Growth , yield and fruit quality of ‘ Chimarrita ’ peach trees grafted on different rootstocks

Rootstocks influence the performance and characteristics of fruit trees. However, there is still insufficient information on the relation of rootstocks in mainly cultivars of peach trees grown in Brazil. Therefore, this study aims at evaluating the performance of eight rootstocks: Aldrighi, Capdeboscq, Flordaguard, Nemaguard, Okinawa, Umezeiro, Tsukuba and Seleção Viamão grafted by ‘Chimarrita’ peach tree, planted in 2006 and evaluated in the 2013/2014, 2014/2015 and 2015/2016 in Capão do Leão, RS, Brazil. The following dependent variables were evaluated on the field: floral phenology, affinity with rootstocks, trunk diameter, crown volume, number of fruits, fruit mass and productivity. Fruit mass, diameter, color, pulp firmness, total soluble solid content, titratable acidity, total phenolic content, total carotenoid content, L-ascorbic acid content and antioxidant activity were evaluated. The Umezeiro rootstock provided the lowest values for crown volume, trunk diameter, number of fruits and productivity. The blossoming period of peach trees can be early or delayed depending on rootstock and harvest seasons. Field compatibility constant of Chimarrita cultivar was higher with the rootstocks of Capdeboscq, Okinawa, Tsukuba and Aldrighi. Fruits of plants grafted on Capdeboscq and Okinawa rootstocks showed reddish epidermis. The Okinawa rootstock enabled ‘Chimarrita’ peaches to have higher soluble solid concentrations and L-ascorbic acid. The highest concentrations of total carotenoids were verified in the pulp of fruits obtained from the ‘Chimarrita’ cultivar grafted on Aldrighi, Okinawa, Tsukuba and Umezeiro. The antioxidant activity of the peach pulp was higher on the Capdeboscq rootstock.


INTRODUCTION
In order to improve peach tree cultivation, its management must be improved with regards to soil preparation, correction and maintenance fertilization, irrigation, phytosanitary control and phytotechnical *Corresponding author.E-mail: carol_fariasb@hotmail.com.Tel: +555599090689.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License management, besides combinations of crown and rootstock cultivars.There is a clear consensus about the need for new studies on rootstocks which aim at increasing production and improving peach quality in Brazil.The main characteristics that rootstocks need to have are control of vigor, fruit size, fruit quality (Neves et al., 2017), productivity and the ability to resist adverse soil and climate conditions.In Brazil, most peach orchards use seed-bearing rootstocks, traditionally from the canning industry.However, these materials are genetically variable, leading to a lack of uniformity in the plants and hindering orchard management (Barreto et al., 2017).Both Aldrighi and Capdeboscq are the most commonly used rootstocks in the south of Brazil since it is easy to get their stones from industries to grow seedlings (Rocha et al., 2007).However, other rootstocks such as Flordaguard, Nemaguard, Okinawa, Umezeiro, Tsukuba and Seleção Viamão have been used as alternatives in terms of fruit adaptation, productivity and quality (Comiotto et al., 2012(Comiotto et al., , 2013;;Galarça et al., 2013).
Studies on crown and rootstock combination in peach trees have shown problems with regards to affinity between these materials.Lack of affinity affects plant growth and development, decreases orchard productivity over time and causes the death of adult plants, besides early death (Pereira et al., 2015).Incompatibility has been an important fact in fruit farming; although there is demand for new rootstocks and crowns, the big challenge is to find adapted genetic material which can multiply easily and seedling production which assures longevity and productivity (Comiotto et al., 2013).
In general, several studies have shown that fruit plants may be influenced by rootstocks because they can affect plant vigor, growth and development besides productivity (Picolotto et al., 2009;Galarça et al., 2013) and fruit quality parameters, such as soluble solids, antioxidants, total phenols, ascorbic acid and flavonoids in the fruit pulp (Remorini et al., 2008;Orazen et al., 2011;Forcada et al., 2013).Therefore, studies on different rootstocks are needed to determine alternatives to replace the most commonly used ones in South Brazil, so that compatible and productive combinations can be established, fruit quality can be achieved and economic benefits can be assured to producers.This is the context of this study, which aims at evaluating eight rootstocks grafted in the "Chimarrita" cultivar.

Location and climatic conditions
The experiment was conducted in a teaching orchard at the Palma Agricultural Center (Centro Agropecuário da Palma; CAP), Federal University of Pelotas (Universidade Federal de Pelotas) in Capão do Leão municipality, Rio Grande do Sul (RS) with Latitude 31°52'00" S and Longitude 52°21'24" W, Brazil.According to the classification of Köppen, the climate of the region is type Cfa, namely humid and temperate with hot summers.The region has an average annual rainfall and temperature of 1500 mm and 17.9°C, respectively.The experiment was conducted during the 2013/2014, 2014/2015 and 2015/2016 seasons.

Treatments and experimental design
The peach orchard used consisted of the P. persica (L.) Batsch Chimarrita cultivar grafted in Aldrighi, Capdeboscq, Flordaguard, Nemaguard, Okinawa, Umezeiro, Tsukuba and Seleção Viamão rootstocks.The orchard was planted in 2006 with a "V" type plantorganization system with 5 m of space between rows and 1.5 m between plants, amounting to a density of 1,333 plants ha -1 .The experimental design involved randomized blocks, with each plot being composed of five plants.The plants at the ends of each plot were disregarded, amounting to nine useful plants.

Traits evaluated
The variables evaluated in the field were: trunk diameter (mm), measured at 20 cm above the soil surface in two transverse positions with the aid of a digital caliper; canopy volume (m 3 ) was calculated using the equation: where V is the volume of the canopy, L is the distance between the main branches, E is the average thickness of the main branches, and A is the height of the canopy.
Field compatibility coefficient (FCC) was calculated using the equation: where A is the trunk diameter above the grafted point, B is the trunk diameter at the grafted point and C is the diameter of the trunk under the grafted point, considering that parameters A and C were measured 10 cm above and 10 cm below the grafted point (Gokbayrak et al., 2007).
Flowering was evaluated by subperiods including early flowering when 10% of the flowers were open, full bloom when 50 to 70% of the flowers were open, late flowering when the petals were falling, and early sprouting when 10% of the fruit were formed.Fruits were monitored until harvest time when the number of fruit per plant (fruit plant -1 ) and productivity (t ha -1 ) were evaluated to determine production amounts.
After harvesting, fresh weights (grams) of the peaches were evaluated by digitally weighing 20 fruit per repetition, totaling 60 fruits.The firmness of the pulp (Newtons), was measured at two opposite points in the equatorial region of peeled fruit using a manual penetrometer (model 53205, TR TURONI-Italy) with an 8 mm tip; color of the epidermis was examined using a colorimeter type Minolta CR-300 ® with a D65 light source that measured "L" (luminosity), "a*", "b*", and hue or chromatic tonality represented by "hue angle"; soluble solids (ºBrix) were measured using an Atago digital refractometer ® ; and titratable acidity (% citric acid) was quantified in 10 mL of juice diluted in 90 mL of distilled water and titrated with 0.1 mol L NaOH solution to pH 8.1 with the aid of Quimus pHmeter ® .
The following analyses were carried out in order to determine the main phytochemical groups or compounds of the peach pulp: total phenolic compounds (mg gallic acid per 100 g of sample) were determined according to the adapted method of Singleton and Rossi (1999) using the reaction with the Folin-Ciocalteau reagent; total carotenoids (mg β-carotene in 100 g of sample) were determined using the modified method of AOAC ( 2005) and an extraction solution (hexane-acetone-alcohol-toluene); and antioxidant activity (mg trolox per 100 g fresh weight) was determined using the radical DPPH method adapted from Brand-Williams et al. (1995); and L-ascorbic acid determined by highperformance liquid chromatography (HPLC), with HPLC Shimadzu system equipped with an automatic injector and a UV-VIS detector (254 nm), in agreement with AOAC (2005) method, and the results are expressed as mg L-ascorbic acid/100 g fresh sample.

Statistical analysis
The data were evaluated for normality (Shapiro-Wilk test) and then subjected to a variance analysis (F-Test), with the means compared using Tukey"s range test to identify significant differences (p ≤ 0.05).

RESULTS AND DISCUSSION
In the 2013/2014 and 2014/2015 seasons, the development and blooming of "Chimarrita" peach trees occurred in weather conditions similar to the traditional ones in the region (South Rio Grande do Sul, Brazil) where the experiment was carried out (Figure 1).In these crops, blooming was uniform and concentrated, that is, at the end of July.However, in the 2015/2016 season, it was strongly affected by the El Niño phenomenon and the behavior of the "Chimarrita" cultivar was characterized by non-uniform blooming on all rootstocks.
Peach trees grafted on Aldrighi, Capdeboscq, Flordaguard, Nemaguard, Tsukuba and Seleção Viamão began blooming (BB) on July 25th, 2013.It occurred five days before Okinawa and Umezeiro started blooming (Table 1).Full blooming (FB) of peach trees occurred on August 15th, 2013, except in the cases of Okinawa and Tsukuba, whose FB occurred seven days earlier (August 8th, 2013).Blooming ended (EB) on August 29th, 2013, except in the cases of Capdeboscq and Nemaguard, whose EB occurred eight days earlier.
The peach trees grafted on Capdeboscq, Flordaguard and Tsukuba began blooming on July 28th, 2014, eight days before the beginning of full blooming of the other   Even though differences in blooming were found among the rootstocks, fruit maturation was similar, regardless of the rootstock, that is, maturation peaks occurred in December 4th, 2013 and November 30th, 2014.
In the region where the experiment was carried out, blooming of the "Chimarrita" cultivar historically occurs in the second week in August (Raseira et al., 2014).Blooming of peach trees occurred irregularly, that is, one of the first blooming periods even occurred two months before the normal period.First blooming began on 16th June, 2015 on Flordaguard, Nemaguard, Okinawa and Umezeiro and on 20th June, 2015 on the other rootstocks.After the first blooming, there was floral abortion on all rootstocks due to temperature oscillation.As a result, the plants had their phenological phases modified.The second blooming occurred at the end of July 2015.None of the rootstocks contributed to production losses in the conditions of the El Niño phenomenon.
Analysis of field compatibility constant of the "Chimarrita" cultivarthe measure of the affinity between the rootstock and the crown cultivar, showed that the values were close to 12 in the case of Capdeboscq (11.82),Okinawa (11.80),Tsukuba (11.80) and Aldrighi (11.76) rootstocks (Figure 2).According to Gokbayrak et al. (2007), when the value is close to 12, the affinity between the crown cultivar and the rootstock on the grafted point is high.
Regarding field compatibility constant, the Umezeiro rootstock had values which were far less than 12 (11.39),a fact that shows incompatibility on the grafted point and excessive development below the point of union.Besides, not only its trunk diameter (2013/2014 and 2015/2016) but also its crown volume (in all three crops) was observed to be smaller (Table 2).This rootstock influenced the crown volume, vigor and diameter of "Chimarrita" peach trees.It may have occurred as a result of the incompatibility of the rootstock and the crown cultivar, which decreases the transport of water and nutrients and reduces the leaf area and the crown volume (Tombesi et al., 2011).Incompatibility between the Umezeiro rootstock and the "Chimarrita" cultivar, besides smaller trunk diameter, was also observed in other regions in Rio Grande do Sul state by Comiotto et al. (2013), Galarça et al. (2013) and Pereira et al. (2015).
Regarding plant growth, the trunk diameter of "Chimarrita" peach trees was observed to vary among crops and rootstocks, but in 2014/2015 season, there was no difference among rootstocks.In 2013/2014 and 2015/2016 seasons, the largest trunk diameters were observed in Flordaguard, Nemaguard, Aldrighi and Seleção Viamão rootstocks.They did not differ statistically from Okinawa, Tsukuba and Capdeboscq.
Umezeiro rootstock with the "Chimarrita" cultivar had low productivity in 2009.The fact that this rootstock leads to low productivity of peach trees may be due to the incompatibility between the grafted point and the crown cultivar.
Productivity of "Chimarrita" peach trees was higher on Tsukuba, Flordaguard, Seleção Viamão, Capdeboscq and Nemaguard rootstocks in 2013/2014 season.Their productivity was higher on Tsukuba rootstock, even though it did not differ from the other rootstocks, except in the case of Umezeiro, in the 2014/2015 season.Both crops had lower productivity of "Chimarrita" peach trees on the Umezeiro rootstock.
Peach mass was larger on plants grown on Flordaguard rootstock in comparison with the other rootstocks in 2013/2014 season.However, there was no difference in this variable in 2014/2015 season.Galarça et al. (2013) observed that seven rootstocks did not change fruit mass of "Maciel" and "Chimarrita" cultivars in three crops.
In "Chimarrita" peach trees, rootstocks did not change pulp firmness (Table 3).However, the color of "Chimarrita" peach epidermis depended on the rootstocks.Fruits of Tsukuba, Nemaguard, Aldrighi, Seleção Viamão, Flordaguard and Umezeiro rootstocks had cream and greenish epidermis, thus, °hue values were high.Fruits of plants grafted on Capdeboscq (75.87 °hue) and Okinawa (65.94 °hue) rootstocks were cream and reddish.Red epicarp is desirable in fruits which are consumed in natura, such as the ones of the "Chimarrita" cultivar.
The "Okinawa" rootstock enabled "Chimarrita" peaches to have higher soluble solid concentrations than the others.It is relevant, since consumers prefer sweetish fruits, an advantage of "Chimarrita" cultivar grafted on Okinawa rootstock, which also provided high values of total soluble solids in the cases of Talismã and Tropical cultivars (Montes et al., 2008).
Variation in concentrations of the main groups of phytochemical compounds (total phenols, L-ascorbic acid, total carotenoids and antioxidant activity) depended on the rootstocks on which the "Chimarrita" cultivar was grafted.Peaches with the highest content of phenolic compounds were yielded by plants grafted on the Okinawa rootstock, whereas the lowest one was found in plants grafted on Flordaguard, Nemaguard, Seleção Viamão and Umezeiro rootstocks.Gil et al. (2002) reported that phenolic compounds are the main sources of antioxidants in peaches and attributed the amount of these compounds to both the crown cultivar and the rootstock.
Regarding the content of L-ascorbic acid, there were also differences among the rootstocks.Its highest concentrations were found in peaches yielded by plants grafted on the Okinawa rootstock, whereas the lowest ones were found on Aldrighi, Nemaguard and Tsukuba rootstocks.The highest concentrations of total carotenoids were found in the pulp of fruits yielded by the "Chimarrita" cultivar grafted on Aldrighi and Okinawa rootstocks, whereas the lowest ones referred to the Seleção Viamão rootstock.The antioxidant activity of the peach pulp was higher on the Capdeboscq rootstock than on the others.
Variation in fruit phytochemicals among rootstocks may be due to the capacity of plants to absorb nutrients which are available in the soil and efficiency in converting the assimilated compounds to fruits.Phytochemicals are affected by combinations between rootstocks and crown cultivars.However, the phytochemicals under analysis do not have similar behavior.Besides the rootstocks, other factors such as harvest conditions, position of fruits in the plant, genotype (Forcada et al., 2013), weather conditions, off season period and maturation stage (Daza et al., 2008), can affect fruit quality.

Conclusion
The Umezeiro rootstock reduces the crown volume, trunk diameters, number of fruits and productivity of the "Chimarrita" cultivar in south Brazil.Fruits of plants grafted on Capdeboscq and Okinawa rootstocks showed reddish epidermis.The Okinawa rootstock enabled peaches to have higher soluble solid concentrations and L-ascorbic acid.The highest concentrations of total carotenoids were verified in the pulp of fruits yielded by the "Chimarrita" cultivar grafted on Aldrighi, Okinawa, Tsukuba and Umezeiro.The antioxidant activity of the peach pulp was higher on the Capdeboscq rootstock.

Figure 1 .
Figure 1.Mean temperature and hour of cold in 2013, 2014 and 2015 and normal ones in Capão do Leão, Rio Grande do Sul, Brazil, Terras Baixas Experimental Station.Embrapa Clima Temperado.
Means followed by the same small letter do not differ by the Tukey"s test at 5% error probability.VC (%) = variation coefficient.ns = not significant.(-) Peach trees did not yield.

Table 3 .
Epidermis color, pulp firmness, soluble solids, total phenols, ascorbic acid, total carotenoids and antioxidant activity of "Chimarrita" peach trees on different rootstocks in the municipality of Capão do Leão, Rio Grande do Sul, Brazil, for the 2014/2015 season.