Document Type : Full Paper
Authors
1 Horticulture Crops Research Department, Mazandaran Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Sari, Iran.
2 Soil and Water Department, Mazandaran Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Sari, Iran
3 Citrus and Subtropical Fruits Research Center, Horticultural Science Research Institute, Agricultural Research Education and Extension Organization (AREEO), Ramsar, Iran
Abstract
Keywords
Main Subjects
Extended Abstract
Introduction
The citrus cultivation area in Mazandaran province, north of Iran, is about 120000 ha with about 3 million tons of annual production. Thomson navel variety acconuts for about 70 percent of Mazandaran’s orange production. The use of different cultivars, in addition to satisfying the tastes of different consumers, allows producers to have enough time to sell their products. Sour orange has been used as a commercial citrus rootstock in Iran and the world, but in recent years, the use of it has been limited due to the high sensitivity to citrus Tristeza virus and also to soil flooding. Therefore, to maintain the stability of the citrus industry and to deal with a variety of biotic and abiotic stresses (especially due to changes in climatic conditions), it is necessary to use various cultivars and rootstocks and examine them in the conditions of a certain region.
Materials and methods
In order to investigate the vegetative growth of some recently introduced navel orange ('Fucumoto' ; 'Navelina'; 'Navelate'; 'Thomson navel'; 'Cara cara' and 'Lane late navel'), grafted on three poncirus hybrids rootstocks ('Carrizo citrange'; 'Swingle citrumelo' and 'C-35 citrange'), a factorial experiment in a randomized complete block design was conducted during 2014-2020 in the eastern region of Mazandaran. Plant responses included traits related to vegetative growth such as tree volume, rootstock and scion morphological compatibility, leaf nutrient concentration and tree survival were examined.
Results and discussion
All measured vegetative traits, including height, canopy width, tree volume, rootstock perimeter, cultivar perimeter and morphological compatibility were affected by year, rootstock and cultivar. The rootstock type affected the concentration of all nutrients in the leaves. Tree height and volume, and the required area for orange trees grafted on the 'citrange' were less than the other two rootstocks. 'Navelate' and 'Lane late navel' cultivars had the highest and 'Fukumoto' had the lowest tree volume. The morphological compatibility (affinity) of the graft union decreased with the increasing age of the trees. In the last year, there was the lowest compatibility between 'Fukumoto' cultivar and 'citrumelo' rootstock (0.60) and the highest between 'Navelate' cultivar and 'Carrizo citrange' rootstock (0.77). Some trees of 'Fukumoto' and 'Navelina' with 'C-35' rootstock had signs of blistering in the peel of the rootstock and scion at the grafting site in 2019. In 2020, some of them showed symptoms of leaf yellowing. These trees had signs of root rot. In 2021, one of the 'Fukumoto' and one 'Navelina' tree on the 'C-35' rootstock had severe defoliation and death of the top branches and were completely declined. Other rootstocks and cultivars did not show any signs of yellowing. The maximum area required for seven-year-old trees of these 18 combinations with regular annual pruning was about 9.5 m2, which was recorded in 'Navelate' cultivar on 'C-35 citrange' rootstock.
Conclusion
For optimal land use, tree planting distance should be considered based on the expected volume of the mature tree on the selected rootstock in the soil and climate of the region. Result of this research showed that the plant density based on the height and width of the canopy of different varieties of early, mid and late-ripening navel oranges on different rootstocks, along with annual pruning, could be increased to more than 800 trees per hectare, which is much higher than the common planting density in the region. For 'Fukumoto' and 'Navelina' cultivars, the use of 'C-35' rootstock is not recommended due to the possibility of incompatibility between the rootstock and the scion.
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