Abstract
Dragon fruit (Hylocereus sp. and Selenicereus sp.), also referred to as pitahaya or pitaya, is a member of the Cactaceae family and native to the tropical forest regions of southern Mexico, Central America, and northern South America. Its fruit is becoming increasingly popular as consumers seek healthy and more diverse food products. The crop adapts to different ecological conditions ranging from very dry regions to wet ones receiving more than 3500 mm of rainfall per year. U.S. commercial production of dragon fruit occurs mainly in Florida, southern California, and Hawaii. As growers learn more about this crop and how productive it can be, the acreage planted is likely to increase. Twelve dragon fruit cultivars grown on an Oxisol soil were evaluated for 5 years under intensive management at Isabela, PR. There were significant differences in number and weight of fruit per hectare among years. Cultivars exhibited an increase in fruit number and yield from 2010 to 2013 and then leveled off or declined. There were significant differences among cultivars for number of fruit and yield per hectare. Cultivars N97-17 and N97-15 produced significantly more fruit averaging 74,908 fruit/ha. Significantly higher fruit yield was obtained by cultivars N97-17, N97-20, N97-22, and NOI-13 averaging 17,002 kg·ha−1. Cultivar Cosmic Charlie had the lowest fruit yield, averaging only 25.1 kg·ha−1. Individual fruit weight was significantly higher in cultivars N97-20 and NOI-13 with fruit weight averaging 346.3 g. Cultivars NOI-16, N97-18, and Cosmic Charlie had significantly higher fruit soluble solids than others, averaging 17.4%. Some of the cultivars used in this study have shown horticultural potential and may serve as new planting material for growers.
The demand for tropical fruit has increased significantly during the past decade as consumers seek healthy and more diverse food products (Altendorf, 2019; Produce Marketing Association, 2017). Dragon fruit (Hylocereus sp. and Selenicereus sp.), also known as pitahaya or pitaya, is a member of the Cactaceae family and native to the tropical forest regions of southern Mexico, Central America, and northern South America (Mizrahi et al., 1997). The fruit was practically unknown 20 years ago, but it occupies a growing niche in Europe’s exotic fruit market (Le Bellec et al., 2006). The crop adapts to different ecological conditions ranging from very dry regions to wet ones receiving more than 3500 mm of rainfall per year. Dragon fruit tolerates temperatures ranging from 12 to 40 °C. Stem and collar rots caused by Xanthomonas campestris are a major production constraint in Malaysia (Zainudin and Hafiz, 2010). U.S. commercial production of dragon fruit occurs mainly in Florida, southern California, and Hawaii. As growers learn more about this crop and how productive it can be, the acreage planted will increase significantly (Merten, 2003). Dragon fruit has a very high antiradical and antiproliferative activity, a characteristic that should help its marketability among health-conscious consumers (Le Bellec et al., 2006; Li-Chen et al., 2006; Luo et al., 2014; Vaillant et al., 2005).
There is considerable variation in fruit shape and size among cultivars, ranging from nearly round to oblong and weighing between 70 and 680 g per fruit. Dragon fruit plants produce hermaphroditic flowers but the presence of key pollinators at flowering time, usually at night, is of critical importance. Some cultivars are self-incompatible (Crane and Balerdi, 2005). The number of flowering flushes depends on the species: seven to eight for white-fleshed pitahaya [Hylocereus costaricensis (some cultivars have red flesh)] and five to six for costa rica pitahaya (Hylocereus undatus) there is a period of 3 to 4 weeks between flowering flushes (Le Bellec et al., 2006). Dragon fruit species can be easily propagated through cuttings, which produce fruit ≈1 year after planting. A trellis system for stem support is required for commercial production of dragon fruit. Plant spacing varies depending on the trellis system. Minimum distances of 1.5–3.0 m between plants and 1.5–5.0 m between rows have been used commercially (Ben-Asher et al., 2006; Thomson, 2002). The fruit is considered nonclimacteric and once harvested maintains its quality for 2 weeks when stored at 14 °C (Nerd et al., 1999). Fresh-cut pitahaya slices stored at 4 °C can maintain shelf life for ≈25 d and keep good sensorial acceptance (Vargas-Vargas et al., 2010).
There is limited information available on total area of dragon fruit production worldwide. The largest producer in the United States is Florida with ≈160 ha, followed by Hawaii (80 ha), and California (60 ha). Vietnam is the largest producer worldwide with ≈40,000 ha (Lobo et al., 2013). The average seasonal price is ≈$1.25/lb (Evans and Jordan, 2011), but the fruit is sold in local markets at a price as high as $5.99/lb. Depending on the U.S. market demand, wholesale price of a 10-lb carton of fruit can be $42 to $55 (IndexMundi, 2019). Estimated production of fully mature dragon fruit plants is ≈19,000 lb/acre. However, results from replicated field trials to evaluate cultivars are very limited. The objective of this study was to determine yield performance and fruit quality traits of 12 dragon fruit cultivars grown in Puerto Rico in an Oxisol soil.
Materials and methods
This study was conducted at the U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS) Research Farm in Isabela, PR. The soil type is a Coto clay: clayey, kaolinitic isohyperthermic Typic Hapludox. Soil samples were collected 1 month before planting by taking 10 borings at a depth of 0 to 25 cm from each of the projected cultivar rows. The soil had a pH in water and 0.01 M calcium chloride (1 soil:2 water) of 6.05 and 5.22, respectively. The chemical composition of the soil was: 9 mg·kg−1 ammonium-nitrogen (NH4-N), 11 mg·kg−1 nitrate-N (NO3-N), 4.3 mg·kg−1 phosphorous (P), 236.3 mg·kg−1 potassium (K), 670.4 mg·kg−1 calcium (Ca), 137.6 mg·kg−1 magnesium (Mg), 64.2 mg·kg−1 iron (Fe), 58.7 mg·kg−1 manganese (Mn), 2.7 mg·kg−1 zinc (Zn), and 2.1% organic carbon. Soil pH in water and 0.01 M calcium chloride (1 soil:2 water) were measured with a glass electrode. Phosphorus and exchangeable cations K, Ca, Mg, Fe, Mn, and Zn were extracted with Mehlich III solution (Amacher, 2007) and determined by inductively coupled plasma spectrometry (Sumner and Miller, 2007). Organic carbon was determined by the Walkley-Black chromic acid wet oxidation method (Nelson and Sommers, 2007). Soil NH4-N and NO3-N were determined by steam distillation (Mulvaney, 2007). The 92-year mean annual rainfall is 1649 mm and Class A pan evaporation is 1672 mm. Mean monthly maximum and minimum temperatures are 29.8 and 19.9 °C. Average total rainfall and maximum, minimum, and average temperatures during the experimental period were 1329 mm, 28.1 °C, 21.2 °C, and 24.7 °C, respectively.
Grown cuttings (cladodes) of cultivars NOI-13, NOI-14, NOI-16, N97-15, N97-17, N97-18, N97-20, N97-22, American Beauty, Cosmic Charlie, Halley’s Comet, and Purple Haze were transplanted to the field on 27 Aug. 2009 and were arranged in a randomized complete block design with five replications. “N” cultivars were introduced from the USDA-ARS Tropical Plant Genetic Resources and Disease Research Unit, Hilo, HI, and are selections made by C.Y. Yen, which were donated to the center. The other cultivars were acquired from Pine Island Nursery, Miami, FL, and shipped air freight to Puerto Rico. Within a replication, plots for each genotype contained three plants spaced 10 ft apart and 15 ft between adjacent rows, 290 plants/ha. Plants were supported by a “T” trellis support system with three plants planted per post. The experiment was surrounded by a guard row of two plants each of cultivars Alice, Bloody Mary, Dark Star, Vietnam, Delight, Makisupa, Red Jaina, David Bowie, and Seoul Kitchen. Supplemental irrigation was provided with spinner jets (model DXMAG368X; Maxijet, Dundee, FL) spaced 20 ft apart and providing 13.5 gal/h at 20 psi when the soil water tension at a depth of 12 inches exceeded 50 kPa. Representative fruit from each experimental cultivar are shown in Fig. 1. Fertilization was provided every 3 months using a 15N–2.2P–16.3K–1.8Mg commercial mixture at a rate of 80, 245, 325, and 360 kg·ha−1 from planting until Dec. 2011, Mar. 2011 to Mar. 2012, June 2012 to Sept. 2012, and Dec. 2012 to Dec. 2014, respectively. Herbicide (glyphosate) for weed control was applied only in strips within the planting row. Weeds between rows were controlled with a tractor mower.
Representative fruit of 11 dragon fruit cultivars grown in Puerto Rico. Cultivar Cosmic Charlie was not available for photographing because of very low production.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Representative fruit of 11 dragon fruit cultivars grown in Puerto Rico. Cultivar Cosmic Charlie was not available for photographing because of very low production.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Representative fruit of 11 dragon fruit cultivars grown in Puerto Rico. Cultivar Cosmic Charlie was not available for photographing because of very low production.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Harvests were initiated in Sept. 2010. At this time, plants were ≈12 months old and producing fruit for the first time. At each harvest, number and weight of fruit were recorded. Fruit were harvested at color break when they started to show a slight change in color on the skin (exocarp). Representative fruit totaling 10% of those harvested in each treatment were used to determine fruit length and diameter. Soluble solids readings (percent) were also recorded using a temperature-compensated digital refractometer (Pocket PAL-1; Atago, Tokyo, Japan) when the fruit ripened, ≈2 d after harvest. After the end of each harvest year, plants were pruned with machetes at ≈3 ft above the ground. This practice was necessary to prevent cladodes from reaching the soil as a result of vigorous growth. Analysis of variance was carried out using the GLM procedure of SAS (release 9.4 for Windows; SAS Institute, Cary, NC). After significant F test at P ≤ 0.05, mean separation was performed with Tukey’s honestly significant difference range test.
Results and discussion
Year, cultivar, and the year × cultivar interaction showed highly significant effects (P ≤ 0.01) on all fruit parameters measured in the study (Table 1). The only exception was total soluble solids, which did not show a significant year and year × cultivar effect.
Yield and fruit quality traits of 12 dragon fruit cultivars planted in Puerto Rico. Values are means of five replications and 5 years (2010–14).
Overall, cultivars exhibited an increase in fruit number and yield during the first 3 to 4 years of production. This response was expected as plants increased in age (Table 2); however, the magnitude of the response varied among cultivars as expected by the significant year × cultivar interaction (Table 1). Except for ‘American Beauty’, ‘Halley’s Comet’, and ‘Purple Haze’, most other cultivars peaked in production in 2013 [year 4 (Table 2)]. After 2013, cultivars had an average decline in production of 28% (Table 2). Most probably, the high fruit load in 2013 in some cultivars in conjunction with yearly pruning resulted in depletion of assimilates, which then may have been the reason for an “off-year” in 2014 as plants built up carbohydrate reserves. ‘N97-15’ and ‘N97-17’ were the only cultivars indicating high and relatively stable fruit production and yield from 2012 to the end of the experimental period.
Number and yield of fruit of 12 dragon fruit cultivars grown in Isabela, PR. Values are means of five replications (2010–14).
Cultivars N97-17 and N97-15 had the highest 5-year mean for number of fruit, with values being significantly higher than all the other cultivars (Table 2). Cultivar N97-17 had the highest number of fruit in 3 of the 5 years the experiment lasted. However, depending on year, these values were not significantly different from ‘NOI-14’, ‘N97-15’, ‘N97-18’, and ‘N97-22’. ‘Cosmic Charlie’ had the lowest 5-year mean for number of fruit and yield but values for this cultivar were not significantly different from American Beauty and Purple Haze. Kek Hoe (2017) in Malaysia evaluated three plant densities in pitahaya over a 4-year period. He used plant densities of 1361, 1556, and 1815 trellis plants/ha which over the 4 years averaged 43,333, 38,809, and 34,125 fruit/ha, respectively. These yield values are 34% to 48% lower than those obtained by the best two producers (‘N97-15’, ‘N97-17’) in this study during their first 4 years of production (Table 2). There was no statistical difference in the numbers of total fruit produced by the more traditional cultivars, American Beauty, Cosmic Charlie, and Purple Haze, averaging 3172 fruit/ha (Table 1). Overall, the months of higher fruit production were mid-August to mid-September, although ‘NOI-13’ and ‘NOI-14’ had some production in June and peaked in September. The least productive months were November to May (Fig. 2).
Monthly fruit production of 12 dragon fruit cultivars grown in Puerto Rico. Values are means of five replications and 5 years (2010–14); 1 fruit/ha = 0.4047 fruit/acre.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Monthly fruit production of 12 dragon fruit cultivars grown in Puerto Rico. Values are means of five replications and 5 years (2010–14); 1 fruit/ha = 0.4047 fruit/acre.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Monthly fruit production of 12 dragon fruit cultivars grown in Puerto Rico. Values are means of five replications and 5 years (2010–14); 1 fruit/ha = 0.4047 fruit/acre.
Citation: HortTechnology hortte 30, 6; 10.21273/HORTTECH04699-20
Significantly higher fruit yield was obtained by cultivars N97-17, N97-20, N97-22, and NOI-13 averaging 17,002 kg·ha−1 (Table 1). This value is 75% higher than the average yield of all cultivars used in this study or 178% higher than the other cultivar excluding these. Kek Hoe (2017) found significant yield differences when dragon fruit was planted at three plant densities ranging from 8699 to 11,575 kg·ha−1 when averaged over a 4-year period. Fewer fruit produced by low-yielding cultivars in this experiment, particularly Cosmic Charlie was the result of reduced flowering. Visual observations of ‘American Beauty’ indicated fewer number of fruit not only because of fewer production of flowers as compared with other cultivars, but also little fertilization in those plants that flowered. The lowest production of 25 cultivars evaluated in the U.S. Virgin Islands, was also found to be American Beauty and Cosmic Charlie (Montilla et al., 2014). Self-incompatibility represents a mechanism to prevent inbreeding (Silva and Goring, 2001) and is reported in several dragon fruit cultivars (Crane and Balerdi, 2005); however, Cosmic Charlie and American Beauty are reputed to be self-compatible (Growables, 2020). However, even if compatibility was an issue for these cultivars in this experiment, there were 11 other experimental and 9 border row cultivars available for cross pollination. The possibility of ‘Cosmic Charlie’ flowers opening at different times than others in this experiment is doubtful; however, close monitoring of flowering hours was not conducted as part of the study. Throughout the experimental period the presence of pollinators [bees (Anthophila), fruit flies (Drosophilidae), bats (Chiroptera)] was easily visible.
Individual weight of fruit averaged over cultivars was 211.9 g (Table 1). In Malaysia, fruit are classified into four grades based on fruit weight: grade “AA” for fruit weighing 500 to 800 g, grade “A” for 350 to 450 g, grade “B” for 250 to 350 g and grade “C” for fruit weighing less than 250 g (Zainudin and Hafiz, 2010). Under this grading criteria, only cultivar N97-20, with an individual fruit weight of 383.3 g, would meet grade “A.” However, individual fruit weight of this cultivar was not significantly different from that of NOI-13. Thinning fruit to one or two per stem may have resulted in an increase in fruit size and weight. However, this study sought to identify cultivars requiring minimum labor costs for dragon fruit production in California, Florida, Hawaii, and Puerto Rico where hourly labor cost is high. Hence, fruit thinning was not considered. To our knowledge, there are no grade guidelines for dragon fruit in the United States. In Florida, large dragon fruit producers sell their fruit in 10-lb boxes containing fruit of various sizes, but usually between 8 and 15 fruit per box. Jumbo boxes containing seven fruit or fewer per box are also sold (A. Monterroso, personal communication). Further, grading is mainly based on presence or absence of fruit defects. First-class fruit should be clean fruit with very minimum blemishes, scars, and spots (burns). Decay [anthracnose damage (Colletotrichum gloeosporoides), etc.] is not allowed in first-class fruit.
Significantly higher soluble solids concentration values were obtained from fruit of ‘NOI-16’, ‘Cosmic Charlie’, and ‘N97-18’, which averaged 17.4% (Table 1). This value was lower than that obtained by Mallik et al. (2018) in Bangladesh, who measured soluble solids concentration of two cultivars at 38 d after fruit set and obtained values from 21.9% to 27.2%. In a review article, Le Bellec et al. (2006) lists soluble solids concentration values for dragon fruit ranging from 7.1% to 10.7%. Nomura and Yonemoto (2005) studied the change in sugars and acids at various intervals after pollination and found soluble solids concentration in white-fleshed dragon fruit ranging from ≈13.7% to 18.0%, depending on where on the fruit the sample was taken.
Cultivar N97-20 produced longer fruit, but these were not significantly different from those of eight other cultivars (Table 1). Greater fruit diameter was obtained with ‘N97-22’; however, as with length, it did not differ significantly from several other cultivars used in the study (Table 1).
In conclusion, 12 dragon fruit cultivars were evaluated for the first time during 5 years of production. Cultivar N97-15 and N97-17 produced significantly more fruit. Higher yields were obtained by cultivar NOI-13, NOI-17, NOI-20, and N97-22. However, except for ‘NOI-13’, these cultivars produce fruit with white pulp (white-fleshed), which depending on market preference may command a lower price than red-fleshed cultivars, which are more attractive and have higher antioxidant activity.
Units
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