Document Type : Full Paper
Extended Abstract
Introduction
Iran, with 288 thousand hectares of citrus-cultivated area, 5.5 million tons annual production and a yield of 20 tons per hectare, in 2022 ranks sixth, seventh, and fifth in the world, respectively. Mazandaran Province (the most important region for citrus production in Iran) supplies close to 70 percent of the country's oranges, more than 70 percent of which are the ‘Thomson navel’ variety on sour orange rootstock. Therefore, it is very important to evaluate new cultivars and suitable rootstocks to replace them, if necessary. In the present study, the effects of ‘Swingle’ citrumelo, ‘Carrizo’ citrange and ‘C-35’ citrange rootstocks on vegetative growth, quantitative and qualitative yield, and harvest time of the ‘Cara Cara’ navel orange were investigated in the eastern region of Mazandaran over seven years.
Materials and Methods
This research was performed in a completely randomized block design using ‘Cara Cara’ sweet orange as scion cultivar on three rootstocks, with six replications and a 5 × 3 m planting distance during 2013-2020. After planting in the main field, the young trees were trained for four years and then pruned annually in winter. Plant responses included tree volume, rootstock and scion morphological compatibility (affinity), amount and efficiency of yield, fruit characteristics at different times, appropriate time for harvesting, and theoretical space requirements of the trees for better land utilization.
Results and Discussion
According to the results of the seven-year trials, ‘Cara Cara’ orange revealed pink flesh and orange peel on all rootstocks. The trees showed alternate bearing cycles in different years. This variety showed the highest tree volume and yield on ‘Swingle’ citrumelo rootstock and the highest yield efficiency on ‘Carrizo’ citrange rootstock. Taking into account the quantitative and qualitative indicators of the fruits, the appropriate time to start harvesting ‘Cara Cara’ oranges in the east of Mazandaran is the third week of November, when the average harvest index is 7.8, fruit weight is 280 g, peel thickness is 3.5 mm, the amount of fruit extract is about 44%, and the color of the peel is pale orange. The process of increasing the harvest index and fruit weight and changing peel color continues until mid-December. A delay in harvesting causes an increase in rotting and fruit drop before harvesting, a decrease in tree reserves, and as a result, a decrease in flowering and yield in the next year, as well as an increase in the sensitivity of the fruit and tree to the occurrence of cold and possible frosts.
Conclusion
In the present study, after seven years of planting in the main field, based on the height and diameter of the trees and considering 2.5 meters of empty space between the rows of trees, the theoretical space required by the most vigorous rootstock, ‘Swingle’ citrumelo, was 7.3 m2 in the seventh year, which, if the slow increase in width and volume of the trees in the following years is also considered, the space required for planting ‘Cara Cara’ trees would be much less than the usual spacing for planting an orchard in Mazandaran province. By training and pruning young trees and annual winter pruning, semi-dense planting with 3 × 4 m spacing and even less is possible to make better use of the land in this region..
Author Contributions
All authors contributed equally to the development of this manuscript from the initial draft to the final submitted version, including all subsequent revisions.
Data Availability Statement
Data available on request from the authors.
Acknowledgements
This research was supported by grants from Horticultural Science Research Institute (HSRI) Projects No. 2-17-17-92102 and No. 0-60-33-043-970369
Ethical considerations
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
Conflict of interest
The author declares no conflict of interest.
