Horticultural Characterization and Biodiversity of Chilacayote
(Cucurbita ficifolia
Bouché), a High-altitude-adapted Squash

Timoteo Valdez-Hernández

Departamento de Fitotechnia, Universidad Autónoma Chapingo, Chapingo, Mexico, 56230, Mexico

Laura C. Merrick

Department of Agronomy, Iowa State University, Ames, IA 50011

Clemente Villanueva-Verduzco

Departamento de Fitotechnia, Universidad Autónoma Chapingo, Chapingo, Mexico, 56230, Mexico

Additional index words. yield, phenology, physiology, squash, summer squash, cold tolerance, landrace, biodiversity, germplasm, Cucurbita ficifolia

Abstract. Cucurbita ficifolia is a squash species adapted for production at high elevation in the tropics. To date it has not been the target of formal breeding programs and consists almost entirely of landraces (locally adapted, traditional cultivars). For Mexico where it is known as chilacayote, two main cultivars are described. The predominant, corriente or common type is grown typically as an intercrop with maize (Zea mays) and used mainly for consumption of mature fruit as a crystallized candy or as fodder for livestock. The other typeknown as the fino or fine typeis restricted to the vicinity of the Chalco region near Mexico City. The fino type was selected by local farmers for intensive commercial production of immature fruit as a fresh market vegetable and is grown either in monoculture or in association with fruit trees. Results of characterization for a number of physiological, phenological and morphological traits shows differentiation between these two cultivar types for yield and certain aspects of plant development.

Cultivation of the squash species Cucurbita ficifolia Bouché in Mexico is characterized by its production in high altitude regions (1400 to 2700 m), tolerance of cool temperatures, and relatively long growth cycle (6 to 8 months). Called the fig-leaf gourd or black-seeded squash in English, but known as chilacayotefrom the Nahuatl name tzilac-ayotli or smooth squashthroughout its range of distribution in Mexico, C. ficifolia is principally a marginal landrace crop grown in milpas or traditionally managed agroecosystems where it is intercropped with maize (Zea mays L.) (Andres, 1990). The fruit of C. ficifolia, with its unusual combination of white flesh and typically black (sometimes tan or dark brown) seeds is unique among domesticated Cucurbita species (Andres, 1990; Whitaker and Bohn, 1950). Mature fruit are the primary product harvested from the type of chilacayote

common to most production regions of C. ficifolia in Mexico. This predominant typedescribed as the corriente or common type (Valdez, 1994)is grown mainly for home consumption or market of the candied fruit flesh (dulce) or used as a forage for livestock (Andres, 1990; Whitaker, 1968). In the vicinity of the Chalco Valley in the states of Mexico and Morelos, local farmers have, however, selected a unique type of chilacayotethe fino or fine type (Valdez, 1994)for intensive commercial production of immature fruit for fresh market as vegetables. Unlike the corriente type, the fino type is grown in monoculture or intercropped with tree fruit such as fig (Ficus carica L.) or peach (Prunus persica L.). Combined with desirable traits noted for the species in generalincluding resistance or tolerance to white flies (McCreight and Kishaba, 1991), resistance to several viruses (Provvidenti, 1990) and its adaptation to cool climates

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(Okimura et al., 1986; Tachibana, 1987)the fino type of C. ficifolia has potential for wider exploitation as a summer squash for high elevation regions in the tropics.

Research summary

Research was initiated in 1993 and 1994 with the objective of characterizing physiological and phenological development and morphological variation as two populations representing the corriente and fino types of chilacayote. The corriente type was obtained in the market in Texcoco in the state of Mexico, while the fino type was obtained from Tetela del Volcan, Morelos. The corriente type was more widespread in habit and produced fruit that were six to seven times heavier than those of the fino type (Table 1). On average the fino type flowered 30 to 40 days earlier, had smaller leaves that were greater in number, produced three times as many flowers and six times as many fruit as the corriente type. The fino type generally possesses a round fruit that averages 1.1 kg. In this type, the onset of female flowering occurred typically 93 days after planting. The corriente type is characterized by an elliptical fruit that averages 7.0 kg. It typically begins female flowering 125 days from planting (Valdez, 1994).

Research conducted during 1995 and 1996 focussed on the effects of plant population density and planting date on production and distribution of fruit of the fino type. Of three plant densities tested (333, 528, and 1650 plants/ha), the highest density resulted in the highest yield of immature fruit (27.7 vs. 31.9 vs. 53.0 tons·ha­1, respectively). The majority (75% to 78%) of mature fruit production occurred in the first two thirds of the plant structure and was most concentrated in branches of the third and fourth order. The number of mature plants produced per plant tends to decrease with late planting (Valdez, 1997).

In 1996, in collaboration with the McKnight Foundation project entitled "Conservation and Improvement of Crop Production in Mexico: A Farmer-Based Approach" (Anonymous, 1994), a study was undertaken of biodiversity of chilacayote derived from two areas of central Mexico (the Sierra Norte de Puebla and the Chalco-

Morelos region). The accessions grown in maize cropping systems (corriente type) originated from 16 localities distributed in a total of eight municipalities (five in Sierra Norte de Puebla and three in Chalco-Morelos). Those from monocrop production systems (fino type) were derived from seven localities representing two municipalities strictly in the Chalco-Morelos region. All accessions originated from altitudes ranging from 1600 to 2500 m, but differences between the types were observed in elevational distribution. All of the 38 fino-type accessions were collected from elevations over 2200 m. In contrast the 35 corriente-type accessions originated from a much wider range of altitudes: 29% from 1600 to 1900 m, 51% from 1900 to 2200 m, and 20% from over 2200 m. Roughly half of the corriente-type accessions from Sierra Norte de Puebla were collected at lower elevation, and about one quarter each from intermediate and high zones, whereas most of those from the Chalco-Morelos region were collected from localities at intermediate elevation.

The performance of chilacayote accessions derived from both types of production systems was evaluated for a variety of characteristics, including number of days to female flowering, number of fruit produced per plant, and color of mature fruit. Among 35 corriente-type accessions, landraces from two localities were identified as better performing than the other corriente accessions by virtue of earliness (female flowers in 96 and 102 days, respectively) combined with relatively high yield of mature fruit per plant (12 to 13 fruit). Three populations of the fino type were found to be outstanding due to their combination of earliness to female flowering (91 to 93 days) with relatively high yield of mature fruit per plant (11 to 19 fruit).

Before this study, extreme earliness and high yield of fruit in corriente-type C. ficifolia landraces was unreported. With these results there is evidence that some corriente-type chilacayote (although low in frequency) are characterized by the earliness and yield potential more typical of the fino type. When classified into three maturity groups based on number of days to female flowering (Group I: < 95 days; Group II: 95 to 109 days; and Group III: > 109 days), 70% of the fino types

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Table 1. Phenological and physiological traits and yield of two types of chilacayote (Cucurbita ficifolia), 1994.

Characterz Fino Corriente

Plant habit (m) 18.9 22.5

Days to emergence 13.6 12.2

Days to first male flower 83.6 121.6

Days to first female flower 92.5 123.5

Days to harvest of immature fruit 100.6 135.4

Days to harvest of mature fruit 214.0 230.4

Accumulated heat units to initial female flowering 859.8 °C 1204.2 °C

Accumulated heat units to immature fruit harvest 928.0 °C 1236.7 °C

Accumulated heat units to mature fruit harvest 1794.3 °C 1857.8 °C

Leaf area (dm2) 6471.1 11968.6

Harvest index 28.2 7.0

Leaf area index 3.91 3.67

No. of leaves 5108.0 5310.0

Dry weight of leaves 6050.0 13590.0

No. of days in vegetative cycle 218 247

No. of days in reproductive phase 155.0 157.0

Dry weight of reproductive structures 5387.8 1315.7

Weight of mature fruit (kg)y 1.0 6.7

Weight per seed (g) 0.04 0.15

No. of male flowers per planty 4762.2 1695.2

No. of female flowers per planty 176.6 64.2

No. of mature fruit per planty 129.8 17.3

No. of immature fruit per plant 922.8 102.4

zAverage of five plants per cultivar type.

yValues from plants from which no immature fruits were harvested.

McCreight, J.D. and A.N. Kishaba. 1991. Reaction of cucurbit species to squash leaf curl virus and sweetpotato whitefly. J. Amer. Soc. Hort. Sci. 116:137­141.

Okimura, M.S., S. Matsuo, and S. Okitsu. 1986. Influence of soil temperature on the growth of fruits and vegetables grafted on different rootstocks. Hort. Abstr. 59:329.

Provvidenti, R. 1990. Viral diseases and genetic sources of resistance in Cucurbita species, p. 427­435. In: D.M. Bates, R.W. Robinson, and C. Jeffrey (eds.). Biology and utilization of the Cucurbitaceae. Comstock Publ. Assoc., Ithaca, N.Y.

Tachibana, S. 1987. Effect of root temperature on the rate of water and nutrient absorption in cucumber cultivars and figleaf gourd. J. Jpn. Soc. Hort. Sci. 55:461­467.

Valdez-Hernández, T. 1994. Características de interés agronómico de dos tipos de chilacayote (Cucurbita ficifolia Bouché) en México [paper presented at the] VI Congr. Nacional Hort., Hermosillo, Sonora.

Valdez-Hernández, T. 1997. Distribución del fruto fisiológicamente maduro en planta de chilacayote (Cucurbita ficifolia Bouché) cultivar fino [paper presented at the] IX Congr. Nacional Hort., Culiacán, Sinaloa.

Whitaker, T.W. 1968. Ecological aspects of the cultivated Cucurbita. HortScience 3:9­11.

Whitaker, T.W. and G.W. Bohn. 1950. The taxonomy, genetics, production, and uses of the cultivated species of Cucurbita. Econ. Bot. 4:52­81.

clustered into the earliest group and all but one of the rest were in the intermediate maturity group (29%). In contrast, the corriente-type accessions were more variable with 27% each in Groups I and III (earliest and latest), and the rest (48%) in the intermediate Group II. The results of the study indicate considerable variation exists among the corriente types in terms of earliness (91 to 138 days to flowering) and number of fruit per plant (from 1 to 13). Within accession variability was observed, especially with regard to earliness. On average, the fino types flowered earlier and were higher yielding, but they also tended exhibit less variability than the corriente types.

Literature cited

Anonymous. 1994. McKnight Foundation awards first grants under new international collaborative crop research program. Diversity 10:39­41.

Andres, T.C. 1990. Biosystematics, theories on the origin, and breeding potential of Cucurbita ficifolia, p. 102­119. In: D.M. Bates, R.W. Robinson, and C. Jeffrey (eds.). Biology and utilization of the Cucurbitaceae. Comstock Publ. Assoc., Ithaca, N.Y.

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