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Scientia Horticulturae
j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / s c i h o r t i
Performance of ‘Tahiti’ lime on twelve rootstocks under irrigated and
non-irrigated conditions
Erick Espinoza-Nú ˜nez
a, Francisco de Assis Alves Mourão Filho
a,∗, Eduardo Sanches Stuchi
b,
Tatiana Cantuarias-Avilés
a, Carlos Tadeu dos Santos Dias
aaUniversidade de São Paulo, Escola Superior de Agricultura “Luiz de Queiroz”, 13418-900 Piracicaba, SP, Brazil bEmbrapa Mandioca e Fruticultura Tropical, Estac¸ão Experimental de Citricultura de Bebedouro, Bebedouro, SP, Brazil
a r t i c l e
i n f o
Article history:
Received 6 October 2010
Received in revised form 14 March 2011 Accepted 18 March 2011
Keywords: Citrus latifolia
Dwarfing Flying Dragon High density planting Interstock
Poncirus trifoliata
a b s t r a c t
Faced with new challenges, such as emerging diseases, shortening of orchard longevity, and larger social and environmental demands from consumers, practices such as rootstock diversification, irrigation and high density plantings have become relevant for the Brazilian citrus industry. This research had the objective to evaluate the performance of irrigated and non-irrigated ‘Tahiti’ lime trees grafted on 12 rootstocks and one interstock. Plots were distributed following a randomized block design, with four replicates and one plant per plot. Rootstocks influenced plant vigor, especially ‘Flying Dragon’ trifoliate, which reduced tree height by approximately 47% compared to the ‘Rangpur’ lime. Trees that were budded on more vigorous rootstocks showed higher yield when grown without irrigation than with irrigation. The ‘1646’ citradia and ‘Morton’ citrange rootstocks performed particularly well. On the other hand, the plants on less vigorous rootstocks showed better performance in terms of yield under irrigation than the same combinations without irrigation, especially those grafted on the tetraploid ‘Carrizo’ and ‘Troyer’ citranges, ‘Swingle’ citrumelo, ‘Davis A’ trifoliate and ‘Flying Dragon’ trifoliate. Plants budded on the ‘1708’ citradia had high yields under irrigated and non-irrigated conditions. The effect of interstock on plant vigor was dependent of rootstock. Interstocked plants on ‘Davis A’ trifoliate were higher than those without interstock. On the other hand, interstocked plants on Catania 2 ‘Volkamer’ lemon were less vigorous than those without interstock.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
The citrus industry faces new challenges worldwide, including emergence of diseases, shortening of orchard life span, and lar-ger social and environmental demands imposed by consumers. In Brazil, four varieties of sweet orange represent nearly 92% of the citrus plants in the State of São Paulo, and a single type of rootstock, the ‘Rangpur’ lime, accounts for 85% of the rootstocks used in citrus
groves (Bové and Ayres, 2007). In this context, rootstock
diver-sification, irrigation and high density planting practices become relevant.
On the other hand, production and international market of ‘Tahiti’ lime have significantly expanded in the recent years. In order to sustain this developing market, it is very important to create adequate conditions to extent ‘Tahiti’ lime harvest period, with rootstock diversification and irrigation. Over 85% of the citrus groves in Brazil are not irrigated. Experiments involving ‘Tahiti’
∗Corresponding author. Tel.: +55 19 34294190; fax: +55 19 34294385.
E-mail address:francisco.mourao@usp.br(F.A.A. Mourão Filho).
lime are scarce, but the partial results already allow to characterize
some rootstocks (Stuchi et al., 2003; Stenzel and Neves, 2004).
Considering that there has been a growing interest in ‘Tahiti’ lime production driven by the need for higher crop yields and the possibility of producing fruit during the off-season period, at higher market prices, the objective of this study was to evaluate the per-formance of irrigated and non-irrigated ‘Tahiti’ lime trees budded on 12 rootstocks and on one interstock.
2. Materials and methods
2.1. Field trial and plant material
Trees were planted in December of 2003 in the northern São
Paulo State, Brazil (20◦53′16′′S latitude; 48◦28′11′′W longitude;
601 m altitude) on an 8.0 m×5.0 m tree spacing, corresponding
to a plant density of 250 trees ha−1. The soil was Haplustox with
a medium texture (38% clay), and the climate was Köeppen’s
Cwa, with maximum and minimum temperatures of 30.5◦C and
16.8◦C, respectively, and an annual rainfall of 1534.7 mm.
‘IAC-5’ ‘Tahiti’ lime (Citrus latifolia (Yu. Tanaka) Tanaka) was grafted
on the following rootstocks (treatments): the trifoliates ‘Flying
Dragon’ (Poncirus trifoliata) and ‘Davis A’; the tetraploid ‘Troyer’
and ‘Carrizo’ citranges and the ‘Morton’ citrange [Citrus sinensis
(L.) Osbeck×P. trifoliata]; the citradias (Citrus aurantium×P.
tri-foliata) ‘1646’ and ‘1708’; ‘Swingle’ citrumelo (Citrus paradisi×P. trifoliata); Catania 2 ‘Volkamer’ lemon (Citrus volkamerianaV. Ten.
& Pasq.); ‘Orlando’ tangelo (Citrus reticulataBlanco×C. paradisi
Macf.); ‘Smooth Flat Seville’ (SFS) (C. aurantiumL.) sour orange and
the ‘Rangpur’ lime (Citrus limoniaOsbeck). ‘Flying Dragon’
trifo-liate was also used as interstock for Catania 2 ‘Volkamer’ lemon, ‘Orlando’ tangelo, ‘Morton’ citrange, ‘Swingle’ citrumelo, ‘SFS’ sour orange, and ‘Davis A’ trifoliate. Plants grafted on ‘Orlando’ tangelo (not interstocked) and on ‘SFS’ sour orange (interstocked) died in
2007 due to root rot caused byPhytophthoraspp. The experiment
was not pruned, and was managed according with regular cul-tural practices. The annual rate of fertilization was equivalent to
190 g N, 110 g P and 116 g K tree−1as mono ammonium phosphate
and 20–0–20. The experimental orchard was surrounded by several other citrus evaluation experiments.
2.2. Plant yield and fruit quality measurements
Plant height (H) and width (in parallel,Dl, and perpendicular,
Dr, direction to the row) were measured, in 2009 to calculate the
canopy volume according to the equation V= (/6)×H×Dl×Dr
(Zekri, 2000). Fruit harvests were recorded from 2007 to 2009. Under local conditions, ‘Tahiti’ limes bloom throughout the entire year, leading to a total of three to five harvests evaluated each year. In 2009, yield efficiency was computed from the relations-hip between the fruit yield (kilograms per plant) and the canopy
volume (cubic meters per plant). Yield (kg tree−1) was recorded
on every commercial harvest, and cumulative yield was calcula-ted for two periods, which include the following: from the second year through the fourth year after planting (2005–2007) to estimate early-bearing cumulative yield and from the second year through the sixth year after planting (2005–2009) to evaluate total cumu-lative yield.
2.3. Experimental design and statistical analysis
The plots were distributed following a randomized block design, with 18 treatments, four replications and one plant per plot. The same experiment was conducted both with and without irrigation. In the irrigated experiment trees were drip irrigated based on a
100% of the crop evapotranspiration (ETc). The system was
com-prised of a drip line in each tree row, with three self-compensating
drippers (2.3 l h−1) per tree, which were 1.0 m apart. For each
variable, row data were initially submitted to exploratory analy-sis to verify whether they meet the assumptions of homogeneity of variances, normality of errors, and presence of outliers. Data were submitted to analysis of variance, using Fisher’s test. Origi-nal data of some variables were transformed using the Box Cox
method (Montgomery, 2005). For each variable, the individual and
joint analyses of variances were performed. Comparisons among
means were performed by the Scott Knott test (P< 0.05), while the
effect of interstock was tested by contrasts.
3. Results
3.1. Plant height and canopy volume
The rootstock clearly affected plant growth. In the non-irrigated experiment, the more vigorous plants reached approximately 3.6 m
in height and had 33 m3of canopy volume, while in the irrigated
experiment, the more vigorous plants were 4.0 m in height and had
45 m3of canopy volume six years after planting. In both
experi-ments, the rootstock that produced the most vigorous ‘Tahiti’ lime plants were Catania 2 ‘Volkamer’ lemon, ‘Orlando’ tangelo,
‘Mor-ton’ citrange and ‘Swingle’ citrumelo (Table 1). In the non-irrigated
trial, plants with intermediate vigor were approximately 3.2 m in
height, with 26 m3of canopy volume, while in the irrigated trial,
plants were 3.7 m in height and had 36 m3of canopy volume. In
both experiments, the rootstocks ‘Rangpur’ lime, the ‘1646’ and ‘1708’ citradias, the tetraploid ‘Carrizo’ and ‘Troyer’ citranges and the ‘Davis A’ trifoliate induced intermediate vigor to the ‘Tahiti’ lime scion. In both experiments, ‘Flying Dragon’ trifoliate and ‘SFS’
sour orange rootstocks induced plant dwarfing (Table 1). Low vigor
(or dwarf) plants had their canopy volume reduced by one-third to one-half compared to ‘Rangpur’ limes. Irrigation promoted vegeta-tive plant growth on all the rootstocks; plant height was increased by 11% and the canopy volume by approximately 36%.
The interstock had no effect on plant height and canopy volume in both experiments. Some contradictory and unexpected effects of interstock were observed, such as increasing plant vigor on ‘Davis A’ trifoliate and decreasing plant vigor on Catania 2 ‘Volkamer’ lemon (Table 1).
3.2. Yield
In the fourth year after planting, fruit yield in the irrigated experiment was 149% larger than in the non-irrigated experiment,
demonstrating the influence of irrigation on early yield (Table 2).
In the fifth and sixth years after planting, higher yields were obser-ved in plants on Catania 2 ‘Volkamer’ lemon, ‘1646’ citradia, ‘1708’ citradia, ‘Orlando’ tangelo, ‘Morton’ citrange and ‘Swingle’
citru-melo (Table 2). Rootstocks influenced the early-bearing cumulative
yield (second year through fourth year after planting) (Table 3). In
the non-irrigated experiment, the rootstocks Catania 2 ‘Volkamer’ lemon, ‘1646’ and ‘1708’ citradias, ‘Orlando’ tangelo and ‘Mor-ton’ citrange induced a larger percentage of early-bearing yields. In the irrigated experiment, larger early-bearing was observed on the ‘1646’ and ‘1708’ citradias as well as on the ‘Morton’ citrange (Table 3). Furthermore, trees on ‘Volkamer’ lemon and ‘Orlando’ tangelo acted similarly in both experiments. These results indica-ted that irrigation induced higher fruit yields in most rootstocks, including a 257% increase in the ‘Rangpur’ lime, a 379% increase in the ‘Carrizo’ citrange tetraploid, a 324% increase in the ‘Troyer’ citrange tetraploid, and a 432% increase in the ‘Davis A’ trifoliate (Table 3).
Rootstocks also influenced the cumulative yield, from the
second year through the sixth year after planting (Table 3). In both
experiments, larger cumulative yields were observed for plants on Catania 2 ‘Volkamer’ lemon, the ‘1646’ and ‘1708’ citradias,
‘Orlando’ tangelo and ‘Morton’ citrange (Table 3). The interstock
induced higher fruit production in plants on ‘Davis A’ trifoliate in both experiments. The irrigated plants produced an average of 42% more fruits than non-irrigated ones. Paradoxically, ‘1646’ citradia, ‘Orlando’ tangelo, ‘SFS’ sour orange and ‘Flying Dragon’ trifo-liate rootstocks produced similarly in both experiments. However, plants grafted on tetraploid ‘Carrizo’ and ‘Troyer’ citranges, ‘Swin-gle’ citrumelo and ‘Davis A’ trifoliate increased their cumulative
production by more than 60% when irrigated (Table 3).
Yield efficiency after six years from planting was affected by the
rootstocks (Table 3). In the non-irrigated experiment, the plants
Table 1
Plant height and canopy volume of ‘Tahiti’ lime on different rootstocks, interstocked or not interstocked, under irrigated and non-irrigated conditions. Brazil, 2009.
Rootstocks Interstock Non-irrigated experiment Irrigated experiment
Plant height (m) Canopy volume (m3) Plant height (m) Canopy volume (m3)
‘Rangpur’ lime – 3.33±0.10b 24.58±1.1b 3.65±0.02b 38.57±1.4b
Catania 2 ‘Volkamer’ lemon – 3.65±0.08a 31.45±0.9a 4.10±0.05a 49.94±1.0a
Catania 2 ‘Volkamer’ lemon ‘Flying Dragon’ 3.23±0.09b 29.01±1.3b 3.97±0.10a 45.00±1.3a
‘1646’ citradia – 3.35±0.21b 31.06±2.8a 3.70±0.23b 34.85±4.3b
‘1708’ citradia – 3.18±0.08b 28.22±1.5b 3.77±0.06b 34.91±1.3b
‘Orlando’ tangelo ‘Flying Dragon’ 3.75±0.06a 40.62±0.5a 4.02±0.15a 46.24±2.2a
‘Morton’ citrange – 3.61±0.18a 35.89±5.0a 4.17±0.03a 46.78±1.0a
‘Morton’ citrange ‘Flying Dragon’ 3.73±0.12a 36.52±1.9a 4.23±0.13a 52.20±2.1a
‘Carrizo’ citrange tetraploid – 3.46±0.06a 25.95±2.1b 3.78±0.09b 37.59±2.6b
‘Troyer’ citrange tetraploid – 3.45±0.02a 26.86±2.6b 3.89±0.21a 36.40±3.5b
‘Swingle’ citrumelo – 3.54±0.15a 33.68±3.2a 3.93±0.03a 40.89±3.2b
‘Swingle’ citrumelo ‘Flying Dragon’ 3.62±0.12a 29.36±1.3b 3.90±0.00a 38.14±2.4b
‘Davis A’ trifoliate – 3.08±0.20b 24.21±3.4b 3.39±0.11c 33.90±4.3b
‘Davis A’ trifoliate ‘Flying Dragon’ 3.44±0.09a 27.51±1.5b 3.64±0.09b 33.92±3.4b
‘Flying Dragon’ trifoliate – 2.33±0.12c 8.06±1.2d 2.44±0.07d 13.76±0.8d
‘SFS’ sour orange – 2.59±0.10c 13.47±1.1c 3.20±0.18c 22.03±3.1c
Mean 3.33 27.90 3.73 37.82
CV (%) 7.21 3.43 5.78 2.90
Contrast
Non-interstocked plants 3.47a 31.30a 3.90a 42.88a
Interstocked plants 3.50a 31.60a 3.93a 42.33a
Interaction Rootstocks×Irrigation in plant height (P= 0.4142) and canopy volume (P= 0.2819). Means followed by different letters in columns are significantly different (P< 0.05) by Scott Knott’s test. Values represent means±SE.
and ‘Flying Dragon’ trifoliate. In general, non-irrigated plants on less invigorating rootstocks showed higher yield efficiency than the plants watered and grafted on more invigorating rootstocks (Table 3).
4. Discussion
The low vigor and high yield efficiency traits of plants bud-ded on ‘Flying Dragon’ trifoliate suggest that this rootstock is
suitable for high density plantations (Stuchi et al., 2003;
Cantuarias-Avilés et al., 2010). Plants on ‘Flying Dragon’ trifoliate occupied an
area of 5.78 m×2.79 m in the irrigated experiment and an area
of 5.05 m×2.17 m in the non-irrigated trial, as calculated from
plant diameter measured after 6 years from planting, assuming
15% of tree overlapping along the row (De Negri et al., 2005). These
plant spacings, however, corresponded to six-year-old plants. The-refore, lower plant density would be expected when the plants reach their final size. Researchers have recommended planting spacings of 5.5–6.0 m between the rows, and 1.0–2.0 m between plants along the row for ‘Tahiti’ limes on ‘Flying Dragon’
trifo-liate (Stuchi and Silva, 2005). In this recommendation, however,
the overlapping between canopies seems to exceed 15%. Another important feature of ‘Flying Dragon’ trifoliate rootstock is its high
resistance to root rot caused byPhytophthoraspp., observed even
in irrigated orchards (Stuchi and Silva, 2005). Nonetheless, ‘Flying
Dragon’ trifoliate seems inappropriate as a rootstock for ‘Hamlin’
Table 2
Fruit yields in the fourth, fifth and sixth years after planting of ‘Tahiti’ lime on different rootstocks, interstocked or not interstocked, under irrigated and non-irrigated conditions. Brazil, 2009.
Rootstocks Interstock Non-irrigated experiment Irrigated experiment
Fourth (kg tree−1) Fifth (kg tree−1) Sixth (kg tree−1) Fourth (kg tree−1) Fifth (kg tree−1) Sixth (kg tree−1)
‘Rangpur’ lime – 16.9±3.2b 47.8±2.6a 101.5±13.3c 48.9±3.0b* 58.9±4.7b 114.8±6.9b
Catania 2 ‘Volkamer’ lemon – 37.4±8.2a 68.7±8.5a 121.7±14.3b 60.6±5.5a* 88.9
±5.4a 178.7±5.3a Catania 2 ‘Volkamer’ lemon ‘Flying Dragon’ 34.9±10.3a 78.8±5.9a 124.1±11.6b 40.7±1.7b 107.0±10.5a 147.4±17.3b ‘1646’ citradia – 31.2±3.3a 60.7±9.9a 137.0±5.1b 60.8±8.9a* 67.3
±3.8b 146.2±11.6b ‘1708’ citradia – 33.6±3.0a 60.9±6.6a 130.0±10.2b 67.9±3.5a* 69.7
±11.0b 181.6±10.7a ‘Orlando’ tangelo ‘Flying Dragon’ 38.2±3.5a 61.6±3.9a 156.7±4.6a 44.3±16.1b 71.6±15.3b 166.7±21.5a ‘Morton’ citrange – 18.4±6.2b 59.2±9.9a 169.8±12.5a 80.5±5.9a* 83.1±7.4a 194.5±15.6a ‘Morton’ citrange ‘Flying Dragon’ 21.5±4.7b 61.3±5.7a 154.0±7.9a 60.3±5.9a* 64.9±3.1b 171.4±9.5a ‘Carrizo’ citrange tetraploid – 5.1±1.0c 24.3±1.4b 73.9±14.3d 44.8±0.9b* 41.9
±0.3c 131.8±5.3b ‘Troyer’ citrange tetraploid – 14.1±4.8b 41.4±6.2b 85.8±9.2c 40.4±1.3b* 63.8
±5.3b 147.0±21.9b ‘Swingle’ citrumelo – 22.5±6.7b 35.6±10.9b 116.5±17.3b 58.1±3.5a* 82.4
±11.9a 157.2±10.1b ‘Swingle’ citrumelo ‘Flying Dragon’ 16.5±1.0b 49.2±7.1a 131.3±25.8b 70.2±6.4a* 51.6
±4.4c 182.3±15.7a ‘Davis A’ trifoliate – 4.1±1.1c 33.5±9.0b 101.3±20.2c 23.6±2.0c* 37.9±5.9c 156.6±23.2b ‘Davis A’ trifoliate ‘Flying Dragon’ 13.1±2.9b 54.8±8.2a 114.7±12.6b 50.5±7.3c* 71.2±10.3b 165.3±18.7a ‘Flying Dragon’ trifoliate – 2.7±0.8c 14.8±2.1c 67.3±9.8d 18.5±2.1c* 29.1±5.7c 59.6±2.7c ‘SFS’ sour orange – 0.13±0.1c 6.4±1.5c 51.5±14.8d 3.7±0.2d 19.5±3.0c 54.1±5.1c
Mean 19.4 47.4 114.8 48.3 63.0 147.2
CV (%) 22.81 15.54 13.44 12.71 13.01 9.39
Contrast
Non-interstocked plants 20.6 49.3b 127.3 55.7 73.1 171.8
Interstocked plants 21.5 61.0a 131.0 55.4 73.7 166.6
Interaction Rootstocks×Irrigation in fourth (P< 0.0001), fifth (P= 0.3397) and sixth (P= 0.2025) years. Means followed by different letters in columns are significantly different (P< 0.05) by Scott Knott’s test. Values represent means±SE.
Table 3
Cumulative fruit yield (second to fourth years and second to sixth years after planting) and yield efficiency of ‘Tahiti’ lime on different rootstocks, interstocked or not, under irrigated and non-irrigated conditions. Brazil, 2009.
Rootstocks Interstock Non-irrigated experiment Irrigated experiment
Cumulative yield 2–4 years (kg tree−1)
Cumulative yield 2–6 years (kg tree−1)
Yield efficiencya (kg m−3)
Cumulative yield 2–4 years (kg tree−1)
Cumulative yield 2–6 years (kg tree−1)
Yield efficiency (kg m−3)
‘Rangpur’ lime – 17.3±3.6b 166.6±11.1c 4.1±0.51b 55.0±1.4b* 228.8±9.7b 3.0±0.27b Catania 2 ‘Volkamer’ lemon – 60.7±9.7a 251.1±20.0a 3.9±0.38b 72.1±6.4b 339.8±10.0a 3.6±0.04b Catania 2 ‘Volkamer’ lemon ‘Flying Dragon’ 50.6±8.8a 253.5±19.6a 4.3±0.43b 61.7±2.5b 316.1±25.1a 3.3±0.34b ‘1646’ citradia – 38.8±2.8a 236.5±14.3a 4.6±0.63b 77.3±14.6a* 290.8
±24.4a 4.3±0.29a ‘1708’ citradia – 45.2±2.7a 236.0±17.4a 4.6±0.36b 76.7±5.4a* 328.0
±16.3a 5.2±0.45a ‘Orlando’ tangelo ‘Flying Dragon’ 48.6±5.5a 266.9±5.2a 3.9±0.08b 56.4±20.6b 294.7±56.0a 3.6±0.39b ‘Morton’ citrange – 31.7±5.2a 260.7±20.3a 4.9±0.49b 96.8±7.5a* 374.4±22.9a 4.2±0.42a ‘Morton’ citrange ‘Flying Dragon’ 38.4±6.6a 253.6±15.7a 4.2±0.10b 87.4±7.7a* 323.7±16.7a 3.3±0.18b ‘Carrizo’ citrange tetraploid – 16.2±4.5b 114.4±17.3d 2.8±0.46b 58.0±4.0b* 231.6±8.1b 3.5±0.11b ‘Troyer’ citrange tetraploid – 19.8±8.7b 146.6±23.4c 3.3±0.38b 51.7±5.5b* 262.4
±28.1b 4.1±0.63a ‘Swingle’ citrumelo – 32.7±5.9a 184.8±33.8b 3.4±0.22b 64.5±1.9b* 304.1
±18.7a 3.9±0.14a ‘Swingle’ citrumelo ‘Flying Dragon’ 27.8±5.1b 208.2±36.8b 4.5±0.84b 88.3±7.8a* 322.1
±21.5a 4.8±0.18a ‘Davis A’ trifoliate – 9.2±2.9b 143.9±27.7c 4.1±0.46b 34.7±2.9c* 229.3
±23.7b 4.6±0.12a ‘Davis A’ trifoliate ‘Flying Dragon’ 22.7±3.5b 192.2±23.2b 4.2±0.43b 69.9±11.1b* 306.5±36.6a 4.9±0.53a ‘Flying Dragon’ trifoliate – 9.3±0.7b 91.3±9.7d 8.4±0.40a 30.2±1.3c* 119.0±4.6c 4.4±0.31a* ‘SFS’ sour Orange – 0.1±0.1b 58.1±15.7d 3.6±0.97b 6.2±0.9d 79.8±3.4c 2.5±0.18b
Mean 29.31 191.5 4.31 61.69 271.9 3.94
CV (%) 37.23 17.83 11.24 27.23 22.4 6.8
Contrast
Non-interstocked plants 33.55 210. 1 4.08 67.04 311.89 4.05
Interstocked plants 34.86 226.9 4.3 76.82 317.1 4.06
Interaction Rootstocks×Irrigation in cumulative yield 2–4 years (P= 0.0003), cumulative yield 2–6 years (P= 0.3217) and yield efficiency (P= 0.003). Means followed by different letters in columns are significantly different (P< 0.05) by Scott Knott’s test. Values represent means±SE.
aYield efficiency was calculated from the relationship between fruit yield (kg tree−1) and canopy volume (m−3). * P< 0.05, rootstock differs between irrigated and non-irrigated experiments.
and ‘Valencia’ sweet oranges, ‘Redblush’ grapefruit and ‘Murcott’
tangor because the plants are too small and low yielding (Rabe,
1996; Wheaton et al., 1991). In Japan and the United States, ‘Flying Dragon’ trifoliate is used as a rootstock for ‘Satsuma’ mandarins in
greenhouse crops (Nesbitt et al., 2008). The mechanism by which
rootstocks, such as ‘Flying Dragon’ trifoliate, induce growth
reduc-tion on grafted plants is still unknown (Solari and DeJong, 2006).
The effect of ‘Flying Dragon’ as an interstock on vegetative growth and fruit production was influenced by the rootstock. It was observed that on the Catania 2 ‘Volkamer’ lemon rootstock, the interstock reduced plant size, while on the ‘Davis A’ trifoliate, it increased plant size. The use of ‘Flying Dragon’ trifoliate interstock also caused differences in vegetative growth on different roots-tocks in ‘Star Ruby’ grapefruit and ‘Michal’ and ‘Nova’ mandarins (Ashkenazi et al., 1992). On the other hand, ‘Morton’ citrange and ‘Swingle’ citrumelo seem to mask the effects of ‘Flying Dragon’ interstock and did not show significant differences in vegetative growth between plants with and without interstock. Other resear-chers have reported that ‘Volkamer’ lemon and ‘Carrizo’ citrange neutralized the effect of ‘Flying Dragon’ interstock on ‘Hamlin’
sweet orange plants (Ferguson and Chaparro, 2004). Regarding
cumulative yield, the rootstocks best suited to ‘Tahiti’ lime scion were Catania 2 ‘Volkamer’ lemon, ‘1646’ and ‘1708’ citradias, ‘Orlando’ tangelo, and ‘Morton’ citrange. Most of these rootstocks were classified as highly invigorating rootstocks, except on the citradias, which induced only intermediary vigor. Vigorous plants are grown in smaller densities at lower planting costs, but their high heights make pesticide applications and harvest labors difficult; thus, increasing operating costs. Less invigorating rootstocks have higher planting costs, but lower operating costs. Harvesting costs
of dwarf plants are lower by avoiding the use of ladders (Tucker
et al., 1994).
Irrigation increased vegetative growth and fruit production. These results support previous research regarding the close rela-tionship between the vegetative growth of young citrus plants and
the irrigation regime (Shalhevet and Levy, 1990). Likewise,
irriga-ted plants began to bear fruit earlier than plants without irrigation. Early-bearing is a highly valued attribute, especially in high density groves increasingly exposed to new phytosanitary problems
rai-sed in the last decade (Castle et al., 2010). Larger plants, however,
resulted in lower production efficiency in the irrigated experiment,
a fact that has also been observed on apples (Webster, 2004) and
on mandarins (Mourão Filho et al., 2007).
Based on their general performance, the evaluated rootstocks were classified according to their suitability for growth under irri-gated or non-irriirri-gated conditions. For non-irriirri-gated groves, the most appropriate rootstocks were the ‘Rangpur’ lime, Catania 2 ‘Volkamer’ lemon, the ‘1646’ and ‘1708’ citradias, ‘Morton’ citrange, and ‘Orlando’ tangelo. ‘Flying Dragon’ trifoliate also proved to be appropriate for non-irrigated conditions, although it is important to consider that in some seasons, the production on this rootstock
may drop dramatically because of drought stress (Stuchi and Silva,
2005). Moreover, high density planting of ‘Flying Dragon’ may lead
to higher planting costs. Another important criterion for rootstock
selection is their behavior concerning root rot caused by
Phytopht-horaspp. In this study, several trees on ‘Rangpur’ lime, ‘Volkamer’
lemon, ‘Orlando’ tangelo and ‘SFS’ sour orange were lost due to root rot.
The most suitable rootstocks for the irrigated plants were ‘1708’ citradia, ‘Morton’ citrange (not interstocked), ‘Swingle’ citrumelo (interstocked) and ‘Davis A’ trifoliate (interstocked). In general, irri-gation also increased the yield in plants grafted on intermediate invigorating rootstocks and their cultivation should be considered only under this condition. On the other hand, irrigated trees bud-ded on highly invigorating rootstocks did not significantly increase their yield. Irrigation increased plant vegetative growth, leading to a reduction in light interception and an increase in shading between trees that ultimately resulted in yields that were similar to non-irrigated plants. This information contradicts recommendations from other producing regions, such as Florida, where irrigation is an indispensable practice, even with an annual rainfall of about
irriga-tion is crucial because the critical periods of flowering and fruit set occur during the dry season. In Brazil, these critical periods coincide with the onset of rain. However, in the São Paulo State, strong droughts and dry periods do frequently occur during flo-wering and initial fruit set stages, causing intense drop of flowers
and developing fruits (Cantuarias-Avilés et al., 2010; Hutton et al.,
2007).
‘Rangpur’ lime induced higher yield when grown without irri-gation. Irrigation increased vegetative growth and, consequently, decreased plant density. These results may explain, in part, the extensive choice of ‘Rangpur’ lime in Brazil as rootstock for non-irrigated groves. However, this rootstock is very susceptible to root
rot caused byPhytophthoraspp. (Castle et al., 1993; Stenzel and
Neves, 2004). Therefore, its use in recent years has decreased in
Brazilian nurseries in favor ofP. trifoliatahybrids (Pompeu and
Blumer, 2006). In both experiments, plants budded on ‘SFS’ sour orange and ‘Orlando’ tangelo were the most susceptible to root rot, which caused the elimination of two treatments. Therefore, the use of both rootstocks is not recommended for ‘Tahiti’ lime. These results are supported by studies showing that ‘Orlando’ tangelo induces large plants and high yield, but it is highly susceptible to
root rot (Figueiredo et al., 1996). The ‘1708’ citradia outstood among
all the studied rootstocks by inducing high yield, both on irriga-ted and non-irrigairriga-ted conditions. Plants on this rootstock were intermediate-sized, with good quality fruit and had no symptoms of root rot susceptibility. The main criteria used in this study to select the rootstocks were yield, early-bearing, fruit quality, vigor, compatibility and tolerance to biotic and abiotic stresses. Howe-ver, these criteria are insufficient if not coupled with economical
aspects (Castle et al., 2010). In ‘Tahiti’ lime, for instance, higher
pri-ces are paid for large dark-green fruits destined for export or for
fruits picked in the off season (Gayet and Salvo Filho, 2003).
5. Conclusions
- ‘Flying Dragon’ trifoliate is a suitable rootstock for irrigated high density ‘Tahiti’ lime groves.
- The effect of rootstock on plant size and fruit yield can vary accor-ding to use of interstock. The ‘Flying Dragon’ trifoliate used as interstock increases the yield of ‘Tahiti’ lime grafted onto ‘Davis A’ trifoliate and ‘Swingle’ citrumelo, but reduces the yield of plants budded on ‘Morton’ citrange.
- Invigorating rootstocks grown without irrigation have high yields, with the ‘1646’ citradia and the ‘Morton’ citrange being strongly recommended for such conditions.
- The rootstocks tetraploid ‘Carrizo’ and ‘Troyer’ citranges, ‘Swin-gle’ citrumelo, and the trifoliates ‘Davis A’ and ‘Flying Dragon’ induced higher yields under irrigated conditions.
- The ‘1708’ citradia can be used as rootstock for irrigated or non-irrigated ‘Tahiti’ lime, inducing high yields in both conditions.
Acknowledgements
The authors acknowledge Fundac¸ão de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for the Ph.D. student fellowship to the
first author (Proc. 07/00286-0) and grant support to this research. The authors also acknowledge Mr. Luiz Gustavo Parolin and Mr. Dimas Alves Toledo for technical support, and Dr. Jay L. Schell for critical comments.
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