The Fig: Overview of an Ancient Ed Stover1 and Malli Aradhya USDA, ARS, National Clonal Germplasm Repository, One Shields Avenue, University of , Davis, CA 95616 Louise Ferguson and Carlos H. Crisosto Department of Sciences, One Shields Avenue, University of California, Davis, CA 95616 Additional index words. carica, biology, postharvest

The genus Ficus includes species ranging of the prophet Mohammed indicating, ‘‘If The female flowers in edible figs are long in number from 600 to more than 1900, with I could wish a fruit brought to paradise it styled and produce a much more succulent most found in the tropics or subtropics and would certainly be the fig’’ (Condit, 1947). It fruitlet, in contrast to female flowers in only a handful with considered edible is strange to think that this esteemed fruit is the short-styled monoecious wild-type figs (reviewed in Condit, 1969). The cultivated virtually unknown to most U.S. consumers, (Fig. 1, Armstrong, 2006). It is proposed fig, Ficus carica L., (), is clearly of except as a brown paste inside distinctive fig (Storey, 1975) that a mutation in the wild fig greatest importance as a source of human cookies. gave rise to the long-styled pistils/succulent food. The fig fruit has long been associated fruitlet in the edible fig (Table 1). As either a with horticulture in the Mediterranean region THE FIG pleiotropic effect or mutation in a tightly (Zohary and Spiegel-Roy, 1975) and is con- linked gene, the edible fig also displays a sidered to have been ‘‘first brought into cul- Fig are , fast growing, and suppression of the androecium. Some so- tivation in southern Arabia’’ (Storey, 1975). spreading in habit, so that they tend to be called caprifigs are reported to be edible and Wild or ‘‘nearly wild’’ figs are reported greater in width than in height. from have a more succulent fruitlet than typical throughout much of the and cuttings or seed typically grow into single- caprifigs. We do not know of any studies that Mediterranean region (De Candolle, 1886). trunk trees with little training, but trees investigate the anatomic or genetic factors Cultivated figs are reported to have become damaged by freeze or other injury, may that result in these so-called edible caprifigs. established across the Mediterranean region resprout from with multiple trunks. Four types of figs are described based 6000 years ago, reaching England by 500 The wood of fig trees is low in density and on cropping/pollination characteristics. The CE (Ferguson et al., 1990). Interestingly, the breaks easily. Branches have a pithy interior. type known as ‘‘common figs’’ requires no record shows a prehistoric distribution Latex, which is irritating to human skin, is pollination to set a commercial crop. Bota- of Ficus carica across southern produced from all broken plant structures. nists use the term ‘‘persistent’’ rather than (De Candolle, 1886). Tree height at maturity varies according ‘‘parthenocarpic,’’ because the fig is not a to genotype and typically ranges from 3 to true fruit. The other two types of edible fig FIG PRODUCTION WORLDWIDE 10 m. Fig trees are very plastic in form and are not persistent and require pollination to can be pruned to many shapes and remain set the main crop of figs. Botanically, these Fig is widely planted in door yards productive. nonpersistent types are classified as ‘‘caudu- throughout the Mediterranean region (and cous’’ and are classed as Smyrna types (e.g., similar climates), and is well adapted to STRUCTURE OF THE FIG FRUIT ‘Calimyrna’, ‘Marabout’, and ‘Zidi’) and San drought and high temperatures. The Food Pedro types (e.g., ‘Dauphine’, ‘King’, and ‘San and Agricultural Organization of the United The fig ‘‘fruit’’ is a composite formed of a Pedro’). The San Pedro types are distinguished Nations (FAO, 2006) estimates that figs are hollow shell of tissue enclosing by setting a persistent early crop, known as harvested from 427,000 ha, producing more hundreds of individual pedicellate drupelets than one million metric tons per year. that develop from the individual female flow- ‘‘breba’’ fruit, but require pollination (called ‘‘caprification’’ in figs) to set the main crop. produces 26% of the world’s figs and, when ers lining the receptacle wall, with a small combined with , , , , scale-lined opening (called the ostiole or eye) The fourth type, caprifigs ( figs), and , these top six producing coun- at the distal end. The tiny flowers and even provides the source of pollen for commercial tries account for 70% of the world’s annual the initial prosyconium are so small that figs plantings of cauducous figs. Fig pollen is production. The ranks eighth, were once considered to bear fruit without carried by a unique wasp ( with 4% of global fig production in 2005. ever forming flowers. This composite fruit is psenes L.), that has co-evolved with the fig. Fourteen U.S. states produce figs commer- called a ‘‘’’ (reviewed in Condit, (Kjellberg et al., 1987). An important botan- cially, but California produces 98% of the 1947). The mature fruit of the edible fig has a ical component of this co-evolution is the U.S. crop, on 5100 ha, but with a yield per somewhat tough skin, a whitish interior rind, protogynous nature of the caprifig, so that hectare three times the global average. and a sweet, gelatinous pulp comprised of the female flowers are receptive 6 to 8 weeks individual ripe drupelets. The seeds within before anthers mature in the same syconium APPRECIATION FOR FIGS the drupelets range from virtually nonexis- (Condit, 1932). Through this feature, wasps tent to subtly crunchy. enter, pollinate, and oviposit a syconium that Historical works provide evidence of the later has mature pollen as the next wasp sustained importance and appreciation of figs FIG POLLINATION BIOLOGY generation emerges. in the Mediterranean area. in AND ITS GENETIC BASIS The blastophagas develop in caprifigs, his Natural History (Bostock and Riley, 1855) which are kept separate from the figs to extolled ‘‘One hundred and eleven observa- In addition to having a distinctive fruit, maximize control of pollination. Ripe capri- tions’’ on the fig. Among them, ‘‘This fruit the fig also has an interesting and distinctive figs are cut and placed in bags or baskets in invigorates the young, and improves the pollination biology. Wild figs produce both trees of the Smyrna and San Pedro-type figs, health of the aged and retards the formation functional male and female flowers within the and are typically supplied at three times in of wrinkles,’’ and (revealing just one more syconium. Fruiting produce functional regular intervals in May through June in among many observations) ‘‘Mixed with female flowers with abortive hermaphroditic California. The fig growers goal is for only axle-grease it (fig milk) removes .’’ flowers ringing the ostiole (Beck and Lord, one wasp to enter each fig. Excessive polli- Among the most interesting comments is that 1988), but vary in their need for pollination. nation increases fruit splitting. In addition,

HORTSCIENCE VOL. 42(5) AUGUST 2007 1083 food safety concerns (Doster et al., 1996). In fig breeding, it has been easy to select good maternal parents, because they presumably exhibit the qualities that the breeder is likely pursuing. The strength of California fig breeding has been the focus of identifying and developing improved caprifigs, and cre- ating pollen parents that convey good fruit quality and the persistent trait, which elimi- nates the need for pollination. Key to this strategy was developing an understanding of the genetics of the persistent trait. Interest- ingly, it was found that the allele for persis- tence is dominant but is lethal in the , and thus can only be conferred by the pollen parent (Table 3) (Saleeb and Storey, 1975). When the genetics of persistence and long styles/suppressed androecium are both con- sidered, it becomes apparent that no more than 25% of the progeny will carry both of these traits.

BREBA CROP VERSUS MAIN CROP Fig. 1. Floral morphology in caprifigs and edible figs. (Figure used with permission, Armstrong, 2006) Although San Pedro types are in part defined by the setting of a breba crop, some Table 1. Percentage edible figs in progeny based on are as dried fruit. Reflecting this fact, 94% of common figs will also produce brebas. Bre- genotypes of pollen and seed parents (Storey, California fig production is dried or other- 1975). bas are the first figs of the , setting on wise processed. wood from the previous year, and typically Seed Parent Of the cultivars described by Condit mature in June in the Central Valley of Pollen parent GA/GA GA/ga (1955), 78% are common types, less than California. Some cultivars are grown because GA/GA 0% 0% 4% are San Pedro types, and the remaining of their tendency to produce brebas (which GA/ga 0% 25% 18% are Smyrna types. Cultivars also vary in tend to be larger than main crop figs), are ga/ga 0% 50% such traits as leaf morphology, plant vigor, relatively scarce on the market, and tend to G and A are closely linked loci. fruit external and internal color, fruit flavor/ get a high price as fresh fruit. The main crop G, dominant allele for short-styled pistils; g, reces- degree Brix/titratable acidity, seed character- sive allele for long-styled pistils; A, dominant is produced on the current season’s wood, istics, shape of fruit, skin thickness, ostiole maturing fruit from August through Novem- for functional androecium (and thus pollen); diameter, and duration of fruit production. a, recessive allele suppressing androecium. ber (in Winters, CA.) or even later in a warm A small selection of the amazing diversity in year. Achievement of maturity in main crop fig cultivars, focusing primarily on commer- fig fruits on a single tree is sequential, the incidence of internal defects incited by cial varieties, is described in Table 2. beginning with development of basal fruits microorganisms is increased with the inci- and progressing toward the most distal fruits. dence of wasp entry. BREEDING FOR IMPROVED FIGS This makes it necessary to harvest repeatedly in production of fresh fruits (Chessa, 1997), FIG CULTIVARS Virtually all fig cultivars did not arise whereas figs for drying are typically collected through a planned breeding program. Begin- from the ground in a single harvest for main Naming of desirable fig cultivars is ning in 1908, efforts at fig improvement were crop figs (Obenauf et al., 1978). recorded as early as the fourth century BCE. begun in California. This became a sustained In the first century ACE, Pliny lists 29 varieties focus at the University of California at CULTIVATION OF FIG of fig. De Candolle (1886) notes that the Riverside from 1928 to the 1980s by Ira ‘‘cultivated forms [of figs] are numberless.’’ Condit and William Storey. Doyle and Fer- Fig is especially well adapted to Mediter- Even after eliminating suspected synonyms, guson (1997) of the University of California ranean environments, with cool winters and the most complete fig monograph (Condit, at Davis just released the ‘Sierra’ fig for hot, dry summers, but can be grown in more 1955) describes 607 named fruit-producing drying and will soon release the ‘Sequoia’ humid regions, including the tropics and cultivars. fig, which is expected to find a place in fresh subtropics, where they will experience more However, the California fig industry is fig production. Other efforts are ongoing in fruit splitting and disease. A chilling require- largely based on five cultivars: Calimyrna the United States and other countries. ment to break dormancy is typically around (Sari Lop), Adriatic, Mission, Brown Turkey, The stated focus of the California fig- 300 h (California Rare Fruit Growers, 1996). and Kadota (California Fig Advisory Board, breeding effort has been development of Fig plants will survive as far north as New 2006; California Fresh Fig Growers Associ- ‘Calimyrna’-like quality without the need Jersey in protected areas such as south-facing ation, 2006). Fresh fig quality is greatest at for caprification and with a small ostiole walls of houses, and can tolerate temper- full ripeness, but such soft figs are especially (reviewed in Storey, 1975). This would elim- atures as low as –10 °C (California Rare Fruit sensitive to damage (Chessa, 1997). There- inate the expense and also the uncertainty Growers, 1996). Many cultivars require lots fore, the balance between quality and even a associated with the caprification process, of heat units to achieve good fruit quality and modest shelf-life demands harvest at early such as the potential for too little pollination, are never acceptable in cool climates like ripeness (good color) in fresh figs for com- excess pollination leading to splitting of coastal California (California Rare Fruit mercial sale. Even though most of world’s many fruits (Crane and Blondeau, 1949), Growers, pers. comm.). Commercial produc- figs are eaten fresh, their fragility has demanded increased incidence of internal damage from tion is concentrated in dry hot summer that fresh figs are largely consumed where pathogens introduced by blastophagas climates and fig is extremely drought tolerant they are produced. Because of their high (Michailides et al., 1996) or other vectors once established, but needs regular watering content and stability, most fig exports (Schwaez, 1933), and potential associated during establishment and achieves greater

1084 HORTSCIENCE VOL. 42(5) AUGUST 2007 H ORT S CIENCE V OL

25 A 42(5) . Table 2. Characteristics of selected fig cultivars. Pollination Breba crop Main crop Category Major synonym Region Size Skin Color Pulp Color Use Size Skin Color Pulp Color Use Flavor UGUST Adriatic Common Verdone California *z * * * Small to Green to Light pink Dried, fresh Mild , rich medium yellow–green to pink

2007 Alma Common Texas (home) * * * * Small Yellow Amber to pink Fresh, preserves Caramel Black Bursa Smyrna Bursa Siyahi Turkey na y na na na Large Striped violet– Red Dried, Fresh Berry-like, rich brown–green to purplish black Brown Turkey Common California, Israel, Very large Violet–brown Pink Fresh Very large Violet–brown Amber Fresh Mild caramel Global Celeste Common Malta? Southeast United na na na na Small to Violet bronze Amber to pink Fresh, preserves Caramel States (home) medium Conadria Common California Large Green with Light pink Fresh Medium Light Light pink Dried Honey purplish tint yellow–green Cuella Dama Common Col de Dame , Chile na na na na Medium Green Red Fresh Berry-like Blanco Dottato Common Kadota Italy, California, Medium Green to Amber to Fresh Medium Green to yellow Green to Canned, dried Honey Chile yellowish green pink yellow amber Kalomon Smyrna Kalamata Greece —x —x —x —x —x —x —x —x —x King San Pedro Desert King California Large Green Pink Fresh Medium to Greenish purple Amber to Fresh, dried Honey large light pink Lampiera San Pedro Large Greenish brown Rose Fresh —x —x —x —x —x Masui Dauphine Common? Masui Dolphin Japan Very large Violet–brown Pink Fresh Very large Violet–brown Pink Fresh Mild caramel to purple Mission Common Franciscana, California, Spain Large Purplish black Light pink Fresh Medium Purplish black Amber to Dried, Fresh Berry-like, rich Brebal light pink Panachee Common Striped tiger United States na na na na Medium Yellow with Dark pink Fresh Intense (home) green stripes to red raspberry, rich Sari Lop Smyrna Calimyrna, Lob Turkey, California na na na na Large Light yellow to Amber to Dried, fresh Caramel, rich Injir, Sarlop golden yellow light pink Sierra Common California na na na na Medium large Green to yellow Amber to Dried, fresh Caramel, rich light pink Sultani Common Fayoumi, Egypt, Medium large Green and Pink Fresh Medium large Violet–brown Light pink Dried, fresh Rich Ramadi brown Zidi Smyrna North Africa na na na na Very large Purplish black Pink to red Dried, fresh Berry-like, rich zBrebas are rare or nonexistent. yBrebas are reported not to be produced. xNo information available. na, not applicable. 1085 Table 3. Percentage persistent figs in progeny Earlier maturation and abscission of dried THE FUTURE based on genotypes of pollen and seed parents figs permits harvest before there is a signif- (Saleeb and Storey, 1975). icant risk of rain. Carefully timed Ethephon As a complement to the rich pleasures of Seed Parent applications may be used to help accelerate dried figs and their products, there is a great Pollen parent +/+ +/P this process (Morton, 1987). deal of interest in expanding fresh fig sales in +/+ 0% 50% the United States and around the world. This +/P 0% 50% PESTS AND DISEASES will require significant advances in posthar- +, wild-type allele for caducous syconia and vest handling. Based on our experience with normal ; P, dominant mutant allele for Nematodes in the genus Meloidogyne naive consumers, the potential customer base persistent syconia but lethal in ovule. may be the most important and widespread for fresh figs is very large. Visitors to the pest of fig (McBeth, 1949). Figs have few National Clonal Germplasm Repository in other routinely serious pests or diseases Davis, CA, are astounded by the bright fruity yields when irrigated. In irrigated orchards, except where rain is common in summer. flavors, reminiscent of or citrus, of water supply is reduced in the weeks before Even commercial fig orchards in California some fresh fig varieties. maturity for dried-fruit production, but is rarely receive pesticide sprays. Arthropod maintained for fresh production. Fig thrives pests are sporadically important and include Literature Cited on soils ranging from light sand to heavy clay dried-fruit pests like the coleopteran Carpo- or limestone (Morton, 1987). phillus hemipterous and lepidopteran Ephes- Armstrong, W.P. 2006. Sex determination & life Figs easily from cuttings and this is tia figulilella (reviewed in Ferguson et al., cycle of Ficus carica. Aug. 2006. . In Florida (Krezdorn and Glasgow, 1970) and splitting is common and fungicides may be Beck, N.G. and E.M. Lord. 1988. Breeding system in Ficus carica, the common fig. I. Floral the Philippines (De La Cruz and Gonzalez, necessary to control Alternaria, Aspergillus, diversity. Amer. J. Bot. 75:1904–1912. 1953), grafting F. carica to the rootstock of Botrytis, and Penicillium fungi (Tous and Bostock, J. and H.T. Riley (trans.). 1855. Pliny the other species has been demonstrated. Top- Ferguson, 1996). Elder: The natural history, Book 23, Chapter working trees to more desirable varieties can Alternaria and Fusarium are especially 63. Taylor and Francis, London. be done with a variety of budding and graft- noteworthy for producing internal fruit rot Buchanan, J.R., N.F. Sommer, and R.J. Fortlage. ing methods (Morton, 1987). In California and are the primary fungal concerns in 1975. Aspergillus flavus infection and aflatoxin there are unpublished reports of budding California fig production, whereas other dis- production in fig fruits. Appl. Microbiol. F. carica to different rootstocks of the same eases may be important in some orchards in 30:238–241. species for size control or manipulation of fruit individual years (reviewed in Ferguson et al., Chessa, I. 1997. Fig, p. 245–268. In: S. Mitra (ed.). Postharvest physiology and storage of tropical maturity (California fig growers, pers. comm.). 1990). Endosepsis, also called pink/brown/ and subtropical fruits. CAB International, New fig plantations are typically estab- soft/eye-end rot, is caused primarily by Wallingford, UK. lished after 12 to 15 months in the nursery F. moniliforme pv. Fici (Ferguson et al., California Fig Advisory Board. 2006. Varietal info. and will set some fruit the following year 1990), and formerly resulted in 30% to 50% Aug. 2006. . commercial production in 3 to 5 years. Fig 1928). The is maintained in consecu- California Fresh Fig Growers Association. 2006. orchards do not require regular fertilization tive fruit stages of caprifig trees and is and varieties. Aug. 2006. . cation will encourage plant growth at the wasps. This problem is a major reason for California Rare Fruit Growers. 1996. Fig. Aug. 2006. . expense of fruit production. No more than 0.2 the California shift away from varieties Condit, I.J. 1932. The structure and development of to 0.5 kg N should be applied per tree per requiring pollination. flowers in Ficus carica L. Hilgardia 6:443–481. year, with split applications from early spring Aflatoxin, a mycotoxin produced during Condit, I.J. 1941. Fig culture in California. Calif. through July (Morton, 1987). Nitrogen is the A. flavus infection, is sometimes detected in Agr. Ext. Serv. Circ. 77. Berkeley, CA. only nutrient that is regularly applied to fig dried figs. This compound is a potent carcin- Condit, I.J. 1947. The fig. Chronica Botanica Co. orchards. ogen and is subject to monitoring and product Waltham, MA. Orchards for dried-fig production in Cal- rejection at very low thresholds by the Condit, I.J. 1955. Fig varieties: A monograph. ifornia are typically planted in a wide spacing Food and Drug Administration. Infection is Hilgardia 23:323–538. (6–12 m between trees), receive pruning to thought to occur during sun-drying of figs Condit, I.J. 1969. Ficus: The exotic species. Uni- versity of California, Division of Agricultural sustain adequate annual growth, and figs are on trees, but despite the routine use of this Sciences. Berkeley, CA. harvested from the manicured orchard floor practice, aflatoxin incidence in figs is very Crane, J.C. and R. Blondeau. 1949. The use of after abscission (Ferguson et al., 1990). Figs low (Buchanan et al., 1975). Even though this growth-regulating chemicals to induce parthe- for fresh fruit production in California are problem is rare, detection and reducing for- nocarpic fruit in the Calimyrna fig. Plant topped to permit harvest with minimal ladder mation of mycotoxins in figs are active areas Physiol. 24:44–53. work, and are sometimes planted at much of research (e.g., Karaca and Sebahattin, De Candolle, A. 1886. Origin of cultivated plants higher densities, including trellising in a in press). (reprint of 2nd edition, 1967). Hafner Publish- ‘‘cordon’’ production system similar to that Worldwide, fig mosaic disease (FMD) is ing, New York. for grape (California fig growers, pers. a concern, producing typical mosaic virus De La Cruz, E. and L.G. Gonzalez. 1953. The graft affinity of the fig, Ficus carica, with some of its comm.). With aggressive management, this symptoms of yellow rings on leaves and congeners. Philipp. Agr. 37:119–129. cordon system can be used to produce two sometimes symptoms on fruit. Stunting of Doster, M.A., T.J. Michailides, and D.P. Morgan. main crops per year in regions with year- trees and reduced productivity are associated 1996. Aspergillus species and mycotoxins round warmth (Israeli fig growers, pers. with severe foliar symptoms (California fig in figs from California orchards. Plant Dis. comm.). When pruning figs, special care growers, pers. comm.). Although FMD is 80:484–489. must be taken if breba production is impor- believed to cause significant economic los- Doyle, J. and L. Ferguson. 1997. Breeding persis- tant, because these fruit grow on the previous ses, it is difficult to assess (Condit, 1941). The tent figs with Calimyrna quality. Acta Hort. season’s wood. causal agent of FMD has never been con- 480:259–264. Production of quality fresh figs outside the firmed, although it is likely a virus or com- FAO. 2006. FAOSTAT agricultural data. Aug. 2006. . peak harvest season results in premium pri- plex of viruses thought to be vectored by the Ferguson, L., T.J. Michailides, and H.H. Shorey. ces. For this reason, some growers manipu- mite Aceria ficus (Serrano et al., 2004). Use 1990. The California fig industry. Hort. Rev. late time of budbreak by timing pruning, of shoot-tip culture and thermotherapy (Amer. Soc. Hort. Sci.) 12:409–490. control of irrigation, and use of hydrogen reduce or eliminate symptoms (Gella et al., Hansen, H.N. 1928. Endosepsis and its control in cyanamide (e.g., Norberto et al., 2001). 1998). caprifigs. Phytopathology 18:931–938.

1086 HORTSCIENCE VOL. 42(5) AUGUST 2007 Gella, R., J.A. Marin, M.L. Corrales, and F. Michailides, T.J., D.P. Morgan, and K.V. Schwaez, O. 1933. Beitrage zur Pathologie der Toribio. 1998. Elimination of fig mosaic from Subbarao. 1996. An old disease still a Feige, Ficus carica ii. I. Das Frachtfaulepro- fig shoot-tip cultures by thermotherapy. Acta dilemma for California growers. Plant Dis. blem in Kleinasien. Phytopath. Zeitschr. Hort. 480:173–177. 80:828–841. 6:589–618. Karaca, H. and N. Sebahattin. (in press). Mycotox- Morton, J. 1987. Fig, p. 47–50. In: Fruits of warm Serrano, L., J. Ramon, J. Segarra, V. Medina, M.A. ins in dried figs. Proc. Third Int. Fig Symp. climates. Julia F. Morton, Miami, FL. Achon, M. Lopez, and M. Juarez. 2004. New Kjellberg, F., P.H. Gouyon, M. Ibrahim, M. Norberto, P.M., N.N.J. Chalfun, M. Pasqual, R.D. approach in the identification of the causal Raymond, and G. Valdeyron. 1987. The sta- Veiga, and J.H. Mota. 2001. Efeito de epoca agent of fig mosaic disease. Acta Hort. bility of the between dioecious figs de poda, cianamida hidrogenada e irrigacao 657:559–566. and their : A study of Ficus carica na producao antecipada de figos verdes. Storey, W.B. 1975. Figs, p. 568–588. In: J. Janick L. and L. Evolution Int. J. Pesquisa Agropecuaria Brasileira. 36:1363– and J.N. Moore (eds.), Advances in fruit Org. Evolution 41:693–704. 1369. breeding. Purdue University Press, West Krezdorn, A.H. and S.K. Glasgow. 1970. Propaga- Obenauf, G., M. Gerdts, G. Leavitt, and J. Crane. Lafayette, IN. tion of Ficus carica on tropical species of Ficus. 1978. Commercial dried fig production in Tous, J. and L. Ferguson. 1996. Mediterranean Proc. Tropical Region Amer. Soc. Hort. Sci. California. Univ. of Calif. Agr. Ext. Leaflet fruits, p. 416–430. In: J. Janick (ed.), Progress 14:156–164. 21051, Oakland, CA. in new crops. ASHS Press, Arlington, VA. McBeth, C.W. 1949. Nematodes affecting figs, Saleeb, W.F. and W. Storey. 1975. The genetics of Zohary, D. and P. Spiegel–Roy. 1975. Beginnings p. 16–17. In: 3rd Ann. Res. Conf. Calif. Fig persistent vs. caducous synconia in fig. Hort- of fruit growing in the old world. Science Inst. Proceed. Science 10:328. 187:319–327.

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