Emergence Of The Sweet Dessert Watermelon, Citrullus Lanatus

Emergence of the Sweet Dessert Watermelon, Citrullus lanatus, in Mediterranean Lands During the Roman Era

Harry S. Paris*

Agricultural Research Organization, Newe Ya‘ar Research Center, P. O. Box 1021, Ramat Yishay 3009500, Israel e-mail: [anonimizat]

Abstract

Watermelons, Citrullus species, are native to Africa. Archaeological remains, iconography, ancient literature, and the presence of wild and primitive watermelons in northeastern Africa indicate that the dessert watermelon, C. lanatus, is native to that region. The dessert watermelon was nurtured and domesticated there, for water and food, over 4000 years ago. Although the domesticated watermelons of Egypt and Sudan were probably not bitter, there is no evidence to indicate that they were sweet. Indeed, the extant primitive watermelons known as gurma in Egypt and gurum in Sudan are spherical and small ( 14 cm diameter), with watery but bland, white or pale green fruit flesh. Hebrew-language literature from the first centuries CE indicates that, by the time of the Roman Empire, sweet dessert watermelons were esteemed in the Land of Israel, and thus likely were present in other Mediterranean lands as well. The ripe fruit flesh of the dessert watermelons of that time, which was probably distinctly colored rather than pale, was eaten raw and had a sweetness which was comparable to that of figs, grapes, and pomegranates. The seeds were not consumed.

Keywords: Citrullus lanatus, evolution under domestication, watermelon

Introduction

The dessert watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai, is one of the most cooling, refreshing, and appreciated food items on hot summer days. Watermelons are among the most widely grown vegetable crops in the warmer regions of the world, with over 3,400,000 hectares planted and over 100,000,000 t harvested annually (Wehner 2008). However, the sweet dessert watermelons that are so familiar today are derived from ancestors that, anthropocentrically, were much inferior.

The xerophytic genus Citrullus (2n = 2x = 22) is native to Africa. In accordance with the classification of Chomicki and Renner (2015), there are seven species in the genus. Three of them, C. ecirrhosus Cogn., C. rehmii De Winter, and C. naudinianus (Sond.) Hooker f., grow wild in southern Africa and have not been introduced to cultivation. The other four Citrullus species are cultivated to a lesser or greater extent. The colocynth, C. colocynthis (L.) Schrad., is native to northern Africa. The citron watermelon, C. amarus Schrad., is native to southern Africa. The egusi watermelon, C. mucosospermus (Fursa) Fursa, is native to western Africa. Recently, I presented a view, based on archaeological remains, iconography, ancient literature, and the modern presence of wild and primitive watermelons in Sudan and Egypt, that the familiar, esteemed dessert watermelon, C. lanatus, is native to northeastern Africa (Paris 2015).

However, in spite of the familiarity, dating to 5000 years ago, of ancient Egyptian civilizations with watermelons, I could find no evidence showing that the dessert watermelons of Egyptian antiquity were sweet. Here I will discuss the evidence for the emergence of sweet dessert watermelons during the Roman era.

Materials & Methods

Sources of evidence

A multidisciplinary approach that encompasses botany, horticulture, cookery, philology and archaeology is necessary to best assess crop plant history (Dalby 2003). For cucurbit crops, archaeological remains, iconography, and literature have provided much information concerning their development under cultivation (Paris 2000; Janick et al. 2007).

Some diagnostic features of Citrullus

Citrullus is readily distinguished from other cucurbit genera by the pinnatifid shape of its leaf laminae (Paris et al. 2013). The flowers are solitary and have five light yellow petals. Most of the flowers are are staminate, a pistillate or hermaphroditic flower appearing at every seventh or eighth leaf axil (Rosa 1928). Ovaries and primordial fruits are lanate, becoming glabrous, smooth and glossy as they grow. Usually 30–40 days ensue from anthesis to fruit maturity. External indications of fruit ripening are subtle (Thompson and Kelly 1957). If stored in a cool, shady place, watermelons can keep for weeks or even months after harvest without serous deterioration of their quality (Keith-Roach 1924; Rushing et al. 2001).

Watermelon fruits can weigh as much as 100 kg but most modern, commercially available watermelons range from 3–13 kg. Fruit shape can be spherical, globular, oval, or oblong. The watermelon rind consists of two layers. The surface of the thin, glossy exocarp is typically boldly striped in two shades of green; the stripes are jaggedly edged and range in breadth from very narrow to very broad. The thick, white mesocarp is wet and hard. Underneath the rind is the watery fruit flesh or endocarp, which is the portion of the fruit that is usually eaten. Early in development, the fruit flesh is hard, white or otherwise pale-colored, and insipid. In citron watermelons, the fruit flesh remains hard, nearly colorless and tasteless to fruit maturity (Xu et al. 2012). In sweet dessert watermelons, the flesh of the maturing fruit becomes soft and accumulates carotenoid pigments and sucrose (Elmstrom and Davis 1981; Brown and Summers 1985; Soteriou et al. 2014). Color begins to accumulate between 2 and 3 weeks after anthesis, first around the developing seeds and thereafter gradually spreading throughout the endocarp (Perkins-Veazie et al. 2012). Depending on the genotype, the flesh color of ripe watermelon fruits can range from red, pink, orange, yellow, or a mixture of these colours, to green or white (Gusmini and Wehner 2006). The range in texture of the ripe fruit flesh can be described as crisp, tender, or liquefied, and coarsely or finely grained. Each fruit can contain several hundred seeds that, to the casual observer, are scattered throughout the flesh and, to the consumer, are of much annoyance. The seeds of dessert watermelons are hard, flat and oval and, depending on the genotype, range in length from 10 to 16 mm and are black, brown, tan, white, yellow, or red, and can be patterned with a second color.

Dessert watermelons, Citrullus lanatus, are sometimes confused with melons, Cucumis melo L., as both are often large and sweet. The most salient features distinguishing the two are the shape of the leaf laminae, distribution of staminate and pistillate flowers on the plant, range of fruit shape, fruit surface features, wetness of the fruit, thickness of the fruit rind, fruit flesh color, and shape color, and distribution of seeds within the fruit (Paris et al. 2012). In the field, watermelons ripen evenly over the course of the harvest season but melons ripen in distinct waves (Rosa 1924; McGlasson and Pratt 1963; Pratt et al. 1977). Watermelons have no well-marked indicators of fruit ripening whereas melons typically become aromatic and yellow, and abscise from the plant upon ripening (Isenberg et al. 1987; Nonnecke 1989). Watermelons have a much longer shelf-life than most melons but are subject to breakage if not handled properly (Whitaker and Davis 1962; Robinson and Decker-Walters 1997). In watermelons, the seeds are distributed within the fruit flesh but in melons the fruit flesh is free of seeds.

Possible pitfalls in interpretation of literature

Although iconography has been the most important source of evidence in understanding cucurbit crop history (Eisendrath 1961), fruit sweetness is not a trait that is readily amenable to illustration or detection in archaeological remains. Literature is a potentially rich source of information concerning possible sweetness of cucurbit fruits (Paris et al. 2012). Generally, though, food items were considered by ancient writers to be familiar to everyone, and thus in no need of description, and were usually discussed only in reference to their supposed dietary or medicinal effects (Dalby 2003). Off-hand, indirect descriptions of foods can sometimes be gathered in other contexts, especially medicine, religion, travel, and cookery. No direct description of the characteristically smooth, glossy, green-striped rind, or the taste, texture, or color of the fruit flesh or seeds of watermelons has been found in literature of antiquity (Janick et al. 2007; Paris 2015).

Caution must be exercised in interpretation of the ancient literature. Adjectives tend to be used differently across languages, contexts, geographic areas, and periods of time (Paris et al. 2012). For example, “sweet” can be synonymous with sugary or not bitter, not sour, not salty, or not spicy. Also, what might have been considered sweet in ancient times might not be considered sweet today, given recent development of cultigens with greater sweetness. The adjective “red” has been variously used for orange, purple, and brown, and “yellow” has been used for orange. Nouns have also been used indiscriminantly. The word “melon” has been used in American English for both Citrullus and Cucumis melo. Similar examples occur for the medieval Latin pepo and melones, and Arabic battikh. The intention of such words has to be interpreted in the context of time period, language, and geographic area.

Watermelons in Literature of Antiquity

Biblical Hebrew

The Children of Israel, during their sojourn in the Sinai Desert after the exodus, longed for five vegetables they knew from the Land of Egypt; these were, respectively, the qishu’im (vegetable melons), avattihim (watermelons), hazir (leeks), bezalim (onions) and shumim (garlics) (Numbers 11:5). As watermelons were mentioned together with other vegetables, they were considered to be just like the others, to be eaten raw, cooked, or pickled. They were not like modern sweet dessert watermelons, otherwise they would have been craved to be eaten first and immediately in a desert environment.

Centuries later, in the Land of Israel, the word used for a field of cucurbits was miqsha (Isaiah 1:8). The word miqsha is derived from the word qishu’im. Indeed, in those times, watermelons must have been of secondary importance to the vegetable melons, and there is no evidence suggesting that the watermelons were sweet.

Greek (400 BCE – 355 CE)

The word pepon of classical Greek, literally a sun-ripened fruit, usually referred specifically to watermelon (Liddell and Scott 1948; Andrews 1958; Stol 1987; Grant 2000). The Greek doctor Hippocrates, in approximately 400 BCE, wrote that the pepones were easily digestible (Jones 1967). Likewise, Dioscorides, in 70 CE, wrote that the flesh of the pepon is easily digestible and diuretic, and prescribed the rind of the pepon, to be applied on top of the head, for children suffering from heat stroke (Osbaldeston and Wood 2000; Beck 2005). A century later, Galen wrote that the pepon was cold and wet, and a diuretic, and the melopepon less so (Grant 2000; Powell and Wilkins 2003). Clearly, to all of these doctors, the pepo they were describing was the watermelon, Citrullus lanatus. The melopepon, introduced later and of lesser effect, would appear to be the melon, Cucumis melo.

Athenaeus, in The Learned Banqueters (late second century), quoted thousands of lines of verse written by approximately 1000 Greek authors from various times and localities (Olson 2006). One of them, Phaenias, is quoted as stating that the pepon is edible, except for the seeds, when the flesh becomes soft. Another, Diocles, wrote that the best kolokyntas were round, very large, glukeian (sweet), and easy to digest. The word kolokyntas was usually applied to bottle gourds, Lagenaria siceraria (Mol.) Standl., but for some ancient Greek speakers the word was applied to watermelons.

Latin (77 – 516 CE)

Pliny, in his Historia Naturalis (77 CE), described the pepo as a most refreshing and cooling food (Rackham 1950; Jones 1951). This description would fit the watermelon, Citrullus lanatus. The melopepo (apple-pepo) was a new introduction resembling a quince that, upon ripening, turned yellow, became aromatic, and, significantly, spontaneously detached from the plant. Obviously, the melopepo was a cultigen of melon, Cucumis melo. Quintus Gargilius Martialis, around 260 CE, wrote that the pepone were good to eat after removal of the rind and pits (Maire 2007). De Observantia Ciborum (510 CE) has a list 101 foods, including three cucurbits (Mazzini 1984). The pepone are not listed with the other two cucurbits. Instead, they are among pomegranates, grapes, and figs, which are sweet, juicy fruits that are usually eaten raw when ripe. Anthimus, in De Observantia Ciborum Epistula (516 CE), indicates that the melones were to be eaten well-ripened, fresh with the seeds still mixed in the flesh (Grant 2007).

Hebrew (150 – 400 CE)

Three large codices of Jewish Law were compiled in Israel during the first centuries CE. They are easily searched at Mekhon Mamre (http://www.mechon-mamre.org). The first of these is the Mishna, which was compiled during the latter half of the second century. The second, the Tosefta, was compiled approximately a century later and differs in some of its material from the Mishna. The third, the Jerusalem Talmud, probably compiled during the latter half of the fourth century, includes a text very similar to that of the Mishna but with much exposition. All three codices are arranged in sedarim (orders) each of which has varying numbers of massakhtot (tractates). The Mishna has 63 tractates sorted into six orders.

Some of the tractates refer to edible-fruited cucurbits, most notably the ones on Kil’ayim (Intermingling), Ma‘asrot (Tithing), Terumot (Contributions), and ‘Oqazin (Peduncles). Four edible cucurbits are often mentioned, these four in Hebrew being the qishu’im (vegetable melons, Cucumis melo), delu‘im (bottle gourds, Lagenaria siceraria), avattihim, and melafefonot. A fifth edible cucurbit, the qarmulin, is mentioned only in the latter two works, apparently being a new introduction with an appearance and use similar to the delu‘im. The qarmulin have been identified as sponge gourds, Luffa aegyptiaca Mill. (Janick et al. 2007; Avital and Paris 2014).

The four edible-fruited cucurbits are considered together in the tractate Kil’ayim because of the concern given to their vines intermingling with one another. There are some elements of practicality in this prohibition. On the other hand, in the Jerusalem Talmud version (Kil’ayim 1:2, 2a), there is also a recantation of Mediterranean agricultural folklore: “A person takes a seed from the flesh of an avattiah and a seed from the flesh of an apple and puts them together in the same hole and they unite to become an intermingling. This is called in the Greek language molefefon.” Thus the myth of the apple-pepo was carried across three languages, Greek, Latin, and Hebrew. More importantly, it allows definite identification of the Hebrew melofefonot as melons, Cucumis melo. Another passage from the Jerusalem Talmud (Kil’ayim 1:8, 4a) has this comment: “Prohibited is the insertion of cuttings from grapevines into an avattiah lest it throw its waters into them.” The avattiah, like the Greek pepon and Latin pepo, was a large, watery fruit, the watermelon, Citrullus lanatus.

The four edible-fruited cucurbits are considered together in the first chapter of the tractate on tithing, Ma‘asrot. The qishu’im and delu‘im were to undergo piqqus, rubbing off of their hairs, prior to eating. Hence, these two cucurbit fruits, vegetable melons and bottle gourds, were eaten young and immature, when they were hairy. In contrast, the avattihim were to be tithed after they underwent shilluq, smoothing or polishing for removal of the dust that accumulated on them. Therefore the avattihim, watermelons, were eaten when ripe. Corroborating evidence for the eating of the watermelons when they were ripe is also found in the Mishna tractate on peduncles (‘Oqazin 2:3), in which it is mentioned that a partially withered pomegranate or watermelon is not eaten. The tractate on tithing in the Tosefta indicated that the melafefonot, melons, were to be tithed after they were taken out of the field and gathered (Ma‘asrot 1:6). Specifically, the grower was obliged to tithe each wave (harvest) of ripened melons.

Melon seeds were to be tithed but watermelon seeds were not, because the latter could not be used as food (Jerusalem Talmud, Ma‘asrot 1:2, 2b). This might at first seem strange as, today, watermelon seeds are consumed in many areas. However, watermelon seeds of the time were quite small, only 11 mm long (Cox and van der Veen 2008; Kislev and Simhoni 2009), and given their thick, hard seed coats were not particularly suitable for use as food.

The tractate on contributions, Terumot, contains a discussion on the amount of time, post-harvest, that various fruits and vegetables are acceptable as contributions. As would be expected from highly perishable, young cucurbit fruits, the vegetable melons and bottle gourds were suitable for contribution for only one day after harvest (Tosefta, Terumot 4:5). The melons were acceptable for three days. The watermelons are not mentioned in this context, apparently because they had a long shelf life. Also unlike the other three cucurbits, watermelons could not be gathered for sale in a pile. Instead they had to be laid out one-by-one (Jerusalem Talmud, Ma‘asrot 1:4, 4a), indicating that they were fragile, and thus very different from the modern cultivars of watermelons that have been bred for adaptation to long-distance shipping.

Finally and most significantly, watermelons differed in one more way from the other edible cucurbits. In the tractate on tithing, watermelons are discussed together with figs, table grapes, and pomegranates. Fruits that were picked in the garden or field and eaten there were exempt from tithing (Mishna, Ma‘asrot 2:6; Jerusalem Talmud, Ma‘asrot 2:4, 11a). Figs were simply chosen and eaten, grapes were picked one-by-one from a cluster and eaten, pomegranates were plucked and eaten, and watermelons were sliced and eaten. Evidently, the watermelons of the latter half of the second century in Israel, like figs, table grapes, and pomegranates, were common fruits that were eaten raw without any culinary preparation and, like them, were juicy and sweet.

Discussion

Domesticated plants are derived from small samples of wild source populations, and thus are themselves founder populations that contain only a small fraction of the genetic diversity of their wild ancestors (Ladizinsky 1985). Cultigens have various traits that were selected early and continually in the domestication process, such as lack of bitterness, increased size of the

harvested parts, increased yield and novel coloration (Heslop-Harrison and Schwarzacher 2012). The sweet dessert watermelon, Citrullus lanatus, which has relatively little genetic diversity (Levi et al. 2001; Reddy et al. 2015), follows this general pattern of crop-plant domestication. The fruit flesh of wild and primitive Citrullus is bitter or insipid, hard and pale-coloured (Wehner 2008). Non-bitterness of the fruits was probably the first and most important trait to be selected in the process of watermelon domestication. As non-bitterness is conferred by a single recessive gene (Wehner 2007), this trait should have been relatively easy to maintain if isolation from neighbouring wild populations was feasible. The modes of inheritance of hard versus soft and of insipid versus sweet flesh in Citrullus have not been illuminated.

Although it is agreed that the genus Citrullus is of African origin, there has been major disagreement concerning where in Africa the dessert watermelon originated. Much of the controversy stems from phenotypic variations that overlap among C. colocynthis, C. amarus, C. mucosospermus, and C. lanatus, and the weak crossability barriers among these four species. Regardless of species, wild and primitive Citrullus fruits typically have hard, bitter or bland, weakly coloured flesh and, as indicated by Wehner (2008), this situation has repeatedly been a source of incorrect taxonomic identifications. Archaeological remains, iconography, and literature, as well as the modern presence of wild and primitive watermelons in Sudan and Egypt, support the idea that the dessert watermelon, C. lanatus, is native to northeastern Africa (Paris 2015).

The present investigation, which has focused mainly on ancient literature, has attempted to define a narrower time frame and geographical range within which the dessert watermelons

having non-bitter, tender, highly coloured, sweet flesh were developed. The latest possible date for this time frame is provided by illustrations of both red-flesh sweet dessert watermelons and

white-flesh citron watermelons in illustrated manuscripts prepared in northern Italy dating to the end of the 14th century (Paris et al. 2009, 2013).

Ancient Greek, Latin, and Hebrew writers clearly distinguished between watermelons and melons. The watermelon, as pepon, pepo, and avattiah, was a large, watery, cooling but fragile fruit, eaten raw when ripe, except for the rind and pits. The melon, as melopepon, melopepo, and melafefon, was the mythological intermingling of apple with watermelon, less watery and less cooling than watermelon, lobed, turning yellow, aromatic, and detaching from the plant when ripe, with a short, 3-day shelf life.

The earliest evidence for the existence of sweet dessert watermelons is primarily from the Hebrew literature. The context is not an appraisal or a praising of their sweetness but, instead, an exemption to the Jewish instruction of tithing. Under particular conditions, several succulent, sweet fruits, figs, table grapes, and pomegranates, are exempt from tithing and, together with them, so are watermelons. Only watermelons and not melons or other cucurbits are treated in this context. Sweet melons emerged later, in Khorasan, Central Asia, during early medieval times, reaching Mediterranean lands in the eleventh century (Paris et al. 2012).

The Hebrew evidence for the existence of sweet dessert watermelons in Mediterranean lands by Roman times is corroborated by a contemporary Greek writing and a Latin writing from just after the fall of the Roman Empire. In the late second century, Athenaeus quoted Diocles as stating that the best kolokyntas are glukeian, sweet (Olson 2006). The early sixth-century Latin De Observantia Ciborum lists the pepone among pomegranates, grapes and figs, confirming the presence of sweet watermelons in what is now Italy (Mazzini, 1984). Thus, sweet watermelons had diffused to Europe centuries before their earliest recorded presence in Moorish Spain, in the Cordoban Calendar of 961 CE (Pellat, 1961).

Conclusion

Sweet dessert watermelons were selected from non-sweet ancestors. By the time of the Roman Empire, sweet dessert watermelons were a familiar and esteemed produce item in Israel, and probably in other Mediterranean lands as well.

Acknowledgements

Financial support of the Lillian Goldman Charitable Trust (New York) is gratefully acknowledged.

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