| POSTHARVEST BIOLOGY AND TECHNOLOGY HORTSCIENCE 51(9):1127–1133. 2016. doi: 10.21273/HORTSCI10883-16 of S. muricatum. Most importantly, these authors confirmed that the center of origin Solanum and diversity of pepino is Northern Ecuador/ A Review of Pepino ( Southern Colombia, and that pepino is closely related to species of the Caripensia muricatum Aiton) Fruit: A series (Blanca et al., 2007). Pepinos have been commercially and Quality Perspective experimentally grown in several countries, including Australia (El-Zeftawi et al., 1988), Carolina Contreras, Mauricio Gonzalez-Ag uero,€ and Bruno G. Defilippi1 Chile (Bravo and Arias, 1983), Colombia Instituto de Investigaciones Agropecuarias, INIA-La Platina, Unidad de (Ruiz and Nuez, 1997), Peru, Ecuador (Bravo Postcosecha, Santa Rosa 11610, Santiago, Chile and Arias, 1983), Israel (Levy et al., 2006; Schaffer et al., 1989), New Zealand (Heyes Additional index words. Solanaceae, quality, breeding, storage potential, climacteric, flavor et al., 1994; Redgwell and Turner, 1986), Abstract Turkey (Kola et al., 2015), United States . Many attempts have been made to introduce pepinos in several countries. These (Ahumada and Cantwell, 1996), and Spain efforts have involved breeding programs designed to adapt pepino plants to the respective (Rodríguez-Burruezo et al., 2004b, 2011; climates and consumer preferences. However, low yields and the relatively small amount of Ruiz and Nuez, 1997; Ruiz et al., 1997), information on the crop have played a negative role for the expansion of the pepino. where cultivars have been developed for Information on other features of the fruit (e.g., quality, physiology, and sensory attributes) is a Mediterranean climate. also scarce. Only a few studies provide useful data on pepino handling and storage potential; For Chile, the cultivated surface is un- hence, there is not an adequate postharvest strategy to store this species. The objective of known, but the latest census data on planted this review is to provide and discuss the available literature, with an emphasis on farms reported 634 ha of pepino with the postharvest physiology aspects, and present 1) breeding for quality and how this has led specific geographic area for this crop in the to the development of the cultivars known today, 2) fruit physiology and quality, 3) handling IV Region of Coquimbo (North of Chile) and physiological disorders of pepino, and 4) highlight challenges for future research. (ODEPA, Census of Agriculture, 2007). Production is mainly destined for the do- mestic market, and no export records are The pepino (Solanum muricatum Aiton), (Rodríguez-Burruezo et al., 2011). Unfortu- kept. There are currently no registered which is also referred to as pepino dulce in nately, pepino studies in the area of origin are cultivars in Chile, although characteristic Spanish, has been described as a succulent, scarce, and some reasons may lie in the fact that types are distinguished by fruit characteris- juicy, and sweet fruit that is used mainly in pepino is classified as a secondary fruit (Lizana tics and/or by regions where pepinos are desserts, although some cultivars have been and Levano, 1977), exotic or nontraditional grown (Bravo and Arias, 1983). In general, used in salads due to their higher acidity crop, it has a low cultivated surface leading to clonal propagation by cuttings is the only content and grassy flavor notes (Rodríguez- reduced product availability in markets, and an mean of reproduction. This is also recom- Burruezo et al., 2004a, 2011). In the 1990s, insignificant economic importance relative to mended for the cultivars released by Spain pepino was proposed as a physiological other major crops. and other breeding programs, where each model of the texture or firmness changes that The aim of the present review is to cultivar must be vegetatively propagated by occur during maturation and ripening (Heyes critically summarize information of past stem cuttings to maintain the characteristics et al., 1994), and in recent years, research has and recent years on pepino breeding and (Prohens et al., 2002; Rodríguez-Burruezo focused on genetic improvement of fruit postharvest physiology. In particular, re- et al., 2004b). Although the plant is a pe- quality (Levy et al., 2006; Rodríguez- search experiences about storage potential rennial shrub, it is grown annually due to Burruezo et al., 2004b, 2011). The pepino and quality are discussed. its frost sensitivity. Additionally, the plant fruit is a diploid (2n = 24) subtropical species is moderately tolerant to salinity (Ruiz and and is also known as melon pear, melon Nuez, 1997) and grows well under poor shrub, or sweet cucumber. Native species Pepino Crop soil conditions (Bravo and Arias, 1983) from South America, more specifically from The first documented use of S. murica- (Fig. 2). However, pepino plants are sen- the Andes area of Peru and Chile, is widely tum is cited on pre-Inca ceramics displaying sitive to high temperatures, particularly distributed from Colombia to Bolivia (Daunay images of the fruit that date to at least 2000 during pollination and fruit setting (Burge, et al., 1995) (Fig. 1). The pepino fruit served as years ago (Anderson et al., 1996). These 1989). an important crop in Pre-Columbian Andean authors also found that several unique hap- One of the main problems of pepino fruit cultures, and it is a member of the Solanaceae lotypes come from Colombia, suggesting is its low organoleptic quality, which does family, which includes several important crops, that Colombia is the center of origin, based not meet consumer standards as a result such as tomatoes (S. lycopersicum), potatoes on the presumption that diversity is associ- of poor handling and inadequate storage (S. tuberosum), and eggplants (S. melongena) ated with the genetic origin. Therefore, treatments (Huyskens-Keil et al., 2001; among others (Prohens et al., 1996). Of the Anderson et al. (1996) hypothesized that Rodríguez-Burruezo et al., 2011). Very few 1500 species described in the Solanum although the progenitor(s) is/are likely ex- studies report harvest indices. For example, genus (Weese and Bohs, 2007), pepino is tinct, the closest wild ancestors are Solanum El-Zeftawi et al. (1988) recommend that one of the few that is domesticated and caripense and Solanum tabanoense because pepinos should be golden yellow in color, cultivated for food purposes (Daunay et al., they are also found in Colombia and are both with a firmness of 2 kg·cm–2, 40% juice, and 1995). haplotype-associated with S. muricatum. 9°Brix. Today, consumers are more informed Interestingly, most pepino research has been Later, Blanca et al. (2007), by taking advan- and interested in the consumption of exotic conducted in New Zealand, Spain, and Israel tage of more sophisticated genetic tools, fruits of high nutritional value (Rodríguez- through their respective breeding programs concluded that S. muricatum is a compli- Burruezo et al., 2011). For example, pepino is cated cultigen and suggested that several described as a fruit with high water content wild species contributed to its origins and (92% fresh weight) and with excellent anti- Received for publication 22 Apr. 2016. Accepted evolution. Part of the haplotype richness of oxidant properties; therefore, pepino is rec- for publication 22 July 2016. the pepino may be attributed to hybridiza- ommended for diabetic and sugar-free diets We gratefully acknowledge the financial support of tions that occurred at several places and due to its low sugar content. Thus, pepino CONICYT-Chile (Fondecyt project 3150082). times, and to a lack of genetic and geographic has a great potential for use as a natu- 1Corresponding author. E-mail: bdefi[email protected]. barriers between cultivated and wild species ral antioxidant and beyond its nutritional HORTSCIENCE VOL. 51(9) SEPTEMBER 2016 1127 the early 1990s (Ruiz et al., 1992). As a result, into relatively high amplified fragment length two commercial pepino cultivars for the polymorphism (AFLP)-estimated genetic dis- Mediterranean climate, ‘Sweet Long’ and tance and high heterozygosity (Rodríguez- ‘Sweet Round’, were developed as clone Burruezo et al., 2011). In other countries, such selections from seeds from northern and cen- as Israel, lesser-known cultivars have been tral Chilean accessions (Ruiz et al., 1997). developed. The breeding program in Israel Both cultivars were commercially cultivated in released the following cultivars Pepo (the most Spain, and their fruit were exported to several widely cultivated cultivar in Israel), Becky, European countries. Thereafter, through the Rosy, Hannah, Nitza, and Tally (Levy et al., same breeding program, Spain selected hy- 2006). Although this program is not as exten- brids with elevated levels of ascorbic acid, sive as the Spanish breeding program, the high firmness for increased resistance to bruis- authors confirmed an improvement in quality ing, round to ovoid fruit shapes (Prohens and traits (flavor and appearance) by breeding. Fig. 1. Pepino fruit at three different maturity Nuez, 1999), a crispy texture, and low sugar Noteworthy, the authors found no correlation stages. Green (top), white (center), and yellow content for use in salads, as in the case of cv. between high SSC and flavor acceptance. Other (bottom) ground color. Puzol (Prohens et al., 2002). pepino cultivars mentioned in the literature are Other breeding studies have indicated that listed in Table 1; unfortunately, the breeding pepino presents high genotypic variation, programs for some cultivars are unknown or confirming that the pepino is a highly vari- not mentioned. Other pepino cultivars that able species. In addition, dramatic pheno- are briefly mentioned in the literature include typic variations exist among pepino cultivars ‘Lincoln Long’, ‘Golden Litestripe’, ‘Schmidt’ and ecotypes. Contrary to tomatoes, this (Prohens et al., 1996), ‘Lima’, ‘Otavalo’, and phenotypic variation is correlated with a high ‘Quito’ (Prohens et al., 2002). variation at the molecular level, as demon- As for Chile, Munoz~ et al. (2014) recently strated by phylogeny studies (Anderson et al., reported a study based on the physiological 1996; Rodríguez-Burruezo et al., 2003).