Climbing and Columnar Cacti: New Arid Land Fruit Crops

Reprinted from: Perspectives on new crops and new uses. 1999. J. Janick (ed.), ASHS Press, Alexandria, VA. Climbing and Columnar Cacti: New Arid Land Fruit Crops

Yosef Mizrahi and Avinoam Nerd* In Israel, scarcity of water, high input prices, and market competition limit the number of orchard crops that can be grown profitably. Our approach to the further development of the horticultural industry in the dry regions of Israel—the Negev and Judean deserts—is thus to establish new crops that will demand high prices in the export markets (Mizrahi and Nerd 1996). To this end, about 40 species of rare or wild fruit trees were introduced by us into these dry regions in a number of locations that differed in terms of soil, water, and climate (Nerd et al. 1990; Mizrahi and Nerd 1996). Emphasis was placed on candidates of the Cactaceae because of their high water-use efficiency (5–10 times higher than that of most conventional crops), resulting in low water requirement (Nobel 1988, 1994). The high water-use efficiency of cacti is provided by their unique photosynthetic pathway—crassulacean acid metabolism (CAM). In CAM plants, the stomata open

and CO2 uptake takes place during the night when evaporation is low. Among the Cactaceae, there are about 35 species that have a potential for cultivation as fruit, vegetable, or forage crop species (Nobel 1994; Mizrahi et al. 1997). Starting in 1984, we have introduced, for investigation as potential crop species, 17 members of the subfamily Cactoidae (Nerd et al. 1990; Mizrahi and Nerd 1996). Among these, four climbing (epiphytic) species and one columnar species have already been planted as commercial crops, and their fruits are being exported successfully to European markets as exotic fruits from Israel. The main reasons that these crops have made their way onto the market within so short a time after introduction are their precocious early yielding (three to four years after seeding or one to three years after propagation from cuttings) and their accept- ability in the markets. At present, our studies are aimed at examining the environmental adaptations of the species and their reproductive biology mode and at developing appropriate agrotechnological practices. In addition, a breeding program accompanied by cytological and molecular studies is being carried out in order to develop improved clones for cultivation. This review is divided into two parts. The first part deals with the climbing cacti of the genera Selenicereus and Hylocereus and the other with the columnar cactus Cereus peruvianus.

CLIMBING (EPIPHYTIC) CACTI

Taxonomy We collected wild or cultivated types of climbing cacti from a variety of sources—amateur cactus lovers, growers, botanical gardens, and backyards. We very soon realized that there is tremendous confusion about the taxonomic identity of these cacti: accessions with the same name were found to be of different species. We are currently applying cytological and molecular techniques to determine the proper taxonomic identities of the species that we have introduced (Lichtenzveig 1997). These species belong to at least to two different genera, Selenicereus and Hylocereus. From the genus Selenicereus we will elaborate here only on one species S. megalanthus, currently grown in Israel and in Colombia, where it is known as yellow pitaya (Hunt 1989; Barthlott and Hunt 1993), Acces- sions of S. megalanthus were introduced by us as H. triangularis or H. undatus and were later classified as S. megalanthus (Weiss et al. 1995; Mizrahi et al. 1997). We have 37 selected clones from this species. From the genus Hylocereus, we have introduced the following species, some with a number of clones (Table 1): H. undatus, H. polyrhizus, H. purpusii, H. ocamponis, and H. costaricensis (Britton and Rose 1963; Barthlott and Hunt 1993). In addition, we have introduced some promising unidentified clones of Hylocereus (Hylocereus sp.), the best of which was designated as 10487. Of these species, only the ones that are currently being grown in Israel for export are described in this paper, as follows: H. undatus, H. polyrhizus, and Hylocereus

*The authors thank the Fleischer Foundation and Harry-Stern & Hellen-Zoref Fund for Applied Research at BGU, for supporting this program. Special thanks to Mrs. Inez Mureinik for editing the manuscript.

358 sp. The later two species are not cultivated any where else in the world to the best of our knowledge. Some of these and other species are grown elsewhere: H. costaricensis, ( several commercial clones) as grown in Nica- ragua (known as red pitaya); H. undatus, in Mexico (known as pitahaya), in other Latin American countries (known as pitaya), in Vietnam (known as dragon pearl fruit or thang loy) (Mizrahi et al. 1997), and according to colleagues there, in Guatemala.

Horticulture At the beginning of our program, there was very little information available in the scientific literature on cultivation and biological background of these cacti. This information was mainly in Spanish in the form of hard-to-get dissertations and professional brochures (Mizrahi et al. 1997). We thus set out to investigate both horticultural and physiological aspects of climbing cacti and the results of our studies have been published in the professional literature, as follows: reproductive biology (Weiss et al. 1991, 1994a,b; Nerd and Mizrahi 1997), shading requirements (Raveh et al. 1993, 1996, 1998), and fruit development, ripening, and post-harvest handling (Nerd and Mizrahi 1998, 1999). Here, we will summarize some of the results and give details of new unpublished data to provide an up-to-date picture of the state-of-the-art know-how and marketing. Light tolerance. The climbing cacti originate in shady habitats of subtropical and tropical America. In Israel, the canopy suffers from bleaching and die back when these species are grown outdoors as a result of the intensive irradiation (noon photosynthetic photon flux densities can reach as much as 2200 mmol photons m-2 s-1). Our studies showed that for optimal development they have to be planted in nethouses and the required shade level (ranging between 30–60%) depends on the particular species as well as on the location (Fig. 1) (Raveh et al. 1996, 1998). H. polyrhizus and H. costaricensis are the most light tolerant, probably because of their unique skin characteristics (a wax cover and a thick skin). The radiation stress is exacerbated by high temperatures, as discussed below. Temperature tolerance. Sub-freezing temperatures damage the climbing cacti, and for most species 0°C is the minimal threshold for cultivation. Among the investigated species, Hylocereus sp. (10487) was the most sensitive to low temperatures and suffered cold injury when the temperature fell below 4°C. In the areas of the Negev with low night temperatures, the climbing cacti have to be cultivated in plastic- or glass-houses. Symptoms of cold injury are round lesions that expand along the stems. Plants recover easily when temperature increases. Our long-term observations showed that in the hottest parts of the Negev (Arava and Jordan valleys), where extreme summer temperatures (Fig. 3, 4) may rise up to 45°C, (average 39°C), annual flower produc-

40 Plastic only 30 +Net

10 Shoot damage (m) 0 H. polyrhizus H. undatus H. sp. (10487) Species Fig. 2. Heat and radiation damage to three Hylocereus species growing in a greenhouse in Beer-Sheva in the summer of 1998. The damage was estimated as the length (m) of stem that was liquefied along the trellis system. The net provided over 60% shade. Selenicereus megalanthus was not damaged by the high temperature. The Fig. 1. Cactus grown in a nethouse. numbers are averages per plant ± SE.

359 tion was very low, being about 15–20% of that obtained in areas with more moderate temperatures (where the average summer temperatures are lower by approximately 7°C). The timing of flowering was also affected by temperature. In areas with more moderate temperatures, flushes of flowers appeared in Hylocereus species from May to November and in S. megalanthus from September to December. Table 1. Species of the crawling cacti Hylocereus and In the hotter areas, flowering of both gen- Selenicereus introduced by Ben-Gurion University of the era was restricted mainly to the cool sea- Negev sons, May and Oct./Nov. for Hylocereus species and Nov./Dec. for S. megalanthus. No. of clones In physical terms, H. undatus showed the Grown greatest sensitivity to the extremely high Species Introduced commercially temperatures of the hot valleys: segments of stems at the surface of the shrubs turned H. costaricensis (Weber) 1 brown and became liquefied. The spell of Britton & Rose unusually high temperatures during the past H. ocamponis (Salm-Dyck) 1 summer in Beer-Sheva (4–5°C above the Britton & Rose multiannual average) (Fig. 3, 4) resulted in H. polyrhizus Weber 7 2 extensive damage to H. undatus, but very H. purpusii Weingart 1 small to the other species and nil to Hylocereus sp. 8 2 Selenicereus megalanthus (Fig 2). The H. undatus (Haworth) 27 3 damage becomes more intensive when Briton & Rose combined with high light radiation (Fig 2). S. megalanthus (Schum.) 37 6 Raveh et al. (1995) also reported physi- Britton & Rose ological damage to Hylocereus undatus Total 82 13 when grown under 35/45°C night/day temperature regime. The results of these stud- Outdoor Greenhouse-Beer Sheva ies indicate that these climbing cacti should 40 40 not be planted in extremely hot areas. H. Maximum Maximum undatus should be avoided, others may be manipulated with different shading regimes 30 30 and/or other agrotechniques, the feasibil- 20 20 ity of which should be tested. Minimum Reproductive biology. Studies on the Minimum

Average temp (˚C) 10 10 reproductive biology of these cacti, includ- Qetura 1998 ing the work of Weiss et al. (1994a,b) on Beer Sheva 1997 0 0 flowering and pollination, have previously 50 Maximum 50 been reviewed by us (Nerd and Mizrahi Maximum 1997). The results may be summarized as 40 40 follows: Flowers are nocturnal and open only once. All species, with the exception 30 30 of S. megalanthus, are self-incompatible 20 20 and thus require cross pollination. Due to Minimum Minimum a lack of local pollinators in Israel, hand Extreme temp (˚C) 10 10 pollination is necessary to obtain fruits; this factor results in a tremendous increase in 0 0 123456789101112 123456789101112 labor costs for the producers. All tested species were able to pollinate each other, Month and some pollinators produced bigger fruits Fig. 3. Average and extreme maximum and minimum outdoor than others. The fruits develop from both temperatures in Beer-Sheva and Qetura 1994–1997 and green- the ovary (pulp) and the receptacle that sur- house temperatures in Beer-Sheva for 1997 and 1998.

360 rounds the ovary (peel). The weight of the fruit correlates with the number of seeds (Weiss et al. 1994; Nerd and Mizrahi 1997), and with proper pollination the weight of Hylocereus fruits can reach about 800 g and that of S. megalanthus fruits, about 350 g. The Hylocereus species flower in waves, each Outdoor Greenhouse-Beer Sheva 42 42 wave lasting about one week, and hence Qetura Beer Sheva ripening also occurs in waves. The num- 39 39 ber of waves varies among the genera species and clones—from one to eight per 36 36 season. This characteristic creates mar- 33 33 keting problems: the fruits are available 1998 on the markets in short waves, whereas the Average temp (˚C) 30 1997 30 buyers want them spread out evenly over longer periods. Some species produce 50 50 flowers continuously, and hence fruits are 46 46 available throughout the season from June to December (Fig. 5–7), which is highly 42 42 desirable for the fresh-fruit market. We have already produced hybrids between 38 38 this continuously flowering species Extreme temp (˚C) (Hylocereus sp. clone 10487) and others 34 34 678910678910 with two- three waves of flowering (e.g., H. undatus clone 88-027), but these hy- Month brids have not yet started to flower. Stud- Fig. 4. Average and extreme maximum outdoor temperatures dur- ies are underway in an attempt to solve ing the hot summer months in Beer-Sheva and Qetura 1994–1997 this problem. All clones of S. and greenhouse temperatures in Beer-Sheva for 1997 and 1998. megalanthus are tetraploids; they flower 1996 1997 mainly in the autumn, and they are self- 25 H.undatus (88-027) H.undatus (88-027) 25 compatible (Weiss et al. 1994; 20 Total 17 flowers Total 68 flowers 20 Lichtenzveig 1997). The time elapsing 15 15 between flowering and ripening is about 30 days for the Hylocereus species, and 10 10 that for and S. megalanthus is 90 and 180 5 5 days for the early (late Sept.) and late 0 0 25 25 flowers (late Nov.), respectively (Nerd and H.undatus (89-026) H.undatus (89-026) Mizrahi 1998). This means that ripe fruits 20 Total 53 flowers Total 74 flowers 20 of the Hylocereus species may be ready 15 15 for marketing from late May to early Jan. 10 10 while those of S. megalanthus are available from Jan. to mid-May. 5 5

Fruit ripening and post-harvest be- Flowers per plant 0 0 25 25 havior. Some ripening characteristics H.undatus (89-024) H.undatus (89-024) Total 23 flowers Total 46 flowers have already been determined for a num- 20 20 ber of species, but studies on ripening and 15 15 post-harvest behavior are still under way 10 10 (Nerd and Mizrahi 1998, 1999). In gen- eral, the fruits are non-climacteric and are 5 5 0 0 sensitive to chilling injury. They may be May Jun. Jul. Aug. Sep. Oct. Nov. May Jun. Jul. Aug. Sep. Oct. Nov. stored for 10 days at room temperature if the proper maturation stage had been Fig. 5. Flowering waves of three clones of Hylocereus undatus reached before harvest. during 1996 and 1997. The numbers are flowers per week.

361 Irrigation and fertilization. To date, no systematic research has been performed on irrigation and fertilization requirements. In the meantime, we recommend that the climbing cacti be irrigated with 150 mm water/ year and fertilized with 35 ppm N from 23N-7P-23K fertilizer. Some farmers 1996 1997 use their own formulas and may irrigate 15 H. polyrhizus (89-027) H. polyrhizus (89-027) 15 with as much as 250 mm/year. Some Total 46 flowers Total 42 flowers preliminary experiments have demon- 10 10 strated large differences among species in response to water regimes. In a re- 5 5 search project for undergraduate students in the Department of Life Sciences of Ben-Gurion University, Mr. A’ssa’el 0 0 15 H. polyrhizus (88-054) H. polyrhizus (88-054) 15 Ram found that H. polyrhizus exhibited Total 18 flowers Total 23 flowers the greatest tolerance to lack of irriga- 10 10 tion (drought treatments) and S. megalanthus the least, with H. undatus 5 5 falling between the two extremes. These per plant Flowers findings were paralleled by the tolerance of the three species to high photon flux 0 0 15 H. sp. (10-487) H. sp. (10-487) 15 densities (Raveh et al. 1996, 1998), the Total 25 flowers Total 47 flowers tolerance being related to the 10 10 xeromorphic traits of the species as follows: H. polyrhizus has wax layer over the “skin,” the stomata are sunk into the 5 5 epidermis, and the stem tissue contains 0 0 a considerable volume of parenchyma; May Jun. Jul. Aug. Sep. Oct. Nov. May Jun. Jul. Aug. Sep. Oct. Nov. H. undatus has similar characteristics but lacks the wax layer; and S. megalanthus Fig. 6. Flowering waves of two clones of Hylocereus polyrhizus has no parenchyma, no sunken stomata and clone 10487 of Hylocereus sp. during 1996 and 1997. The and no wax layer and is thus most sensi- numbers are flowers per week. tive to water deprivation. This “drought 1996 1997 experiment” was performed over a short 9 S. megalanthus (Ecuador clones) S. megalanthus (Ecuador clones) 9 period (three months in winter), and the Total 14 flowers Total 27 flowers findings should be confirmed in a long- 6 6 term experiment, since these three species of cactus are perennials. An understanding of the effect of water re- 3 3 gimes on fruiting and fruit quality is ob- viously of the utmost importance. 0 0 9 S. megalanthus (Colombia clones) S. megalanthus (Colombia clones) 9 Pests and diseases. To date, no sig- Total 25 flowers Total 25 flowers nificant problems of pests or diseases 6 6 have arisen. In areas with high relative per plant Flowers humidity during the day (around 65%), some black knot may develop on fruits 3 3 of H. polyrhizus, which excrete sugars (glucose, fructose, and sucrose) from the 0 0 scales at the fruit tip. Ants are occasion- Sep. Oct. Nov. Dec. Sep. Oct. Nov. Dec. ally found on the fruits, fruits buds, and stems (which also excrete sugars), but no Fig. 7. Number of flowers per week of Selenicereus megalanthus major damage has been found. during 1996 and 1997.

362 Commercialization and Marketing From the moment we started our R&D project of introducing rare or wild fruit species to the Negev, we were told by the agricultural establishment that we were “playing with botany” in a project that had no real agricultural value. By 1993, however, we felt that we had accumulated sufficient know-how to start commercial evaluation of both input and output and to test the market in both Israel and Europe. Most of the farmers, government R&D agencies and AGREXCO were not interested in our new fruit crops (AGREXCO is an agency owned by the government and the farmers unions, which handles the export, under the brand label “Carmel,” of more than 90% of Israel’s agricultural produce). However, we did find three farmers who were fortunately prepared to risk their money and invest time and effort to try these unique hitherto unknown crops. The first three orchards (around 0.4 ha each) were planted in three different ecozones in the autumn of 1993. Among these growers was small private Israeli firm, Tropigarden, which also was the first to sell these fruits in Eu- rope. Sellers of the fruits claim that it is the beauty of the fruits that sell them. In 1995, a few hundred fruits were sent to the local market and 400 kg were sold in Europe, both for prime prices. In 1996, 10 tonnes were sold mainly in Europe and some in the local market, again for prime prices. In 1997, about 25 tonnes were sold, mainly in Europe. In that year, AGREXCO eventually realized the potential of these fruits, and offered the farmers a few more shekels (at that time 3.2 shekels = 1$US) per box (5 kg) than Tropigarden and sold a few tonnes in Europe. This year (1998), the “giant” AGREXCO is competing with the small Tropigarden to market the fruit for export. A number of problems have yet to be solved before the fruit can be commercially merchandised. One of the more important problems is that of nomenclature. At present, AGREXCO and Tropigarden are selling the fruits under two different names. Tropigarden sells the fruit under the name “Eden,” with pitaya in small letters, while AGREXCO markets it under the name pitahaya, the Mexican term. As already mentioned, this fruit is also supplied to the world markets (Asia+Europe) from Vietnam under the name dragon fruit. We suggest that a different name be used for each species to prevent confusion on the market. In Israel, we market three species of Hylocereus under the same name—whether Eden or pitahaya—but specify red or white flesh on the box. Since these three species differ from each other in many characteristics, including taste, each should have its own name. In particular, we should avoid using the term pitaya, which is a common name for many genera and species of the Cactaceae (Pimienta–Barrios and Nobel 1994; Mizrahi et al. 1997) differ- ing from each other as do, for example, the rosaceae fruits such as peach, cherry, apple, nectarine, and plum. We should keep the name “yellow pitaya” for S. megalanthus, which has already been available for some years in Europe, and dragon fruit for the white-fleshed H. undatus. For all other species, we should find new names. Even H. polyrhizus and Hylocereus sp. 10487, which both have red flesh, are not identical in taste or pigmentation: the pigment in 10487 is betalain (like that in beet-root), while the more purple pigment of H. polyrhizus has not yet been identified. Other problems of introducing the new fruits to the market are “educating” the buying public and ensur- ing that the produce reaches the shops at the correct stage of ripening. For example, we have seen overripe fruits in the local markets without leaflets to explain the nature of the fruit and its nutritional value, or how to eat it and where to store it. The fact that such problems can hamper the introduction of a new product to the market has been confirmed by Ms. Frieda Caplan, who was instrumental in introducing kiwi fruit and many other exotics to the American market. There are also horticultural problems that are still to be solved. Ways have to be found to manipulate the cacti to flower throughout the season, rather than in two or three waves, leaving most of the season without fruits—a major hurdle to successful marketing. At present, the crop is pollinated by hand, both the extraction of pollen and the cross pollination process itself being laborious and expensive. The development of pollen storage techniques and the subsequent creation of a pollen bank would solve the problem of the lack of proper pollen during the flowering period. In some species, taste should be improved. The long-term effects of environmental conditions, including irrigation and fertilization, have not yet been studied. Nothing is known about pruning and shaping of the plants, and the trellis system requires optimization, since such systems are quite expensive, the currently used one costing $12,800/acre. Breeding is also an important issue and is probably an easily achievable aim, since all existing clones are simply wild types awaiting genetic manipulation.

363 THE COLUMNAR CACTUS, CEREUS PERUVIANUS

Origin and Taxonomy We introduced seven species of columnar cacti of three genera, Pachycereus, Stenocereus, and Cereus. Among these, C. peruvianus (Britton and Rose, 1963) appeared to be most promising in terms of its rapid growth and precocious early yielding (Nerd et al., 1993; Weiss et al., 1993). C. peruvianus is not known in the wild and is always found as a planted ornamental (Nerd and Mizrahi, 1997). Dr. Leiah Scheinvar, a cactus taxonomist from the National University of Mexico (UNAM), drew our attention to the similarity between this species and C. jamacaru, which is native to the north-east of Brazil. Dr. Scheinvar thought it likely that the two were identical, and our recent study in Brazil supported this idea. However, seedlings raised by us from seeds of C. jamacaru obtained from Brazil exhibited some morphological traits different from those of C. peruvianus (Fig. 8). Studies are now being performed by us to determine the relationship between the two species, since C. jamacaru may be an important candidate for domestication and/or for breeding C. peruvianus. The first accession of C. peruvianus seeds was sent to us from Camarillo (southern California) by Mr. Ron Kadish, who collected the seeds from private gardens. C. peruvianus has already attracted attention in the US as a potential fruit-crop. The species, known as apple cactus, is mentioned in the excellent book of the late J. Morton, entitled Fruits of Warm Climates (Morton 1987). However, to date, the only research and development on this species is that performed in Israel by our group (Mizrahi et al. 1997), as described below.

Horticulture We do not intend to reiterate our findings published in the literature, but rather to summarize them together with unpublished scientific observations and information contained in student dissertations (Nerd et al. 1993; Weiss et al. 1993, 1994a,b; Wang 1997). The plants are being grown outdoors in all the ecozones tested in our introduction program (Nerd et al. 1993; Weiss et al. 1993). C. peruvianus is a precocious yielder from an early age—three to five years from seeds and two to three years from cuttings. The flower is nocturnal, and since it is self-incompatible, requires cross pollination. Clones should be mixed together in the orchard to guarantee pollination and fruit set. Pollination is performed by the honey bee Aphis mellifera, which is active during the day-time in the early and late hours of the flower opening. Low temperatures of –6 to –7°C resulted in significant damage to the plants, and these temperatures can thus be considered as minimum low for cultivation. We did not notice any damage from temperatures as high as 45°C. Water use is low, being 150 mm/year, as expected from cacti. The species is sensitive to salinity particularly when Na and Cl are the main salinity ions. Higher than normal concentrations of Ca, Mg and sulfates cause long-term damage, which precludes cultivation of C. peruvianus under salinity of 4 dS/m. The effect of low salinity (2.5 dS/m) on this crop is currently being tested. Approximately 30 days elapse from anthesis to ripening. Fruits have to be harvested for marketing at the stage at which the peel becomes smooth and fully colored. Fruits harvested prior to this stage (a very common mistake) have an inferior taste and do not ripen properly in storage. The fruit is nonclimacteric and can be stored for 14 days provided that it is harvested at the proper stage of ripening (Wang 1997). Breeding is now in progress from seeds of known parents. We have several thousand seedlings in our orchards from which to select the future cultivars. Orchards for this species are much cheaper to establish and maintain than those for the crawling cacti described above. Need- less to say, the findings described above are only the beginning of the R&D required to bring this species to the stage at which it will be a fully Fig. 8. Cereus peruvianus and exploited crop. Cereus jamacaru.

364 Commercialization and Marketing From 350 seedlings, we have selected eight clones that seemed to us suitable for cultivation. They were planted in 1993 in two ecozones in the Negev, i.e., Qetura, which has a harsh hot climate with saline water of 4 dS/m, and in the Besor, with fresh water of 1 dS/m and moderate temperatures (Nerd et al. 1993). To date, the orchard at Qetura has not yielded significant quantities (probably due to salinity), although export has already started from the Besor region. In 1995, the first fruits were obtained in small quantities. In 1996, a significant yield was obtained, but the farmers did not harvest the fruit, because “nobody knows what is this fruit all about” and were about to uproot the “useless orchard.” Not until mid-Sept. (half way through the season), did the farmers realize the potential of the crop, after the first boxes had been sold by Mrs. Dovrat Schwab to local restaurants, expensive hotels and exotic shops. She sold the fruit for 32 shekels/kg and gave the farmers half the proceeds (at that time 3.0 shekels = 1$US). This convinced the farmers that the crop might indeed be worthwhile. In 1997, AGREXCO started to sell this fruit under the name Koubo (to avoid the name pitaya) in Europe, where it was accepted very well. In 1997, 4 t were sold, both in Europe and on the local market, with the demand far exceeding the available supply. In Europe, the fruit is marketed with an excellent leaflet, giving information about the fruit and its uses. In the local market, some growers provide the leaflet but others do not. We found fruits in the supermarkets that had been harvested well before they reached the proper maturity stage and without accompanying leaflets. This can hamper the promotion of this new fruit. We hope that the Fruit Growers Association will take over introduction of the fruit to the local market proper way in a way that will ensure market penetration. We are sure that the export market for which AGREXCO is promoting the fruit for the first time as real new crop, will give the proper return to farmers and encourage further planting.

SUMMARY AND CONCLUSIONS The Negev Desert is the only place in Israel in which further development of the agricultural industry is still possible. Due to market competition, very high input prices and scarcity of water, conventional crops cannot ensure the future of agricultural development in Israel. Against this background, a variety of wild and rare fruit tree species were introduced by our group into the Negev Desert in a number of locations that differ in their environmental conditions. Among these species, two cacti—one climbing and the other columnar— have already made their way on to the European market. Two genera of climbing cacti from tropical and subtropical shady habitats—Selenicereus and Hylocereus—were introduced and are being grown either in green- houses to prevent exposure to subfreezing temperatures or in shade-houses to prevent damage by high photon flux densities. These cacti are S. megalanthus (known in Colombia as yellow pitaya) and H. undatus, H. polyrhizus, and an unidentified species Hylocereus, all known as red pitayas. The fruit of the latter three species was sold, under the name of Eden fruit, in local Israeli markets and exported to Europe for the first time in 1996. Total yields exported were 10 and 25 t in 1996 and 1997, respectively, with the fruit command- ing the highest prices ever obtained from fruits exported from Israel. To enable efficient production, studies of all aspects of horticulture, including agromanagement and breeding, being carried out at Ben-Gurion Uni- versity. Cereus peruvianus, a columnar cactus grown outdoors, went through a similar process of domestication. This fruit was sold for the first time in Europe in 1997 under the name Koubo. The farm-gate-price of 4 US$/kg was far beyond that commanded by any common fruit crop exported from Israel. The names Eden and Koubo were given the new fruits to avoid the use of the name pitaya, which covers many species and genera. The success of these new fruits supports the hypothesis that new crops can serve as a remedy to the troubled Israeli export market and that a viable agricultural industry is indeed feasible under the harsh conditions of the Negev Desert.

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