Influence of Rootstock and Variety on Leaf Nutrient Concentration of Pear Grown on a Nutrient-Sufficient Soil

Study was aimed to investigate the effect of rootstock, variety and their combination on mineral nutrition of pear. For this reason, Deveci, Santa Maria and Akca varieties grafted on Quince A, Quince C, BA 29 and OHF 333 rootstocks were used as plant materials. To compare nutritional status of plants, N, P, K, Ca, Mg, Fe, Cu, Mn Zn and B analysis were made on leaf samples. According to results, it was seen that individual effect of rootstock and variety and their combinations had significant effect on pear mineral nutrition generally. Although there was a significant variation depending on rootstock and variety differences, we could not reach a certain result which rootstock and variety or their combinations were prominent on general mineral nutrient concentration of pear. We assumed that this was due to preventing of the effectiveness of rootstock or variety because of sufficient nutrient levels in the soil. Research Article Article History Received : 13.05.2019 Accepted : 27.06.2019


INTRODUCTION
There are many factors effecting plant nutrition and nutritional status of a plant. These factors can be classified under three main groups such as soil, environment and plant factors. Soil texture, depth, pH, salinity, cation exchange capacity, CaCO3, organic matter, available nutrient concentrations and balance are some of the soil factors. Also, precipitation and its characteristics, humidity, temperature, lighting period etc. play roles on soil fertility and plant nutrition. Besides above factors, plant factors are the main criterion on determining the degree of impact of these factors. For instance, plant type and variety, age of plant, growth stage, root structure and other genotypic properties plays different roles on nutrient uptake ability of a plant (Erdal et al., 2008;Marschner, 2012). Nutrient uptake capacity of a plant varies from plant to plant even they are different genotypes of a plant type (Clark and Gross, 1986). These variations can be seen even they are grown on the same soil and the same conditions (Marschner, 2012 Kucukyumuk andErdal 2011;Kucukyumuk et al. 2015). In horticultural production, rootstock and variety are the main two important factors influencing the performance and survival of a cultivar against un-favorable conditions. So, choosing proper rootstocks and variety is important for a successful orchard establishment. In order to get better plant growth and quality yield, nutrient removal and transport capacity of plant cultivars and their rootstocks should be considered (Tsipouridis et al., 1990;Kucukyumuk and Erdal 2011). In different studies, it was well documented that there were close relations among rootstock, variety and plant nutrition. Studies conducted by Fazio et al., (2015), Nava et al., (2018)  Turkey is among the most pear producing countries, but export is not satisfactory (FAO, 2018). Although, there might be several reasons for this, the most reasonable reason is fruit quality due to non-suitable rootstock and variety chose. Suitable rootstock and variety can improve yield amount and yield quality with different ways. For example, resistance to environmental effects such as pest and disease, drought, salinity, frost, nutrient deficiency etc. can vary between rootstocks and scions (Westwood, 1995;Hartman et al., 1997;Fazio et al., 2015;Mestre et al., 2017).
In this study, it was aimed to investigate the effect of rootstock and variety and their combinations on mineral nutrition of pear plant under nutrientsufficient soil condition.

Plant Materials
The study was carried out on Deveci, Santa Maria and Akça varieties grafted on Quince A (QA), Quince C (QC), BA 29 and OHF 333 rootstocks. Some characteristics of varieties and rootstocks are given below (Fig 1).

Varieties
Deveci: It is an Anatolia originated medium strength and semi-splayed, late season pear variety. It has large-very large fruit. The lower part is wide and flattened. Fruit peel is rough, ground color is yellow. The time between full flowering and harvesting is 150-160 days. It is very sensitive to fever blight (Fig 1 a).
Santa Maria: Italia originated mid-season pear variety. Tree has medium strong, growth is perpendicular. Fruit is semi-large, the neck is long, and expands through down. The time between full flowering and harvesting is 115-125 days (Fig 1b).
Akca: Anatolia originated early season pear variety. Tree is strong, growth is semi-perpendicular. Fruit is small with short neck and expands through down. The time between full flowering and harvesting is 75-85 days (Fig 1c).

Rootstocks
Quince C (QC): It is a quince originated rootstock. It forms a weaker canopy than Quince A. It is sensitive to fire blight and soil lime content.
Quince A (QA): It has a medium vigor and forms a canopy of about 50% of the seedling. It has a shallow rooting system. It is sensitive to fire light and soil lime content.
BA 29: It forms a canopy of about 60 % of seedling. Compatibility with pear varieties is better than Quince A and Quince C rootstocks. It is sensitive to chloroses, drought and cold, but tolerant to nematode.

Experiment Set up
The experiment was carried out in a split-plot design having 4 replications on 13 years old pear trees and each replication had 4 trees. As fertilization, 30 kg ha -1 N, 15 kg ha -1 P, 10 kg ha -1 K were applied from ammonium nitrate, mono ammonium phosphate and potassium nitrate.

Leaf Analysis
Leaf samples were taken from the four sides of trees after 8-10 weeks after full blooming. Samples were washed with dilute acid, top water and pure water. Then, dried, grinded and digested for mineral analysis. Nitrogen was measured according to modified Kjeldahl method (Bremner 1965). Other nutrients (P, K, Ca, Mg, Fe, Cu, Mn, Zn and B) were determined using ICP-OES (Spectro Arcos FHM 22) as described by Jones et al., (1991) Statistical Evaluation Data were analyzed with MSTAT-C program and differences between the means were separated by Duncan's Multiple Range Test (P ≤ 0.05).

Rootstock and Variety Effect on Macronutrient Concentration of Pear
Leaf N, P, K, Ca and Mg concentrations of pear plants have been seen in Table 1. As indicated there, rootstock and variety difference had a significant effect on leaf N concentrations. While OHF 333 and QA rootstocks showed variation in terms of leaf N concentrations others took part in the same statistical classification. Deveci and Santa Maria cultivars contained the same amount of N and these concentrations were found to be significantly higher than Akca cultivar. Leaf P concentrations showed significant variation depending on Rootstock x variety interaction. Although leaf P concentrations varied between 0.193 % (QA x Akca) and 0.278 % (QC x Akca) with interactions, only the differences between QC x Akca -QA x Akca and OHF 333 x Deveci were significant. Differences among the other variations were not significant. Leaf K concentrations have been affected from interactions of rootstock and variety. When looked at the results, it can be seen that there were quite differences among the interactions. The lowest K levels were measured on the leaves of QA  *Capital letters shows the differences between the means of main factors (rootstocks and varieties) **: Small letters shows the interaction effects.
Similar variable findings were observed on the varieties as well. Differences in leaf nutrient concentration among the varieties and rootstocks are can be attributed to the inherent capacity of the varieties and rootstocks to take nutrients and their translocation in the plants (Meland, 2010;Fazio et al., 2015;Mestre et al., 2015). Previous studies indicated that plant can take different amount of nutrients even they are grown in the same conditions (Clark and Gross, 1986;Erdal et. al., 2008;Kucukyumuk and Erdal 2011;Erdem and Ozturk, 2012;Ikinci et al., 2014). Also, structure of root system, it's density, surface area, cation exchange capacities etc. influence plant's nutrient absorbing capacity (Marschner, 2012). Variations of root exudates and their properties depending on the rootstocks might play a role on nutrients availability to plants by means of rhizosphere acidification and chelating properties (Rengel 2001;Dakora and Phillips, 2002;Marschner, 2012). There might be other reasons for these variations. For example, resistance of a rootstock or variety against to abiotic or biotic stresses can be an advantage of a plant to receive more nutrients from the soils (Rengel 2001;Fazio et al., 2015). One of the other nutrient concentration variations can be the differences in plant size of varieties. As indicated before, nutrient demand and uptake generally increase with plant size and it's biomass (Mugasha et al., 2013;Peng et al., 2019). At the same time, physiological need of varieties had an important effect on nutrient requirement.
Although there were significant variations between rootstocks and variety and their combinations for some nutrient concentrations in the leaves, we could not see prominent rootstock or variety or their combination on pear nutrient concentration. This may be due to nutrient supplying capacity of the experiment orchard's soil. Nutrient concentrations were sufficient generally (Keren and Bingham 1985;Alpaslan et al. 2005) and about all nutrient concentrations in the leaves were between the sufficiency levels (Jones et al., 1991). This may have blocked the effectiveness of rootstock x variety combinations on specific nutrient uptake capacity. Similarities and proximities of the rootstocks in terms of plant size may be the other factor.
It can be concluded that it is better to work with nutrient deficient soils to reach certain results on which rootstock and variety or their combinations effective on plant's mineral nutrition. And the results should be revealed with the findings of other probable factors effecting plant's nutrient concentrations.