phenolic compounds were recorded more in the fruit peel compare to the fruit pulp. The peel of orange is more exposed to ultraviolet rays and changes in environmental conditions, Therefore more secondary metabolites accumulate in that part of the plant. The highest relative expression of fruit pulp sucrose phosphate synthase1 gene was obtained in the Citrange rootstock. ConclusionThe vigor of different citrus rootstocks caused the dwarf trees to have a higher accumulation rate of phytochemical indices than the vigorous trees. The trifoliate orange rootstock is suitable for fresh consumption due to the early commercial maturity of the fruit. Fruit peel rich in phenolic compounds is used for medicinal purposes. The technical knowledge from this research will be useful for citrus producers in East Mazandaran.
