Effect of Harvest Date on Yield and Storability of Washington Navel and Valencia Orange Fruits Under on-Tree and Cold Storage Conditions

Abstract

This study was conducted during two successive seasons of 2013/2014 and 2014/ 2015 on 15-year-old Washington navel and Valencia orange [Citrus sinensis (L.) Osbeck] trees grafted on sour orange rootstock. The experimental trees were grown in clay loam soil of a private citrus orchard located at Menia El-Kamh district, Sharkia Governorate, Egypt. Fruits were harvested at 5 successive monthly intervals on the first of each of Dec., Jan., Feb., Mar. and Apr. for Washington navel orange. Valencia orange fruits were harvested one month later at five periods beginning with first Jan. and ending with first May. On each harvest date fruits of three trees (3 replicates) were harvested, counted and weighed. About 60 healthy undamaged fruits from each replicate were randomly selected for cold storage at 7ºC±1 and 85-90% RH. Fruit samples selected at harvest day (15 fruits) and those taken at 30 days intervals from cold stored fruits were subjected to determine the effect of on-tree, cold storage and harvest date on physicochemical fruit characteristics. Washington navel orange gained the highest fruit weight, TSS/acid ratio, fruit weight loss and fruit decay percentages, whereas, Valencia orange produced higher fruit yields with higher vit. C content. Yield/ tree, fruit weight, TSS/ acid ratio and vit. C content were markedly decreased by delaying fruit harvest (on-trees fruits storage) and increasing storage period, but weight loss and decay percentages were increased. All possible interactions between the three tested factors were significant in the two seasons, and confirm the previously recorded trends of each individual factor on the tested physicochemical fruit characteristics. The obtained results revealed that the storability of Valencia orange fruits was clearly better than that of Washington navel orange fruits, since weight loss and decay percentages of the later orange variety were about 2 and 15 folds than that of Valencia orange fruit, respectively (average of both seasons).