Overview of the origins and history of the five major cucurbit crops: issues for ancient DNA analysis of archaeological specimens

The gourd family, Cucurbitaceae, contains five vegetable crops of worldwide importance, the pumpkins and squash (Cucurbita spp.), watermelons (Citrullus lanatus), melons (Cucumis melo) and cucumbers (Cucumis sativus). Here is presented a synopsis of the origin and history of these cucurbit crops. Historical records of the use of cucurbits by people take the form of archaeobotanical finds, iconography and literature. The weight of the evidence indicates that Cucurbita spp. were first cultivated in the Americas at least 10,000 years ago, and that by 1492 ce a number of cultivar-groups of pumpkins and squash had been developed by indigenous American peoples. Watermelons were cultivated in northeastern Africa at least 4,000 years ago, first probably as a source of fresh water. Melons and cucumbers are native to Asia, probably initially cultivated for the use of the young fruits as vegetables. Melons spread to eastern Africa at an early date, but cucumbers are probably a more recent domesticate and spread westwards later, reaching Europe in early medieval times. Sequencing of cucurbit plant genomes and advances in ancient DNA research offer much promise for obtaining an improved assessment of cucurbit crop origins, specifically the genetic constitution and geographical home of ancestral source populations. Next-generation genomic sequencing, if applied to an appropriate array of archaeological cucurbit remains and modern germplasm, could contribute much to the understanding of the history and evolution under domestication of cucurbit crops.     

Historical overview on domesticated plants in China with special emphasis on the Cucurbitaceae

Cultivation of plants in northern China began at an early date. A number of domesticates were derived from native species, and others were introduced from southeastern Asia. Many vegetable species are included in myths and stories of ancient China. These traditional stories, as well as ancient agricultural and medicinal books, often mention cultivated members of the Cucurbitaceae. Twelve genera and 18 species of cucurbits are currently under cultivation in China. A number of them appear to be endemic to Indochina, while others were introduced from Western Asia and the New World. A recent trip to China and a survey of Chinese literature indicated that many cucurbits are consumed in the immature state as vegetables, some are eaten as fruits, and various species are used for medicine and a variety of other purposes. Resumen histórico de las plantas domésticas de la China con énfasis en las Cucurbitaceae. El cultivo de las plantas comenzó en una edad temprana en el norte de China. Varias plantas domésticas fueron derivadas de especies nativas, mientras que otras fueran introducidas desde el sudeste de Asia. Las historias y los mitos de la China antiqua cuentan de diversas especies vegetales. Estos relatos tradicionales, tanto como los viejos libros de las agricultura y medicina, frecuentemente mencionan los miembros cultivados de las Cucurbitaceae. Hoy en día se cultivan doce géneros y dieciocho especies de las familia en la China. Algunas Cucurbitaceae parecen ser endémicos de la Indochina, mientras que otras fueron introducidas desde el oeste de Asia y del Nuevo Mundo. Un viaje reciente a la China y un estudio de la literatura China indicaron que muchas Cucurbitaceae son consumidas en el estado inmaduro, algunas son comidas como frutas, y varias especies son utilizadas en medicina otros propósitos.     

Gaps and perspectives of pathotype and race determination in <Emphasis Type="Italic">Golovinomyces cichoracearum</Emphasis> and <Emphasis Type="Italic">Podosphaera xanthii</Emphasis>

Golovinomyces cichoracearum and Podosphaera xanthii (family Erysiphaceae) are the most important species causing cucurbit powdery mildew (CPM), a serious disease of field and greenhouse cucurbits. Both species are highly variable in their pathogenicity and virulence, as indicated by the existence of large number of different pathotypes and races. Various independent systems of CPM pathotype and race determinations and denominations are used worldwide. CPM pathotype identification is based on intergeneric and interspecific differences in host-CPM interactions. The most commonly used set of CPM pathotype differentials includes one genotype from four species representing three agriculturally important cucurbit genera plus two genotypes from a fifth species, melon Cucumis melo L. CPM races are characterized by specialization on different cultivars or lines of one host species and have, to date, been differentiated only on melon (C. melo L.). The most frequently used set of melon differentials includes 11 genotypes that can differentiate CPM races originating from melon and other cucurbits, e.g., cucumber, Cucurbita spp., and watermelon. In this paper, we critically review the current state, gaps, and perspectives in our understanding of pathogenicity variation in these two CPM pathogens at the pathotype and race levels.     

24β-Ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)-dehydrolophenol in seeds of three cucurbitaceae species

The structures of two 4α-methylsterols is isolated from Cucumis sativus(Cucurbitaceae) seeds were determined based mainly on their ¹³CNMR spectra as 24β-ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)- dehydrolophenol, respectively, of which the former is a new sterol from natural sources. These two 4α-methylsterols were identified in the seeds of two other Cucurbitaceae species, Lagenaria leucantha var. Gourda and Citrullus battich. The probable biogenetic significance of the two 4α-methylsterols is discussed. Other 4α-methylsterols identified in the seeds of the three Cucurbitaceae species were obtusifoliol, cycloeucalenol and gramisterol.     

Taxonomic significance of trichomes micromorphology in cucurbits

Studies on trichomes micromorphology using Scanning Electron Microscope (SEM) were undertaken in 23 species with one variety under 13 genera of the family Cucurbitaceae (viz., Benincasa hispida (Thunb.) Cogn., Citrullus lanatus (Thunb.) Matsum. & Nakai, Cucumis melo var. agrestis Naudin, Cucumis sativus L., Diplocyclos palmatus (L.) C. Jeffrey, Edgaria dargeelingensis C.B. Clarke, Gynostemma burmanicum King ex Chakr., Gynostemma pentaphyllum (Thunb.) Makino, Gynostemma pubescens (Gagnep.) C.Y. Wu, Hemsleya dipterygia Kuang & A.M. Lu, Lagenaria siceraria (Molina) Standl., Luffa acutangula (L.) Roxb., Luffa cylindrica M. Roem., Luffa echinata Roxb., Melothria heterophylla (Lour.) Cogn., Melothria leucocarpa (Blume) Cogn., Melothria maderspatana (L.) Cogn., Sechium edule (Jacq.) Sw., Thladiantha cordifolia (Blume) Cogn., Trichosanthes cucumerina L., T. cucumerina var. anguina (L.) Haines, Trichosanthes dioica Roxb., Trichosanthes lepiniana (Naudin) Cogn. and T. tricuspidata Lour.). The trichomes in the family Cucurbitaceae vary from unicellular to multicellular, conical to elongated, smooth to ridges, with or without flattened disk at base and cyctolithic appendages, thin to thick walled, curved at apices to blunt. Trichomes micromorphology in the family Cucurbitaceae was found significant taxonomically.     

Uromyces umiamensis, a new rust species on Momordica cochinchinensis in India

Uromyces umiamensis is described as a new rust fungus (Basidiomycota, Uredinales) of Momordica cochinchinensis (Cucurbitaceae) from Meghalaya, in northeastern India. The species differs from the known Uromyces species on members of Cucurbitaceae in terms of the character of the teliospores and aeciospores and its apparently demicyclic life cycle. Besides U. yakushimensis and the present species, all Uromyces species known from cucurbits occur in the New World. A key to known Uromyces species on Cucurbitaceae is provided.     

A tobacco ringspot virus-based vector system for gene and microRNA function studies in cucurbits

Cucurbits are economically important crops worldwide. The genomic data of many cucurbits are now available. However, functional analyses of cucurbit genes and noncoding RNAs have been impeded because genetic transformation is difficult for many cucurbitaceous plants. Here, we developed a set of tobacco ringspot virus (TRSV)-based vectors for gene and microRNA (miRNA) function studies in cucurbits. A TRSV-based expression vector could simultaneously express GREEN FLUORESCENT PROTEIN (GFP) and heterologous viral suppressors of RNA silencing in TRSV-infected plants, while a TRSV-based gene silencing vector could knock down endogenous genes exemplified by PHYTOENE DESATURASE (PDS) in Cucumis melo, Citrullus lanatus, Cucumis sativus, and Nicotiana benthamiana plants. We also developed a TRSV-based miRNA silencing vector to dissect the functions of endogenous miRNAs. Four representative miRNAs, namely, miR159, miR166, miR172, and miR319, from different cucurbits were inserted into the TRSV vector using a short tandem target mimic strategy and induced characteristic phenotypes in TRSV-miRNA-infected plants. This TRSV-based vector system will facilitate functional genomic studies in cucurbits.     

Developmental and nutritional aspects of chayote (Sechium edule,Cucurbitaceae)

Chayote (Sechiumedule, Cucurbitaceae), a lesser-known member of the gourd family, is gaining in popularity and importance as a food crop worldwide. It is unique among cultivated cucurbits by bearing single-seeded fruits and exhibiting vivipary. Chayote, adaptable to a wide range of climatic conditions, can be grown with relative ease. In addition to its fruits, it yields tender shoots for use as vegetable greens, vines as ornament for fences or as animal fodder, and edible subterranean storage roots. It is worthy of being more widely used because it has good nutritional properties and a firm delectable fruit flesh texture and can be prepared in a variety of ways for consumption. Chayote (Sechiumedule, Cucurbitaceae) ist einer der weniger bekannten Gattungen der Cucurbitaceae, obwohl sie immer mehr populaer und wichtig weltweit als Nahrungsmittel wird. Die Pflanze ist einzigartig unter kultivierten cucurbits wegen ihrer einsamigen Früchte und ausgeschossene Samen innerhalb einer Frucht (vivipary). Chayote, der sich zu abwechselnden Klimabedingungen anpassen kaun, lässt sich leicht anbauen. Zusätzlich zu der geernten Früchten kann man die weichen Triebe als Gemüse verwenden, sowie die Rebstöcke als Hofschmuch oder als Futtermittel verwerten. Ausserdem sind die unterirdischen Wurzeln, die kohlenhydraten speichern können, sind essbar. Die kultivation der Pflanze sollte aufgrund ihrer nahrhaften Bestandteile und ihres schmackhaften Fruchtfleisches, das vielfältig zum Verbrauch zubereitet werden kann, verbreitet werden.     

Molecular characterization of pathogenic Fusarium species in cucurbit plants from Kermanshah province, Iran

Fusarium is one of the important phytopathogenic genera of microfungi causing serious losses on cucurbit plants in Kermanshah province, the largest area of cucurbits plantation in Iran. Therefore, the objectives in this study were to isolate and identify disease-causing Fusarium spp. from infected cucurbit plants, to ascertain their pathogenicity, and to determine their phylogenetic relationships. A total of 100 Fusarium isolates were obtained from diseased cucurbit plants collected from fields in different geographic regions in Kermanshah province, Iran. According to morphological characters, all isolates were identified as Fusarium oxysporum, Fusarium proliferatum, Fusarium equiseti, Fusarium semitectum and Fusarium solani. All isolates of the five Fusarium spp. were evaluated for their pathogenicity on healthy cucumber (Cucumis sativus) and honeydew melon (Cucumis melo) seedlings in the glasshouse. F. oxysporum caused damping-off in 20–35 days on both cucurbit seedlings tested. Typical stem rot symptoms were observed within 15 days after inoculation with F. solani on both seedlings. Based on the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) restriction fragment length polymorphism (RFLP) analysis, the five Fusarium species were divided into two major groups. In particular, isolates belonging to the F. solani species complex (FSSC) were separated into two RFLP types. Grouping among Fusarium strains derived from restriction analysis was in agreement with criteria used in morphological classification. Therefore, the PCR-ITS-RFLP method provides a simple and rapid procedure for the differentiation of Fusarium strains at species level. This is the first report on identification and pathogenicity of major plant pathogenic Fusarium spp. causing root and stem rot on cucurbits in Iran.     

Genetic Analysis of East Asian Grape Cultivars Suggests Hybridization with Wild Vitis

Koshu is a grape cultivar native to Japan and is one of the country’s most important cultivars for wine making. Koshu and other oriental grape cultivars are widely believed to belong to the European domesticated grape species Vitis vinifera. To verify the domesticated origin of Koshu and four other cultivars widely grown in China and Japan, we genotyped 48 ancestry informative single nucleotide polymorphisms (SNPs) and estimated wild and domesticated ancestry proportions. Our principal components analysis (PCA) based ancestry estimation revealed that Koshu is 70% V. vinifera, and that the remaining 30% of its ancestry is most likely derived from wild East Asian Vitis species. Partial sequencing of chloroplast DNA suggests that Koshu’s maternal line is derived from the Chinese wild species V. davidii or a closely related species. Our results suggest that many traditional East Asian grape cultivars such as Koshu were generated from hybridization events with wild grape species.     

Seed traits,nutrient elements and assessment of genetic diversity for almond (Amygdalus spp.) endangered to China as revealed using SRAP markers

Almond (Amygdalus spp.) is one of the most important nut fruits worldwide and its seed has been recognized as a health nutrient supply for human consumption. In this study, we characterized the major seed traits and fruit nutrient elements among four Chinese wild almonds (Amygdalus mongolica Maxim., Amygdalus pedunculata Pall., Amygdalus tangutica Batal., and Amygdalus triloba (Lindl) Ricker.) in addition to commercial two cultivars (Amygdalus communis L.), as well as their genetic diversity and natural variations using SRAP marker, aiming at exploiting valuable traits for breeding new cultivars. Our results show that the wild almond species are rich in crude fat, Ca, Ma, Fe and Zn compared to the cultivars analyzed. Our study also identified a relatively high level of genetic diversity (h = 0.3363, I = 0.5075) among species analyzed as evidenced by fact that 161 out of a total of 162 bands amplified with fourteen SRAP primer combinations reveal polymorphism among species analyzed. AMOVA analysis reveals a high level of genetic differentiation among populations (Φ_ST = 0.4474) but The UPMGA cluster analysis indicates that A. communis and A. mongolica are more closely related. Potential utilization of the wild almond species and their valuable traits for breeding new cultivars is discussed.     

Plant-parasitic Nematode Problems in the Pacific Islands

The Pacific islands have a diverse range of food and cash crops with indigenous and introduced nematode problems. The staple food crops have serious nematode pests, such as Meloidogyne spp. on sweet potato, Hirschmanniella miticausa causing corm rot of taro, and Pratylenchus coffeae and Radopholus sp. producing tuber dry rot of yams. Bananas are infested with P. coffeae or R. similis, citrus with Tylenchulus semipenetrans, rice with Aphelenchoides besseyi, and ginger with Meloidogyne spp. and R. similis. Rotylenchulus reniformis, P. zeae, P. brachyurus, and Helicotylenchus spp. are important on all of these and other crops, such as sugarcane, passion fruit, pawpaw, and cassava. Meloidogyne spp. cause serious damage to local and introduced leaf and fruit vegetables and other crops, such as tobacco, sugarcane, pawpaw, black pepper, and pyrethrum. Many other plant-parasitic genera and species, some undescribed, occur in the Pacific, and there are many islands still to be investigated.     

The cucurbit images (1515-1518) of the Villa Farnesina, Rome

BACKGROUND: The gorgeous frescoes organized by the master Renaissance painter Raphael Sanzio (1483-1520) and illustrating the heavenly adventures of Cupid and Psyche were painted between 1515 and 1518 to decorate the Roman villa (now known as the Villa Farnesina) of the wealthy Sienese banker Agostino Chigi (1466-1520). Surrounding these paintings are festoons of fruits, vegetables and flowers painted by Giovanni Martini da Udine (1487-1564), which include over 170 species of plants. A deconstruction and collation of the cucurbit images in the festoons makes it possible to evaluate the genetic diversity of cucurbits in Renaissance Italy 500 years ago. FINDINGS: The festoons contain six species of Old World cucurbits, Citrullus lanatus (watermelon), Cucumis melo (melon), Cucumis sativus (cucumber), Ecballium elaterium (squirting cucumber), Lagenaria siceraria (bottle gourd) and Momordica balsamina (balsam apple), and two or three species of New World cucurbits, Cucurbita maxima, C. pepo and, perhaps, C. moschata (pumpkin, squash, gourd). The images of C. maxima are the first illustrations of this species in Europe.     

Cucurbit Grafting

Due to limited availability of arable land and high market demand for off-season vegetables, cucurbits (plants in the family Cucurbitaceae) are continuously cultivated under unfavorable conditions in some countries. These conditions include environments that are too cold, wet, or dry, or are cool low-light winter greenhouses. Successive cropping can increase salinity, the incidence of cucurbit pests, and soilborne diseases like fusarium wilt caused by Fusarium spp. These conditions cause various physiological and pathological disorders leading to severe crop loss. Chemical pest control is expensive, not always effective, and can harm the environment. Grafting can overcome many of these problems. In fact, in many parts of the world, grafting is a routine technique in continuous cropping systems. It was first commonly used in Japan during the late 1920s by grafting watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] onto pumpkin [Cucurbita moschata Duchesne ex. Poir] rootstocks. Soon after, watermelons were grafted onto bottle gourd [Lagenaria siceraria (Molina) Standl.] rootstocks. This practice helped control declining yield due to soilborne diseases. China produces more than half the world's watermelons and cucumbers (Cucumis sativus L.), and approximately 20% of these are grafted. Use of rootstocks can enhance plant vigor through vigorous attainment of soil nutrients, avoidance of soil pathogens and tolerance of low soil temperatures, salinity, and wet-soil conditions. The type of rootstock affects cucurbit plant growth, yield, and fruit quality. Cucurbit grafting is rare in the United States, but with continued loss of quality disease-free farmland along with the phase-out of methyl bromide, the U.S. cucurbit industry sees grafting as an attractive option. Some seed companies now offer watermelon transplants grafted onto squash or bottle gourd rootstocks, and some transplant facilities offer grafting services. There have been thorough analyses of cucurbit grafting in other countries, but the literature in English is limited. This review summarizes the state of the cucurbit grafting industry on a global level, translating work published in many languages.     

中国长春瓜类白粉菌Podosphaera xanthii形态学和分子系统学研究

2009年长春农博园瓜类白粉病大发生,而且大量闭囊产生在葫芦科的四个属（葫芦属、黄瓜属、栝楼属、南瓜属）植物上。对病害发生的严重度和病情指数进行了调查,结果表明园中栽培的所有品种均为感病品种。形态学观察显示分子孢子串生,具纤维体,闭囊壳只含有一个子囊,内含8个子囊孢子,子囊顶端孔较宽（15.6－28.8μm）。有性和无性形态学特征表明该菌应属于Podosphaera xanthii。基于rDNA ITS序列的分子系统学分析表明该菌与GenBank中已报道的该种在其他地区瓜类上的序列以及在其他寄主上的序列聚     

Cell number regulator genes in Prunus provide candidate genes for the control of fruit size in sweet and sour cherry

Striking increases in fruit size distinguish cultivated descendants from small-fruited wild progenitors for fleshy fruited species such as Solanum lycopersicum (tomato) and Prunus spp. (peach, cherry, plum, and apricot). The first fruit weight gene identified as a result of domestication and selection was the tomato FW2.2 gene. Members of the FW2.2 gene family in corn (Zea mays) have been named CNR (Cell Number Regulator) and two of them exert their effect on organ size by modulating cell number. Due to the critical roles of FW2.2/CNR genes in regulating cell number and organ size, this family provides an excellent source of candidates for fruit size genes in other domesticated species, such as those found in the Prunus genus. A total of 23 FW2.2/CNR family members were identified in the peach genome, spanning the eight Prunus chromosomes. Two of these CNRs were located within confidence intervals of major quantitative trait loci (QTL) previously discovered on linkage groups 2 and 6 in sweet cherry (Prunus avium), named PavCNR12 and PavCNR20, respectively. An analysis of haplotype, sequence, segregation and association with fruit size strongly supports a role of PavCNR12 in the sweet cherry linkage group 2 fruit size QTL, and this QTL is also likely present in sour cherry (P. cerasus). The finding that the increase in fleshy fruit size in both tomato and cherry associated with domestication may be due to changes in members of a common ancestral gene family supports the notion that similar phenotypic changes exhibited by independently domesticated taxa may have a common genetic basis.     

Medieval History of the Duda’im Melon (<Emphasis Type="Italic">Cucumis melo</Emphasis>, Cucurbitaceae)

Medieval History of the Duda’im Melon ( Cucumis melo , Cucurbitaceae). Melons, Cucumis melo, are a highly polymorphic species for fruit characteristics. The melons that are the most valued are the ones that turn sweet when ripe, including the muskmelons, cantaloupes, and casabas. Others, including the elongate adzhur, conomon, and snake melons, are consumed when immature, like cucumbers. The duda’im melons, Cucumis melo Duda’im Group, are special, as their small, spherical, thin-fleshed, insipid but beautifully maroon, dark-orange, or brown-and-yellow striped ripe fruits are valued for ornament and especially for their lush fragrance. The distinctive properties of duda’im melons are matched with special names given to them in several languages and geographical areas, which have made possible tracing of the history of these melons to mid-9^th century Persia. From that region, duda’im melons diffused westward, likely facilitated by Islamic conquests, reaching North Africa and Andalusia in the 10^th century.     

Influence of plant domestication on plant-pollinator interactions: Floral attributes and floral visitor communities in wild and cultivated squash plants

Premise

Domestication of plant species results in phenotypic modifications and changes in biotic interactions. Most studies have compared antagonistic plant-herbivore interactions of domesticated plants and their wild relatives, but little attention has been given to how domestication influences plant-pollinator interactions. Floral attributes and interactions of floral visitors were compared between sister taxa of the genus Cucurbita (Cucurbitaceae), the domesticated C. moschata, C. argyrosperma ssp. argyrosperma and its wild progenitor C. argyrosperma ssp. sororia in the place of origin.

Methods

We conducted univariate and multivariate analyses to compare floral morphological traits and analyzed floral reward (nectar and pollen) quantity and quality between flowers of wild and domesticated Cucurbita taxa. Staminate and pistillate flowers of all three taxa were video recorded, and visitation and behavior of floral visitors were registered and analyzed.

Results

Most floral morphological characteristics of flowers of domesticated taxa were larger in both staminate and pistillate flowers. Staminate and pistillate flowers presented distinct correlations between floral traits and integration indices between domesticated and wild species. Additionally, pollen quantity and protein to lipid ratio were greater in domesticated species. Cucurbit pollen specialists, Eucera spp., had the highest probability of visit for all Cucurbita taxa.

Conclusions

We provide evidence that floral traits of domesticated and wild Cucurbita species experienced different selection pressures. Domesticated Cucurbita species may have more resources invested towards floral traits, thereby increasing attractiveness to pollinators and potentially plant reproductive success. Wild ancestor plant populations should be conserved in their centers of origin to preserve plant-pollinator interactions.