Initial production and fruit quality of fifty-seven sweet orange varieties on four rootstocks in Southern state of Bahia

- Prior knowledge of scion/rootstock combinations is essential for establishing appropriate citrus orchard management strategies. The objective of this work was to assess the initial yield and fruit quality among 228 scion/rootstock combinations set up in the municipality of Ibirapuã, extreme south of the state of Bahia in 2015. Harvests were carried out from April to August 2019, when trees reached 4 years of age. Number, total mass and cross-sectional diameter of fruits, productive efficiency, pulp yield, soluble solids content, titratable acidity and SS/AT ratio were evaluated. Statistical difference for all characteristics related to production and fruit quality regarding factors studied and their combinations was observed. Among ‘Pera’ orange clones, ‘Pera CNPMF A-15’/‘San Diego’ citrandarin and ‘Pera CNPMF D-3’/‘Riverside’ citrandarin combinations stood out. ‘Sincorá’ orange, in combination with ‘San Diego’ and ‘Indio’ citrandarins presented potential to be recommended to producers who wish to anticipate their harvests, as well as ‘Natal Ipeal’ orange in combination with ‘Indio’ citrandarin, in the sense of postponing them.

Citrus are among the most cultivated fruit species in the world, mainly in subtropical and tropical climates.The main citrus product in the Brazilian scenario is intended for industry, for the production of frozen concentrated orange juice for export, of which Brazil accounts for 50% of the total world production, followed by the United States (FAO, 2015).The Brazilian production of sweet oranges [Citrus sinensis (L.) Osbeck], in 2019, was approximately 17.6 million tons in an approximate area of 608.2 thousand hectares of harvested area, especially in the states of São Paulo.Paulo, Minas Gerais, Paraná and Bahia, with the highest productions, respectively (IBGE, 2020).
Despite the wide variety of genetic material from sweet oranges, the national citrus industry predominantly uses 'Pera' and 'Valencia' orange cultivars on 'Rangpur' and 'Citrumelo Swingle' rootstocks.This makes crops susceptible to losses due to the onset of diseases such as Phytophthora gummosis, citrus tristeza virus and citrus sudden-death (FADEL et al., 2018;RODRIGUES et al., 2016;SOARES;et al., 2015).
With the objective of proposing new rootstock options for the national citrus industry, crosses between 'Sunki' mandarins [Citrus sunki (Hayata) hort.ex Tanaka] and 'Cleopatra (Citrus reshni hort.ex Tanaka) with trifoliata [Poncirus trifoliata (L.) Raf.] have been performed, giving rise to hybrids called citrandarins, which have great potential for use as rootstock.This type of crossing aims to add characteristics present in mandarins, such as less susceptibility to citrus exocortis viroid, citrus decline, citrus tristeza virus and citrus sudden-death.For P. trifoliata, studies seek to add resistance to Phytophthora gummosis and citrus tristeza virus, adaptation to low temperatures and soils subject to flooding, in addition to inducing size reduction to scion varieties grafted on them, which characteristic is verified particularly in 'Flying Dragon' cultivar (POMPEU JUNIOR;BLUMER, 2009).Among mandarins, 'Tropical Sunki' stands out, which has as main characteristics high number of seeds per fruit, polyembryony degree close to 100% and greater tolerance to Phytophthora gummosis, compared to other selections of this mandarin (SOARES FILHO et al., 2002).
To achieve success in the citrus activity, with fruit yield and quality, it is not enough just to analyze the different scions of sweet oranges and rootstocks alone, but their combinations.These interactions can induce behavioral variations, making it necessary to study scion/rootstock combinations.Another factor that suffers interference and is directly linked to the success of the scion/rootstock combination refers to fruit production, which may also vary according to the interaction of the genotype with the environment (SCHÄFER et al., 2001;PRUDENTE;SILVA, 2006).Therefore, prior knowledge of rootstock combinations with orange scions is important to establish crop management strategies.In this sense, the objective of this study was to identify among 228 scion/rootstock combinations those that present the best productive aspects and fruit quality in the extreme south of the state of Bahia.
The experiment was carried out in an experimental area of Fazenda Chão Bello, municipality of Ibirapuã, extreme southern Bahia (17°48'08.1''S,39°52'09.8''W)and altitude of 95 m a.s.l.The climate is classified as tropical humid or sub-humid (Am), according to the Köppen classification, with average annual temperature of 23.6 °C (ALVARES et al., 2013).Average monthly rainfall was 76.3 mm between January 2018 and December 2019, according to data collected from the rain gauge installed in the experimental area.
The experiment was installed in the field on 04/12/2015 with spacing of 6 m between rows and 3 m between plants.The irrigation system used was microsprinkler with flow of 72 L/h, in two fixed irrigation shifts of 6 mm/day.Fertilization was carried out according to recommendations from the partner citrus grower.For phytosanitary control, fungicides and insecticides registered for the crop were used, according to periodic monitoring in the area.To control weeds in planting rows, herbicides based on glyphosate and glufosinate were applied.Cultural treatments such as mowing between rows and plant pruning were carried out in accordance with the producer's management and to standards recommended for the crop.
In 2018, due to the low yield, harvest was carried out only with the purpose of verifying the harvest time of the different scion/rootstock combinations.Based on 2018 data, harvests were carried out from April to August 2019, evaluating the following morphoagronomic parameters: total number of fruits (NTF, per plant), total fruit weight (MTF, kg/plant), plant height (ALT, m), mean scion diameter in the row direction (DL, m) and between rows (DE, m).Fruits were manually collected, counted, placed in collection boxes suitable for transport and weighed on scale installed in the experimental area.ALT and scion diameters (DL and DE) were measured using measuring tape graduated in centimeters, and data were used to calculate the scion volume (VC, m 3 ), obtained according to Zekri et al. (2003), by the formula: where: ALT = plant height (m); DL = scion diameter in the row direction; DE = scion diameter (m) perpendicular to the planting row.
Productive efficiency per plant (EP, kg.m -3 ) was obtained by the relationship between MTF and VC.
For physicochemical evaluations, samples of six fruits per experimental plot were used, taken from the middle third of scions, packed in polyethylene bags, identified and taken to the laboratory.The following characteristics were evaluated: cross-sectional diameter (DT, mm) measured with digital caliper; juice yield (REND, %) through industrial blender, measuring the percentage of the difference between sample and waste masses (bagasse and seeds); soluble solids content (SS, °Brix) with digital refractometer; titratable acidity (AT, % citric acid) determined by volumetry and using phenolphthalein solution as indicator; and the SS/AT ratio.
Data were submitted to analysis of variance (ANOVA) and the Scott-Knott test was applied to compare treatments at 5% probability using the R software (R DEVELOPMENT CORE TEAM, 2011).
In relation to total fruit mass (MTF), the combination between 'San Diego' citrandarin and 'Sincorá' orange showed greater expression of this character (Table 3).It is noteworthy that in this scion, higher MTF values were observed in the four rootstocks (Figure 1), with emphasis on 'San Diego' and 'Indio' citrandarins (115.64 and 111.1 kg/plant) with average masses per fruit of 254 and 214 g respectively, superior to results found by Coelho et al. (2019), with average mass for 'Pera Rio' cultivar, in conventional system, of 204 g per fruit.'Pera Olímpia/ 'Riverside' citrandarin and 'Pera GE-03/ Indio' citrandarin combinations also presented MTF above 100 kg/plant; however, lower averages, of 200 and 184 g per fruit, respectively.Based on observed data, 'Sincorá' orange can be an alternative to 'Pera' and 'Natal' oranges in extreme south of the Bahia.However, future evaluations should be carried out to confirm or not these results.
Taking into account the spacing adopted in this study and according to IBGE (2020), 40.35% of scion/ rootstock combinations evaluated presented yield higher than the national average of 28.96 t.ha -1 in 2019, above 52.08 kg/plant.'Riverside' citrandarin stood out, which induced fruit yields above 60 kg per plant in all 'Pera' orange selections, according to Bastos et al. (2014), justifying its excellent behavior when grafted with sweet orange trees.It is noteworthy that yields presented here were obtained with 4.5-year-old plants.
It should be noted that greater amount of fruits may reflect greater total fruit mass, as observed, since of the 19 combinations that had the highest average NTF, 15 also presented higher MTF than the others.However, these characteristics may not indicate increase in productive gains, since, in their totality, small fruits, non-commercial standard and vigorous plants with excessive growth are taken into account.Thus, NTF and MTF should not be used solely as a way of selecting the most advantageous combinations, requiring evaluating other variables related to fruit production and quality, such as productive efficiency, total acidity and soluble solids content of produced fruits.
Among combinations with the highest EP values, 'Pera CNPMF-02' and 'Pera CNPMF A-15' on 'San Diego' citrandarin stand out, with 9.29 and 10.88 kg of fruits.m - of scion, respectively.These 'Pera' orange selections did not show statistically significant differences for total fruit mass among rootstocks studied, the same not being true in relation to productive efficiency.This fact, as observed by Carvalho et al. (2016), relates to the effect of the rootstock on the size or volume that induces to scion variety, verifying that smaller scions, which have smaller amount of fruits per plant compared to larger scions, can, on the other hand, show greater fruit production per scion volume unit, that is, high fruit production efficiency.
'Pera Olímpia' orange stood out for presenting the highest EP value on the four rootstocks evaluated, notably in relation to 'San Diego', 'Riverside' and 'Indio' citrandarins, with 9.23, 8.56 and 9. 23 kg of fruits.m - scion, respectively.These values are in line with those obtained by Carvalho et al. (2016) in 'Pera CNPMF-D6' orange scions on these citrandarins.There is, therefore, evidence that these rootstocks have great potential for commercial use in the extreme south of the state of Bahia in combination with 'Pera' orange.
Rev. Bras.Frutic., Jaboticabal, 2021, v. 43, n. 5 (e-765) Initial production and fruit quality of fifty-seven sweet orange varieties on four rootstocks in Southern state of Bahia   High productive efficiencies allow for increases in productivity per cultivated area (Lima et al., 2014).Rootstocks inducing high fruit productive efficiency in association with reductions in scion size are suitable for the use of high planting densities, enabling substantial reductions in the planted area without reducing fruit production, which is relevant for large and small producers who want higher yields in their crops.According to Blumer (2005), scion/rootstock combinations with these characteristics are advantageous, since, according to Carvalho et al. (2005), the productive scenario of modern citriculture foresees the use of dense planting spacing, which facilitates harvesting, pesticide application and cultural treatments in general.Santos et al. (2016) corroborate this opinion.On the other hand, as described by França et al. (2016), low productive efficiency may be associated, in some cases, with excess vegetative growth and not with lower fruit production per plant.
Regarding the harvest time, no influence of rootstocks on scions was observed.It was observed that the earliest scion varieties in this study, with harvests recorded from April to June, were 'Sincorá', 'Early Oblong', 'Salustiana', 'Westin', 'Crescent sweet' and 'Flor de Brumadinho'.The latest scion varieties were 'Hamlin CNPMF-20', 'Melrosa' and all 'Natal' and 'Valencia' selections, which had fruits harvested in August.'Berna', 'Jaffa', 'F-Menuda', 'Aquiri', 'Russas', 'Seleta de Itaboraí' and 'Pineapple' scions, as well as 'Pera' selections, concentrated ripe fruits in the month of June.Due to the large number of combinations, fruit maturation curve analysis was not performed; however, after determining the best scion/rootstock combinations in relation to production and productive efficiency, this analysis will be performed.
Producers who want to scale their production must pay attention not only to production characteristics, but also choose scion/rootstock combinations that meet their planning and quality standards established by the consumer market, whether for fresh fruits or orange juice.
Fruit quality variations were observed, both in relation to scion cultivars and rootstocks, as well as regarding the interaction between them (Table 5).Several environmental factors and cultivation practices can influence the quality of citrus fruits.The relationship between scion and rootstock is among the most important, whose interaction has implications for the absorption of water and nutrients and hormonal effects, with direct influence on juice quality (LIU et al., 2015;LADO et al., al., 2018).
The largest cross-sectional fruit diameters (DT) were observed in 'F-Menuda', 'Seleta de Itaboraí' and 'Melrosa' scion cultivars on 'Sunki Tropical' mandarin and in 'Seleta de Itaboraí', 'Valencia Midknight' and 'Melrosa' scion cultivars on 'San Diego' citrandarin (Table 6).Regarding 'Riverside' citrandarin, the highest values for this variable were found for 'Aquiri', 'Seleta Table 5. Summary of the analysis of variance with sources of variation (FV), degrees of freedom (GL), mean squares of the residue (QMR) and coefficients of variation (CV) for variables cross-sectional fruit diameter (DT), soluble solids (SS), titratable acidity (TA), SS/AT ratio and juice yield (REND) of 57 sweet orange varieties [Citrus sinensis (L.) Osbeck] in combination with four rootstocks.The overall mean for the 26 combinations with the highest DT values was 89.27 mm.'Seleta de Itaboraí' and 'Melrosa' cultivars presented higher DT values in the four rootstocks.However, according to the Ceagesp classification (2011), regarding the class of sweet and low-acidity oranges, it was observed that more than 94% of combinations evaluated in this study fall into class of 'large' fruits, with DT above 71 mm, rated 'A' and the others rated 'B', with 'intermediate' size, between 65 and 71 mm.
'Indio' citrandarin, in 53% of combinations, was the rootstock that induced the highest average DT value.According to Liu et al. (2015), the diameter of citrus fruits is related to the rootstock used, as it influences plant metabolism, regulating hormonal interactions and cell size.Therefore, in cases where the aim is production to supply the fresh fruit market, both scion variety and rootstock variety must be properly defined for the orchard implantation.
Differences were observed among combinations regarding the soluble solids (SS) content of fruits.Among combinations, 22% had fruits with values equal to or greater than 10 °Brix, which, according to the Ceagesp classification (2011), qualifies them for consumption as good quality fresh fruits (Table 7).It is noteworthy that some of scion varieties under study are of low AT, such as 'Berna', 'Aquiri', 'Pera de Ibotirama', 'Seleta de Itaboraí', 'Westin', 'Diva', 'Crescent sweet', 'Melrosa' and 'Flor de Brumadinho'.These materials are accepted for fresh consumption, exclusively, being especially recommended for children, pregnant women and older adults.In addition, fruits from late maturing orange trees, prematurely harvested, like 'Natal' and 'Valencia' clones did not reach their ideal maturation point, yet more than 80% of the 228 scion/ rootstock combinations showed ratio values equal to or greater than 9.5, which is considered as the minimum required for good quality fruits (CEAGESP, 2011).For the orange juice consumer market, according to Pozzan and Triboni (2005), SS/AT ratio values between 14 and 16 are more acceptable, which are values observed in only 15.78% of evaluated combinations.In addition, as previously reported, due to the numerous combinations, the maturation curve was not carried out, which will be carried out after selecting the most productive and with better productive efficiency.
Regarding juice yield (REND), it was observed that combinations differed statistically, with the highest yields being observed in 74 combinations, among them 'Pera CNPMF E-6/ 'Riverside' citrandarin, with 58.11% (Table 10).The combinations under study, except for 'F-Menuda'/ 'Sunki Tropical' mandarin, presented desirable juice yield for fresh consumption, according to the Codex Alimentarius (2005), with values equal to or greater than 35%.However, for Ceagesp (2011), the minimum juice yield for 'Pera', 'Natal', 'Valencia' and 'Hamlin' orange varieties must be, respectively, 45%, 44% and 35%.It is noteworthy that for industry use, small variations in this index can lead to large differences in the final juice production.
Although preliminary, the results obtained in this study allowed the identification of promising scion/ rootstock combinations, particularly for citrus crops in the extreme south of the Bahia and Espírito Santo.
Variety from mid-season to late ripening, 'Sincorá' stood out in combination with 'San Diego' and 'Indio' citrandarins in relation to fruit production and juice quality, although it did not present acceptable values in terms of soluble solids content, considering recommendations for fruits intended for fresh consumption.
It should be kept in mind; however, that this is a first fruit crop, a situation that can change in later crops, since fruit quality is lower in the first crops than in more advanced ones.Among late maturing varieties, such as 'Natal' and 'Valencia' selections harvested in August, the 'Natal Ipeal'/ 'Indio' citrandarin combination stood out for its high efficiency in fruit production and pulp yield, despite the low fruit acidity (0.69%, citric acid), acceptable for industry, it reached ratio of 14.13, a desirable characteristic for fresh consumption.
Among scion/rootstock combinations that showed high productive efficiency levels, considering those harvested in June, the most prominent were 'Pera CNPMF A-15/ 'San Diego' citrandarin and 'Pera CNPMF D-3/ 'Riverside' citrandarin, which met criteria established by the market regarding fruit quality: ºBrix of 11.6 and 10.6, total acidity of 1.04% and 0.76%, ratio of 11.33 and 14.00 and juice yield of 55.23% and 50.88%, respectively.However, it was observed that depending on the purpose (industrialization or fresh consumption), growing conditions and harvest time, this indication may vary.Considering that the results obtained are preliminary, as well as the place where the study was carried out, the following conclusions are listed below: 1.There are indications that 'Pera CNPMF A-15/ 'San Diego' citrandarin and 'Pera CNPMF D-3/ 'Riverside' citrandarin combinations can be used in the production of fruits for both industry and fresh consumption.
2. Both 'Sincorá' variety in combination with 'San Diego' and 'Indio' citrandarins, and 'Natal Ipeal' variety in combination with 'Indio' citrandarin, present strong indications of the possibility of recommendation to citrus growers, the former being of earlier maturation compared to the latter.
We would like to thank the Espírito Santo Research and Innovation Foundation (FAPES), the Coordination for the Improvement of Higher Education Personnel (CAPES), Bello Fruit -BA and Embrapa Mandioca e Fruticultura.
Means followed by the same uppercase letter in the row and lowercase in the column do not differ by the Scott-Knott mean cluster test at 5% probability.Rev.Bras.Frutic., Jaboticabal, 2021, v. 43, n. 5: (e-765) S. B.Buffon et al.