Statistical analysis

The analysis of variance showed that there were highly significant statistical differences between concentrations, for the total of harvested fruits (TFC) and the accumulated fresh weight of fruit (PFAF), and significant for total accumulated fruits (FAT) (Table 1), not so for other components of yield, such as number of accumulated clusters (NRA), polar diameter (DPO) and equatorial (DEC) of the fruit, accumulated dry weight of fruit (PSAF), dry weight per fruit (PSxF) and fresh weight per fruit (PFxF) (Table 1).

The components of yield that had high coefficients of variation were number of accumulated clusters, total accumulated fruits and accumulated fresh weight of fruit (Table 1), this could be due to the fact that the evaluated plants presented some degree of genetic variation. According to the above, ^{Gutiérrez et al. (2011)} indicate that the cuatomate (Solanum glaucescens Zucc.), is a plant in process of domestication.

Number of bunches. The four treatments of the Steiner solution applied to cuatomate, did not generate significant statistical differences between these treatments for the number of clusters accumulated during the five cuts. However, the results show a higher number of bunches in the highest concentrations of the nutrient solution (Figure 2), with 75 and 100%, with 6.7 and 6.5 bunches on average, respectively, during the days evaluated. Regarding ^{Moreno et al. (2005)}, applied a nutritious mother solution in the tomato (Solanum lycopersicum) crop which increased the number of bunches on average per plant (4 bunches), then the plants treated with vermicompost mixtures plus sand.

Figure 2 Number of clusters of cuatomate (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 5.05). 

In the present study, the Steiner nutrient solution at 75 and 100% registered a higher number of average clusters per plant (5.7 and 5.5 clusters) than the one obtained by ^{Moreno et al. (2005)}. In addition, in the study by ^{Moreno et al. (2005)} used freshly germinated tomato plants fertilized with the mother solution containing the nutrients necessary for their development, while in the present study one year old growth plants were used that were fertilized with the Steiner nutrient solution containing the necessary nutrients for the development of cuatomate.

On the other hand, ^{Carrillo et al. (2003)} found, for Lycopersicon esculentum Mill., Under controlled greenhouse conditions, a positive correlation for the number of bunches, with respect to yield, which indicates that the higher the number of bunches, the higher the yield. In addition, he mentions that temperature is an important factor that influences the number of bunches harvested, grown under these conditions.

Number of total accumulated fruits. The plants to which the high Steiner nutrient solution was applied (75 and 100%) presented the highest number of accumulated fruits, with 75 and 59 (Figure 3). This may be due to greater availability of nutrients in the nutrient solution. With these results increasing the concentration of the Steiner nutrient solution increases the number of bunches and in turn the number of fruits accumulated.

Figure 3 Number of cumulated total fruits of cuatomate (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 44.731). 

In this regard, ^{Maldonado et al. (2016)} reported 33 fruits per tomato plant (Solanum lycopersicum L.), open-pit, with the Steiner solution at 25%, while in the present study 30 fruits were recorded on average per plant of cuatomate (Solanum glaucescens Zucc.) Under shade mesh, fertilized with 25% Steiner nutrient solution, which indicates that S. glaucescens grown under these conditions produces more fruits.

In another solanaceous (Capsicum annuum L.), the highest number of fruits was found in high concentrations of Steiner nutrient solution (75, 100 and 125%) and the lowest number of these in the concentration at 25% (^{Valentín et al., 2013}). What coincides with the present study where the higher the concentration, the greater the number of fruits obtained from the cuatomate (S. glaucescens). The same effect is reported by ^{Lima et al. (2014)}, who when applying different concentrations of nitrogen and phosphorus, in the form of ammonium sulfate and superphosphate, found answers in high doses, where the number of fruits in the Solanum melogena L. crop increased.

Polar diameter of fruit. There was no effect of Steiner nutrient solution concentrations on the polar diameter of the fruit of S. glaucescens (3.81 to 4.06) (Figure 4), but this polar diameter was higher than that reported by ^{Vargas (1998)} who evaluated a sample of 211 commercial fruits of cuatomate, and found that the polar diameter ranged from 3.65 to 3.69 cm. In addition to other Solanum species, the cuatomate fruits harvested in this investigation have a greater polar diameter than Solanum uncinellum (1.2 to 2.7 cm) reported by ^{Benítez et al. (2011)}. On the other hand, for another solanaceous such as Physalis pruinosa, with the application of algae-based nutrients the polar diameter of green-yellow fruit was 11.57 mm (^{García et al., 2015}).

Figure 4 Polar diameter of cuatomate fruit (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 0.26 cm). 

Equatorial diameter of fruit. Like the polar diameter of the fruit, there was no effect of the concentrations of the Steiner nutrient solution on Solanum glaucescens Zucc., registering fruit of 3.92, 3.83, 3.95 and 4.0 cm of equatorial diameter of the fruit with 25, 50, 75 and 100% Steiner nutrient solution (Figure 5). ^{Vargas (1998)} collected commercial fruits of cuatomate in the Mixteca Baja Poblana region, in which he found equatorial diameters that varied from 4.10 to 4.12 cm, these diameters indicate that they were slightly higher in the fruits harvested in the solutions at 25, 50 and 100 % and similar with concentration of 75% of the present study (Figure 5). In addition, this same author, of the long/wide relation of the fruit, found that 78% were spherical, while the rest (22%) were slightly oval. In turn, it also reports the absence of channels and curvatures along these.

Figure 5 Equatorial diameter of cuatomate fruit (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 0.3 cm). 

On another species of Solanum, ^{Maldonado et al. (2016)}, reported 4.7 cm of equatorial diameter of Solanum lycopersicum L., with a 25% Steiner nutrient solution, which was greater than the equatorial diameter of S. glaucescens (3.92 cm) with the same 25% Steiner solution of the present study. Similarly in another solanaceous ^{Rojas et al. (2008)} report the apple-tree chile (Capsicum pubescens R and P), sampled for two years, a fruit width of 4.8 and 4.1 cm with Steiner nutrient solution at 75%, so that the fruits of cuatomate have a smaller width (3.95). cm) treated with the same concentration of Steiner nutrient solution at 75%, compared to the fruits of C. pubescens.

Total number of harvested fruits. All the plants treated with concentrations of Steiner nutrient solution presented fruits of commercially acceptable size and color, but there was an effect of these concentrations on the number of harvested fruits, where at a higher concentration of the Steiner nutrient solution (25, 50, 75 and 100%), the greater the number of fruits harvested per plant (15, 17, 24 and 32 fruits, respectively) (Figure 6).

Figure 6 Total number of fruits harvested cuatomate (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 10.9). 

Similarly, ^{Gastelum et al. (2013)} evaluated the same concentrations of the Steiner nutrient solution (25, 50, 75 and 100%) on another solanaceous Physalis peruviana L. and these authors concluded that the yield of the crop was affected by the concentration of the Steiner nutrient solution. An increase was observed when increasing the concentration of the solution, obtaining 110 fruits per plant with 100% of Steiner’s nutrient solution, while in the present study, at the same concentration of the Steiner solution, 32 fruits of cuatomate were harvested. On the other hand, ^{Valentín et al. (2013)} found that at higher osmotic concentrations of Steiner nutrient solution applied to water chili (Capsicum annuum L.), under protected conditions and hydroponics, the number of fruits increased, reaching 100 fruits per plant with an osmotic concentration of 0.09 MPa of Steiner nutrient solution.

Accumulated total fresh weight of fruit. For S. glaucescens grown under shade and hydroponics, increasing the concentration of the Steiner nutrient solution increased the fresh weight of the cuatomate and therefore reflected in higher yield, recording accumulated average weights of 300.25, 363.0, 533.25 and 706.75 g per plant at 25, 50, 75 and 100% Steiner nutrient solution (Figure 7).

Figure 7 Cumulative fresh weight of cuatomate fruit (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 278.62 g). 

This is also observed in another solanaceous such as “water chili” (Capsicum annuum L.), where solutions with high concentrations were those that presented higher yield than those with lower concentrations (^{Valentín et al., 2013}). Or, Physalis ixocarpa Brot., Cultivated under different concentrations of nutrients, the production of fruit increased, according to the availability of nutrients, where the 75% solution reached the maximum production of fruits per plant (3 kg per plant), but from that point the production of fruits per plant decreased (^{Castro et al., 2000}).

The use of nutritive solutions with different concentrations has been used in other crops with similar results, such as Capsicum pubescens R and P (^{Pérez and Castro, 2010}) and thyme (Thymus vulgaris L.) (^{Guerrero et al., 2011}).

Accumulated dry weight of fruit. Between the concentrations of the Steiner nutrient solution the accumulated dry weight of cuatomate fruit is maintained, with 11.26, 10.53, 13.11 and 12.12 g at 25, 50, 75 and 100% of the Steiner nutrient solution (Figure 8). A similar effect was reported for "water chili" (Capsicum annuum L.) using high osmotic potentials in Steinar nutrient solution, under protected conditions, no differences were observed in the accumulation of dry matter in fruit (^{Valentín et al., 2013}).

Figure 8 Accumulated dry weight of cuatomate fruit (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 3.35 g). 

When different concentrations of nutrients are applied to a crop, there may be the possibility that these are directed to different bodies, mainly those of demand, and not to sites of the plant of commercial interest. ^{Peil and Galvez (2005)} indicate that there is interest in that a maximum proportion of assimilated be allocated to the fruits; However, there are limits in the fraction of those assimilated that can deviate from these, since the plants need to allocate a sufficient amount for the other organs.

Dry weight per fruit. Like the accumulated dry weight of fruit, the dry weight per fruit (2.25, 2.1, 2.62 and 2.42 g) does not increase in the cultivation of cuatomate (Solanum glaucescens Zucc.), Evaluated under a shading system and hydroponics with different Steiner nutrient solution concentrations (25, 50, 75 and 100%) (Figure 9). On the other hand, the percentage of dry matter accumulated in fruit of cuatomate was about 11% of the fresh weight of the fruit for the different concentrations of Steiner solution, in comparison with that reported by ^{Peña et al. (2013)} in Solanum lycopersicum, cultivated in greenhouse and hydroponics, found values of 4.5 and 5.4% of fresh weight of fruit, which indicates that the percentages were lower in comparison with the accumulated dry matter of fruits of S. glaucescens Zucc. found in the present study.

Figure 9 Dry weight per fruit of cuatomate (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 0.66 g). 

Fresh weight per fruit. The harvested fruits of cuatomate (Solanum glaucescens Zucc.) presented similar fresh weights (between 20 and 23 g, approximately) in plants treated with nutrient solution Steiner at 25, 50, 75 and 100% (Figure 10). In a previous study, the plants of cuatomate registered an average weight of 12.27 g of fresh fruit weight, large fruits (30 g) and boys (5.87 g), both from two municipalities (Tehuitzingo and Izúcar of Matamoros) (^{Vargas, 1998}), which indicates that the fruits obtained under these conditions in the cultivation of cuatomate have higher average weights than those obtained by this author.

Figure 10 Fresh weight of cuatomate fruit (Solanum glaucescens Zucc.) grown under shade mesh in Atlixco, Puebla, 2016 (Tukey p ≤ 0.05; 3.77 g). 

On the other hand, ^{Gastelum et al. (2013)} report that as the concentration increases from 25 to 50 and 75% Steiner solution increases the weight of the fruit of gooseberry (Physalis peruviana L.), but this weight of the fruit decreases to 100% of Steiner solution, except in plants with density of 8 plants per m, where the highest weight of cuatomate fruits was recorded. In contrast, in the present study increasing the concentration of Steiner nutrient solution increased the weight of cuatomete fruits.

^{Muñoz (2009)} points out that excessive applications of nitrogen in tomato in greenhouse, increase the possibility of appearing a ripening disorder in the fruit, called “green shoulder”, while ^{Castellanos (2009)} indicates that the excess of nitrogen in the crop of tomato (Solanum lycopersicum L.) makes it very vegetative, in addition to appearing in the floral bouquet leaves, characteristic of excess vigor in the plant.

In the present study in cuatomate, this characteristic did not appear in the flowering stage, it appeared after the third cut, when the fruits were harvested in the treatment with 100% concentration of Steiner solution. With all these results, it is necessary to determine the optimum concentration of the nutritive solution to ensure the best fruit weight of the agricultural crops, to avoid that an excess concentration of the fertilization affects the yield of the crop and commercial economic price.