Study area

The study area covers the region between the states of San Luis Potosí (Salinas, Villa de Reyes and Villa de Ramos), Jalisco (Ojuelos, Encarnación de Díaz, Lagos de Moreno) and Zacatecas (Guadalupe, Ojocaliente and La Pendencia Pinos). Field trips were made at each site, around municipal headwaters and preferably in easily accessible sites.

Characteristics of the study area

Four physiographic regions converge in this area: The Northern Upland, in central and northern Mexico; the Southern Highlands, in the south and east, the Lower Sierras, to the northeast and the High Sierras with Valleys, to the west of the area (^{Tamayo, 1981}). There are mountains and plains, with altitudes of 1 000 to 2 600 meters above sea level. (^{Ferrusquia-Villafranca, 1993}) and large areas of alluvium with isolated hills.

The most common substrate in the north of the area is the Cretaceous and Jurassic limestone rocks; igneous rocks, mostly rhyolites and sometimes andesites and basalts, are more common in the south and west. Calcisol-type soils predominate, distinguished by the accumulation of calcium carbonate; in the northeast there are areas of Regosol, shallow soils and low fertility (^{Cuanalo et al., 1989}; ^{Ferrusquia-Villafranca, 1993}).

The predominant climate is the BS, with the variants BS0, the driest and BS1, the least dry (^{García, 1973}). Precipitation is scarce and irregular, with an annual average of 240 to 770 mm (^{Cuanalo et al., 1989}). The average annual temperature varies from 13.5 to 20.5 °C (^{Anónimo, 1980}).

Sample size determination

Prior to the general collection, a pilot sampling was carried out on March 19 and 27, 2014, at two sites: La Cocona, Salinas de Hidalgo San Luis Potosí and Chinampas, Ojuelos Jalisco. With the data obtained, the actual sample size was calculated. The number of plants to be sampled was obtained using the formula of Bolflor et al. (2000). Where: n= number of sampled plants; E= margin of error allowed for this collection; t= value of ‘t’ of student (t= 0.05); N= total population of crazy pumpkin plants in the locality; CV= coefficient of variation; to obtain this value it is necessary to do a pilot sampling.

Descriptors analyzed

In the selected sites, 25 plants were sampled for each of them and data were taken from the following morphological descriptors: in relation to foliage, 1) number (NPG) and length of the guides per plant (LGP) were analyzed, the latter data it was measured in cm from the beginning of the stem to the apex of the last leaf, distance between internodes; and 2) leaves, considering the leaf length (LH), leaf width (AH) and petiole length (LP), measured in units of cm. In relation to the root, the length, amplitude and diameter (cm) and volume expressed in cm³ were determined. For the latter three plants were extracted from each site, which contained 3, 8 and 13 guides.

Indicators to determine the state of development of plants

According to the following figure, the clusters of the crazy zucchini plants were determined.

^{Human (1991)}. Sweet potato descriptors. CIP/AVRDC/IBPGR.

Figure 1 Indicators that allow to identify the state of development of the plant. 

Analysis of morphological data

The data of simple morphological variables were integrated in intervals according to the growth behavior and analyzed by means of comparison of averages between the sites of wild populations.

Grouping of Cucurbita foetidissima Kunt according to morphological components

To perform the grouping by main components, 13 morphological variables of Cucurbita foetidissima Kunth plants were analyzed, integrated into vegetative characters (internode distances, the length and breadth of the leaf, as well as the length of the petiole, number of total guides, the length of the guides), of reproductive development (number of flowers and number of fruits) and of the root (total weight, volume, length, broad width, length).

With the database, a multivariate analysis was carried out based on principal component analysis (ACP) to decrease inference and grouping by similarity to understand the information of groups of plants with similar characteristics, discriminating groups using the minimum internal variance (Ward) to form types of plants, Infostat was used (^{Di Rienzo, 2014}).

Geo-referencing of wild zucchini habitats

In general, the sampled areas were found on roadsides or fields, with a slope between 15 and 45 °C and an altitude of 1 814 and 2 475 meters above sea level. The coordinates, altitude and characteristics of each collection location are mentioned. The plant communities we found were different conditions according to the region and the characteristics of the collection site (Figure 2 and Table 1).

Figure 2 Municipalities where the study of crazy zucchini was carried out. 

Behavior of morphological variables (guides and leaves). In general, in Table 2, the quantitative values of the vegetative growth of a total of 25 plants analyzed in nine plant sites of Cucurbita foetidissima Kunth are indicated. It was observed that there is a great variation in the number of guides per plant (1-19), plants with less than eight guides predominate, the Chinampas Ojuelos plants and, in an outstanding way, the plants located in La Cocona, Salinas de Hidalgo and Yoliatl Ramos Villa. San Luis Potosí showed more guides (9-12) probably at a greater number of years or less favorable climatic conditions (natural requirement of the plant).

In length of guides prepondered those with less than 6.75 m and the longest were found in Guadalupe Zacatecas. In the length of the petiole, those of large-medium size (7.5 to 12 cm) in length predominated, although those of Ojocaliente stood out for greater length, with shallow soils. In leaf size, the plants showed from small to large (16.5 to 27 cm) and in an outstanding way, the Ojocaliente plants. They presented a larger quantity of larger leaves (13.5 to 18 cm).

According to the collection sites, the Chinampas, Ojuelos Jalisco, plants are located mainly on the banks of roads and roads, cohabit with fast-growing pastures and are sometimes ‘pruned roadside’ so that their growth is differentially induced in relation to plants from other sites analyzed.

The plants of La Cocona, Salinas de Hidalgo, San Luis Potosí. They form agglomerated populations with a very short separation between plants (0.5-1 m) so there is high competition for the few water and mineral resources they have. The plants of Encarnacion de Díaz, Jalisco, were found in a pile of gravel roadside, showed several years and did not compete with any weeds, so they have the shortest petiole.

The plants of Guadalupe, Zacatecas, compete with grasses that limit the optimal growth of the squash, so they tend to develop longer petioles so that the leaves get sunlight were found plants such as jaral (Cistus ladanifer), arnica (Arnica angustifolia), brush or ant grass (Pathenium hysterophorus L.), prickly pear (Opuntia spp.), cardenche (O. imbricata) and mesquite (Prosopis laevigata) preferably, indicating a synergy that leads to generally large plants (676 cm).

In Lagos de Moreno Jalisco, the plants develop as “medium plants” (326-475 cm). At the El Centenario site, Villa de Reyes, San Luis Potosí, the climate is wetter so there are few populations of ‘Crazy zucchini’ due to higher grass growth in susceptible places.

In Yoliatl, Villa de Ramos. San Luis Potosí, Cucurbita foetidissima Kunth. It requires little water and grows faster in arid and semi-arid environments (^{Web Academia, 2013}). The plants that develop are located in a cradle of reliefs and cohabit with plants such as the giant (Nicotiana glauca), prickly pear (Opuntia spp.), yucca (Yucca sp.) and very short grass (Boutelova curtipendula) (^{Anónimo, 2016}).

Description of the Cucurbita foetidissima Kunth tubers. In general, the Chinampas (Ojuelos), Encarnación de Díaz and Lagos de Moreno (Jalisco) plants showed intermediate values between the studied regions in their root variables (Table 3).

These showed a weight of 1 615 g, perimeter of 33.8 cm, width of 10.8 cm, length of 52.6 cm, number of guides of 44.5, a volume of 1 690.5 cm³ and fruit content of 162. The above may be due to the fact that the plants they grow in climatic conditions not very favorable to the optimum needs of the plant, since these sites are characterized by warmer climates and with greater precipitation (in Chinampas Ojuelos, 473.5 mm, Encarnación de Díaz 564 mm and Lagos de Moreno 573.2 mm respectively) .

In an outstanding way, the plants of La Cocona (Salinas), Yoliatl (Villa de Ramos) and Centenario (Villa de Reyes) corresponding to the State of San Luis Potosí, showed, on average, the greatest attribute of the root with a weight (2 536 g), perimeter (45.5 cm), amplitude (15.3 cm), length (51.8 cm), number of guides (67), volume of 2 411.2 cm³ and fruit content of 769 (in full).

The factors that can possibly influence ‘this optimal development’ can be the following: higher incidence of solar radiation, little competition with ‘aggressive’ pastures and lower rainfall index (La Cocona Salinas with 391 mm, Yoliatl Villa de Ramos with 429.6 mm and El Centenario Villa de Reyes with 360 mm respectively). The plants with lower attributes in the root variables are found in those in the state of Zacatecas with a weight of 1 248.8 g, perimeter of 25.7 cm, amplitude of 10.3 cm, length 29.1 cm, number of guides of 63.3, a volume of 1 574.1 cm³ and fruit content of 218.

The lower attributes of the root of this area may be due to a higher altitude above sea level, lower annual average temperature, low environmental humidity or because the soils are less fertile or shallow, since rainfall is intermediate between regions studied (La Pendencia, Pinos, 429.6 mm, Guadalupe, 500 mm and Ojocaliente, 500 mm respectively).

Fruits

In the number of fruits per site (Table 3), Yoliatl stood out with 649 fruits in total, followed by Encarnación de Díaz (118) and La Cocona, Salinas de Hidalgo, San Luis Potosí (116). Here we deduce that the climate is an important factor in the pumpkin plants, since we find more fruits in places with less rainfall and greater solar incidence.

The number of fruits per sites is important and complements what was found by ^{Flores (2016}) where he reports that crazy zucchini from these places have 100 seeds weighing 3.70 g and 27 017 seeds per kilogram. On the other hand ^{Flores (2016)} determined that the linoleic and linolenic acids (essential fatty acids) that the seed contains are of great value for possible use as edible oils. According to the above, the most recommended place to collect fruits and seeds is Yoliatl in Villa de Ramos, San Luis Potosí.

Estimate of the development status of Cucurbita foetidissima Kunth populations in relation to morphological characteristics. With the information of the morphological variables analyzed, an estimate was made (Table 4) of the probable development condition presented by the native populations of zucchini, inferring a plant classification according to their size. Thus, generally, Jalisco plants that have a root volume of 1 690.5 cm³ are considered of intermediate size, while that of San Luis Potosí with a root volume of 2 411.2 cm³ plants are considered large in size and finally, the plants of the State of Zacatecas with a root volume of 1 574.1 cm³ are considered small plants.

It is worth mentioning that some plants stood out in guide length (plus 26 m) despite the limited agroclimatological conditions. This classification can be used to propose a way to identify, compare populations, select plants in optimal growth status and complement the morphological variables according to the purpose of agroindustrial use of the plant (fodder, oil, bioenergy, reforestation).

The analysis of the morphological components generated eight groups of plants, determining as the main component, the amplitude of the root with 61% of the variability and the length of the second internode along the guide with 22% of additional variance), which it was divided into two slopes corresponding to the content of number of guides and length of internodes (Table 4 and 5).

The distribution of groups in different regions groups 1 and 6 prevail in almost all populations of crazy zucchini. This is important to quickly and easily locate populations of crazy zucchini in a certain place (Table 5 and 6).