The Effect of Rootstock and Foliar Application of Calcium chloride, Calcium nitrate and Boron Mixture on some Qualitative and Quantitative Traits of "Starking" Apple Cultivar

Apple tree is one of the widely grown fruit crops in Iran. Apple is not only consumed as fresh fruit in Iran but also it is one of the most important export products in country. Iran has a good ranking among the first world ten apple producing countries and it annual production is about three million tons. Although Iran has acceptable ranking in the case of apple production in the world, but its mean yield is about 13 tons per hectare. Unsuited nourishing and unbalancing of the nutrients in the soils is one of the reasons for reducing of apple yields in most parts of Iran. Calcium (Ca) is one of the plant nutrients that most closely related to improvement of fruit quality and increasing of fruits shelf life. Calcium mobilization from leaf to fruit is controlling by transpiration of plant. With growing of fruits, calcium deficiency will be increase especially in high temperature and drought condition because of dilution effect. Calcium ions bind tightly to the pectins in the cell walls and produce cationic bridges between pectic acids, or between pectic acids and other acidic polysaccharides. These bridges make the cell walls less accessible to the action of pectolytic enzymes. It is suggested that addition of calcium to fruit can either enhance resistance of fruit to postharvest pathogens or reduce susceptibility to postharvest diseases and disorders. Calcium chloride (Ca Cl2) and calcium nitrate [Ca (NO3)2] are commonly used for foliar sprays. Application of calcium chloride has been reported to control fruit disorders and improve fruit quality of apples and pears. Calcium chloride solution by immersion did not significantly differ from the untreated control in pH, total soluble solids (TSS), total titratable acidity (TA). Boron is an essential micronutrient required for optimal yield and quality of apple fruit. Its availability to plants decreases with increasing of soil pH and under drought condition. Boron deficiencies may reduce Ca movement in a tree. Boron plays a significant role in pollination success and it plays a role in the trees ability to translocation of Ca from the roots to other parts of the tree. Foliar application of boron is preferred over soil application because of the very narrow range from deficient to toxic levels. Efficiency of calcium and boron increases plant height by increasing mitotic activity in the terminal meristems. Dwarfing rootstocks have been used in most parts of the world. They have more differences in adaptability with different soils and agro-climatologically conditions. Recently using from East Maling 9 (M9) and Maling Merton 106 (MM106) has been extended in Iranian apple gardens. Regarding to the difficulties of apple growing gardens in Iran that due to appearing serious difficulties in nutrients absorption by plants and importance of improvement of qualitative and quantitative apple production on the other hand, this study carried out.

The research study was conducted at the Khorramdarreh region located in 36○ .13' eastern longitude and 49○ .12' northern altitude and 1560 meter above the free seas levels, during spring and summer 2014 to determine the influence of foliar calcium chloride + calcium nitrate and boron mixture application on growth and yield performance of Star King apple cultivar grafted on M 9 and MM 106 rootstocks. Trees were nine years old. The experiment was laid out in factorial based on randomized complete blocks design with 3 replications. Factor A was rootstock in two level(M 9 and MM 106) and factor B was foliar spraying of calcium chloride + calcium nitrate and boron mixture with three levels(0, 3000 and 5000 ppm). Mixture of calcium chloride, calcium nitrate and borax (3000 and 5000 ppm), were applied as foliar spray in four times with 22 days interval started from 28 of June (after June drop). A back-held spray pump was used for foliar application of the chemicals. After spraying two branches were selected at two eastern and western directions with 80-100 centimeter length and 1-1.5 centimeter diameter for noting the growing related traits such as length and diameter of new branches also the tress height and diameter were noted. After ripening of the fruits, ten randomly selected fruit were picked around the tree canopy from each treatment and in laboratory some qualitative characteristics such as pH, titrable acid and total soluble solids of them were tested. The data were analyzed using MSTAT-C software and treatment means were separated by the Duncans Multiple Range Test (DMRT) at a 0.05% level of significance.

Results showed that effect of rootstock factor was significant on length of new branches, tree diameter, annual increasing of tree diameter and fruit pH. The highest length of new branches (30.56 cm) belonged to MM 106 rootstock that 47% increased comparing with M9 new branches length. The lowest tree diameter was 11.50 cm and belonged to M 9 rootstock that decreased about 51% comparing with MM 106 rootstock. The highest annual increasing of tree diameter (6.8 mm) belonged to MM 106. The maximum fruit pH (4.7) belonged to M9 rootstock that had significantly differences with fruit pH in MM 106(4.5).Concentration factor had significantly effect on individual tree fruit yield, yields per hectare, length and diameter of new branches, trees height and diameter, annual increasing of tree diameter, fruit total soluble solid, fruit juice and fruits texture hardiness. Interaction effect of rootstock × concentration was significant only on length of new branches. With increasing of solution mixture (calcium chloride + calcium nitrate and boron) concentration, growing of new branches (in length and diameter), trees height and diameter were increased.

It can be concluded from these results that three time foliar application of calcium chloride + calcium nitrate and boron mixture on Star King apple cultivar grafted on M 9 and MM 106, results in a significant increase in tree and fruit qualitative and quantitative production. According to the results of study spraying of Star King apple cultivar with 5000 ppm concentration of calcium chloride + calcium nitrate and boron mixture, recommended in Khorramdarreh region.