diversity Review Cultivar-Groups in Cucurbita maxima Duchesne: Diversity and Possible Domestication Pathways Fernando Sebastián López-Anido Cátedra de Genética, Facultad Ciencias Agrarias, Universidad Nacional de Rosario-IICAR Conicet, Zavalla S2125ZAA, Argentina; [email protected] Abstract: Domesticated Cucurbita has been remarked as one of the plant genera with the highest diversity in color, shape and fruit dimensions. Their economic and cultural values are related to the consumption of the mature or immature fruits, seeds, flowers, and to the use as decoration. The wild ancestor of C. maxima, the ssp. andreana has an actual scattered and disjointed distribution, associated with megafauna seed disperser syndrome. It was domesticated in South America around 9000–7000 years BP. The cultivar-group is a subspecific category for assembling cultivars on the basis of defined similarity. The work describes and pictures nine cultivar-groups for the species, Banana, Turban, Hubbard, Show, Buttercup, Zapallito, Plomo, Zipinka and Nugget. The molecular and a morphological join data analysis scatter biplot showed Turban and Buttercup in a central position, suggesting a first step in the domestication pathway associated with seed and immature fruit consumption; afterward, bigger bearing fruits groups were selected for their mature fruit flesh quality on one hand, and bush type, short day induction and temperate climate adaptation on the other hand. The striking domesticated Brazilian accession MAX24 intermediate between cultigens and ssp. andreana strengthens, in concordance with archeological remains, the possible domestication place of the species more easternward than previously believed. Citation: López-Anido, F.S. Keywords: pumpkin; domestication; cultivar-groups Cultivar-Groups in Cucurbita maxima Duchesne: Diversity and Possible Domestication Pathways. Diversity 2021, 13, 354. https://doi.org/ 10.3390/d13080354 1. Cucurbita 1.1. Extant Wild Species Academic Editor: Mario A. Pagnotta Cucurbita (2n = 20) is a well-defined New World genus within the tribe Cucurbitae [1]. Wild species are herbaceous, multi-branched, procumbent or climbing vines. The stems are Received: 10 July 2021 slender, and the leaves are arranged on them alternately [1]. Plants are monoecious and Accepted: 30 July 2021 predominantly staminate, with large yellow-orange (rarely pale yellow) flowers pollinated Published: 31 July 2021 in early morning by solitary bees of the genera Poponapis and Xenoglossa [2]. Fruits are small (5–10 cm long), round, indehiscent, with a lignified rind, thin fibrous, light-colored or pale Publisher’s Note: MDPI stays neutral usually bitter flesh and numerous, relatively small seeds [3]. Around twelve wild species with regard to jurisdictional claims in are generally recognized; six belong to the perennial, xerophytic group, Cucurbita cordata published maps and institutional affil- Watson, C. digitata Gray, C. foetidissima Kunth, C. palmata Watson, C. pedatifolia Bailey and C. iations. radicans Naudin. This group has a distribution range from southern-western United States and Baja California to northern-central and southern Mexico [4]. The annual, mesophytic group comprises Cucurbita argyrosperma Huber ssp. sororia Merrick & Bates, C. lundelliana Bailey, C. okeechobeensis Bailey ssp. martinezii Andres and Nabhan and ssp. okeechobeensis, C. Copyright: © 2021 by the author. pepo L. ssp. fraterna Lira et al., ssp. ovifera Decker var. ozarkana Decker and var. texana Filov, Licensee MDPI, Basel, Switzerland. C. ecuadorensis Cutler and Whitaker and C. maxima Duchesne ssp. andreana Filov. For this This article is an open access article group, the distribution is more scattered and disjointed, ranging from central United States, distributed under the terms and Florida, Texas, the pacific and gulf coast of Mexico, southern Mexico, northern Central conditions of the Creative Commons America, Ecuador, Peru, Bolivia, northwestern and central Argentina and Uruguay [4,5]. As Attribution (CC BY) license (https:// it is evident, the actual Mexico territory is the center of diversity of wild Cucurbita species. creativecommons.org/licenses/by/ 4.0/). Diversity 2021, 13, 354. https://doi.org/10.3390/d13080354 https://www.mdpi.com/journal/diversity Diversity 2021, 13, 354 2 of 19 Diversity 2021, 13, 354 northwestern and central Argentina and Uruguay [4,5]. As it is evident, the actual Mexico2 of 19 territory is the center of diversity of wild Cucurbita species. 1.2.1.2. SeedSeed DispersalDispersal InIn thethe majority of of the the botanical botanical and and ecological ecological descriptions descriptions of the of thewild wild CucurbitaCucurbita spe‐ species,cies, the the seed seed dispersal dispersal system system is is overlooked. overlooked. One One of of the the reasons reasons is is that until thethe NewsonNewson andand MihlbachlerMihlbachler [[6]6] findingfinding ofof abundantabundant wildwild CucurbitaCucurbita seedsseeds inin mastodonmastodon dungdung atat the the Page-LadsonPage‐Ladson archeological archeological site, site, no no clear clear evidence evidence for afor zoochory a zoochory mechanism mechanism was recorded. was rec‐ Thisorded. confirmed This confirmed the previous the previous hypothesis hypothesis of Barlow of [ 7Barlow] that C. [7] foetidissima that C. foetidissimawas a clear was example a clear ofexample the megafauna of the megafauna (>1000 kg) (>1000 anachronisms kg) anachronisms syndrome, syndrome, proposed by proposed Jansen and by Jansen Martin and [8]. TheMartin mass [8]. megafauna The mass extinction megafauna around extinction 12,000 yearsaround ago 12,000 left wild yearsCucurbita ago leftspecies wild strandedCucurbita asspecies anachronisms stranded inas aanachronisms post-megafauna in a world,post‐megafauna producing world, fruit that producing few or fruit no animals that few eat, or withno animals seeds that eat, go with undispersed seeds that and go undispersed orphans of mutualistic and orphans partners of mutualistic that shaped partners a mosaic- that likeshaped landscapes, a mosaic offering‐like landscapes, an abundance offering of disturbed an abundance habitat of in disturbed a niche-diverse habitat ecosystemin a niche‐ suitablediverse ecosystem for climbing suitable vines for plants climbing as Cucurbita vines plants[9,10]. as This Cucurbita is crucial [9,10]. to This understand is crucial the to actualunderstand distribution the actual of these distribution species of that these relied, species since that the relied, beginning since ofthe the beginning Holocene, of onthe alternativeHolocene, seedon alternative dispersals seed as buoyancy dispersals of as fruits buoyancy along streams,of fruits along gravity, streams, seed predators gravity, seed and eventuallypredators and anthropogenic eventually activity.anthropogenic This accounted activity. forThis a shrinkingaccounted and for a fragmentation shrinking and in frag the‐ range,mentation and evenin the that range, some and species even could that some have species gone extinct. could Ashave an gone example, extinct.C. okeechobeensis As an exam‐ hasple, an C. allopatricokeechobeensis distribution has an allopatric in Mexico distribution and Florida, in andMexico in the and latter Florida, site, and the populationin the latter wassite, restrictedthe population to the was endoreic restricted basin to of the the endoreic Lake Okeechobee. basin of the Moreover,Lake Okeechobee.C. maxima Moreossp.‐ andreanaver, C. maximashows patchyssp. andreana distribution shows in patchy small specificdistribution populations in small in specific Peru and populations Bolivia [11 in], andPeru in and Argentina Bolivia [11], is associated and in Argentina with disturbed is associated roadsides, with agriculturedisturbed roadsides, field fences, agriculture fallows andfield field fences, drainages fallows [ 12and] (Figure field drainages1). [12] (Figure 1). FigureFigure 1.1. FruitsFruits ofof C.C. maximamaxima ssp.ssp. andreanaandreana inin anan agricultureagriculture fieldfield wirewire fencefence atat Zavalla, Zavalla, Santa Santa Fe Fe province,province, Argentina. Argentina. LackLack ofof fruitsfruits and and seeds’ seeds’ dispersal dispersal is is apparent; apparent; dry dry light light brown brown ones ones are are from from the previous growing season, yellow‐green ones from the current year. the previous growing season, yellow-green ones from the current year. 1.3.1.3. AnthropogenicAnthropogenic SeedSeed DispersalDispersal ItIt hashas been pointed pointed out out that that bottle bottle gourd gourd (Lagenaria (Lagenaria siceraria siceraria, Cucurbitaceae), Cucurbitaceae) was was car‐ carriedried as asa utilitarian a utilitarian already already domesticated domesticated (mutualism) (mutualism) species species through through Beringia Beringia into into the thenew new world world and andwas wasthereafter thereafter involved involved and reliant and reliant on humans on humans [13]. In [13 this]. Insense, this we sense, can wehypothesize can hypothesize that Paleoindians that Paleoindians as gatherers as gatherers recognized recognized the smaller the smaller gourds gourds of wild of Cucur wild‐ Cucurbitabita with witha potential a potential use and use started and started a virtuous a virtuous circle circle in which in which the gourds, the gourds, that thatwere were mal‐ maladaptiveadaptive of seed of seed dispersers, dispersers, as asthey they became became extinct, extinct, found found in in humans humans a a proxy, alreadyalready familiarizedfamiliarized withwith gourds,gourds,