Plant Height (PHE)

In varieties, the mean comparison test (Tukey, 0.05) indicated three groups for this variable, where the highest PHE occurred in the Mulata variety (without pruning) with 230.8 cm, followed by the Patriota variety with 213.9 cm and the lowest growths in height were for the Reina Roja variety (control) with 188.8 cm and the Estrella Costeña variety with 192.1 cm and its absolute control with 192.1 cm (Table 2).

Regarding factor b (pruning), the highest PHE was obtained with pruning at 107 das with 203.3 cm, followed by PHE of 192.7 cm with pruning at 70 and 90 das (Table 2). Apical pruning stopped the growth of the main stem of plants and the size of each variety with its intrinsic characteristics, the height of the varieties would be expected to decrease compared to the same unpruned varieties; however, pruning stimulates the formation of lateral branches, which, in several cases, exceed the main stem, hence the plants appear taller when they have been pruned than when they were not. In addition, plants compete for sunlight, which directly affects their production as it is a photoperiod plant (^{Chavarría, 2012}).

Diameter at the base of the stem (DBS)

In the factor varieties, Mulata reached the highest DBS with 2.1 cm, followed by Patriota (unpruned) with 1.97 cm, in group three the var Patriota (with pruning) had 1.91 cm, followed by the var Mulata (without pruning) with 1.9 cm, the lowest DBS corresponded to the varieties Estrella Costeña and its control (unpruned) with 1.6 cm (Table 2). These results are similar to those reported in Cuba, in six sowing densities of roselle flower, where the ranges of the DBS were very similar, since in high densities the DBS was from 1.89 to 2.18 cm and low densities from 1.83 to 2.15 cm (^{Terán and Soto, 2004}).

Number of branches

In relation to the varieties, the largest number of branches occurred in the var Mulata (with pruning) with 11 branches plant^-1, followed by the varieties Patriota (with pruning) and Estrella Costeña (with pruning), with 8.5 and 8.2 branches plant^-1, respectively. The lowest number of branches occurred in the unpruned treatments, which corresponds to the Reina Roja variety (without pruning) and the Estrella Costeña variety (without pruning) with 6.9 branches plant^-1, respectively (Table 2). This indicates that pruning stimulated the formation of branches.

Regarding the pruning dates, the highest number of branches was obtained when pruning was carried out at 90 das, with 10.6 branches plant^-1 on average, while the lowest data were obtained in the control, which was the treatment without pruning with 7.1 branches plant^-1 and at 107 das with 6.9 branches plant^-1 (Table 2), which reflects that if pruning is done very late, the roselle plant does not develop more branches due to its photoperiod condition, that is, short days occur and the plants begin to form flower buds, without time for more vegetative buds to form.

Yield of fresh calyxes (kg ha^-1)

For varieties, Mulata with pruning reached a yield of 5 182.5 kg ha^-1, followed by the absolute control (unpruned) with 5 175.6 kg ha^-1 and the local variety Reina Roja with pruning, which had 5 088.2 kg ha^-1. The lowest yields correspond to the Estrella Costeña, Mulata and Patriota varieties, the three without pruning with 3 524.4, 3 370.6 and 3 276.3 kg ha^-1, respectively (Table 2). Regarding the factor pruning, the best yield of fresh calyxes occurred when apical pruning was carried out at 90 das with 6 267.2 kg ha^-1, followed by pruning at 70 das with 4 612.5 kg ha^-1 and the lowest yields occurred in the pruning carried out at 107 das, and in the absolute control of the local variety Reina Roja without pruning with 3 999.1 and 3 861.7 kg ha^-1, it was confirmed that pruning can contribute to the increase in roselle production, but it must be done in an appropriate time, in this case, 90 das is recommended, since if it is done very late, it will not contribute to the yield (Table 2).

In this regard, ^{Escobar (1997}) indicates that, when the topping is carried out in roselle plants, they show an immediate response to the breaking of apical dominance, lateral growth is stimulated and the diameter of the foliage increases, therefore, there is a greater area of production of flower buds and an increase in the production of calyxes. For their part, ^{Hidalgo and Cano (2007}) mention that, when apical pruning is carried out at 75 das, there is a significant difference in the increase in the rate of return of the crop, apical growth stops and branching is promoted, which translates into a higher yield of roselle calyxes.

Regarding yield, ^{Cano (2008}) states that topping significantly benefits the yield of calyxes, where the highest production was recorded at 75 das. The results obtained in this study with pruning at 90 das showed the highest yield of fresh calyxes in the Mulata, Reina Roja, Estrella Costeña and Patriota varieties. In addition, ^{Terron (2015}) indicates that topping benefits and accelerates fruiting and in herbaceous crops, it favors the evolution to flower of certain axillary buds or formation of more abundant and uniform buds, as happened in this case.

Yield of dry calyxes (kg ha^-1)

The best yield occurred in the Mulata variety with 1 159.6 kg ha^-1, followed by Estrella Costeña with 1 1107.3 kg ha^-1, Reina Roja and Estrella Costeña (without pruning) with 992.3 and 979.4 kg ha^-1, respectively. The lowest yields occurred in the Patriota variety with pruning and without pruning with 775.2 and 585.6 kg ha^-1, respectively, with an increase in yield of 41% compared to the highest yield shown by the Mulata variety (Table 2).

In the factor pruning, the best yield was obtained when the apical pruning was performed at 90 das with 1 372.5 kg ha^-1, followed by pruning at 107 das with a yield of 946.6 kg ha^-1, the lowest yields occurred in the absolute control (unpruned) and at 70 days with 837.9 and 706.7 kg ha^-1, respectively, which represents a higher yield of 44%, when pruning at 90 das (Table 2). According to the reports of ^{SIAP-SADER (2022)}, in 2019 in Michoacán, the yield ranged between 290 and 870 kg ha^-1, with an average of 580 kg ha^-1 of dehydrated roselle and the one reported at the national level which is 430 kg ha^-1. Undoubtedly, agronomic practices contribute to improving the production of any crop, in this case the use of improved varieties (Mulata) and the control Reina Roja, as well as topping at 90 das showed the best results. For their part, ^{Slamet et al. (2013}) indicated that apical pruning influenced the increase in diameter, as well as the fresh and dry weight of the calyx, in addition, an increase in the content of anthocyanins was obtained.

Effect varieties*pruning

Table 3 shows the interactions between factors a*b in plant height, stem diameter, number of branches, and fresh and dry calyx yield per hectare. The Mulata variety and pruning at 90 das showed the best combination between factors a*b, in the variables number of branches (12.9), weight of fresh calyxes (6 763.2 kg ha^-1) and weight of dry calyxes (1 623.1 kg ha^-1) (Table 3).

The application of topping influenced the yield of the calyxes in fresh and dry weight, which is directly related to the other variables recorded, such as plant height and number of branches; of these variables, the number of branches per plant was the one that was most related to yield, according to the data obtained. The four roselle varieties evaluated responded positively to pruning at 70, 90 and 107 das, and if it is not carried out it, calyx production is low (Figure 1).

Figure 1 Number of branches plant^-1 in four roselle varieties, with pruning and without pruning. 

In this study, pruning at 90 das was the best time to increase yield in the production of roselle calyxes (Figure 1). This practice is important, and its use is recommended in the production of roselle from Bajo Balsas in Michoacán because it favors the formation of branches and flower buds. ^{Escobar (1997}); ^{Farizatul et al. (2016}) mention that this practice generates a response of greater area of production of flower buds, therefore, increases the production of calyxes. In addition, ^{Rojas (2005}) points out that, when the plant reaches 1.5 m in height, pruning is done to make the harvest easier for the cutter, because the roselle flowers are available at a better height.

In the interaction of pruning dates with dry calyx yield, it was observed that, at 70 das, there is a reduction in yield in all varieties, suggesting that early prunings are favorable to increase yield, on the contrary, at 90 and 107 das, an increase in yield was observed, with better results at 90 das with the Mulata and Estrella Costeña varieties, where yields of 1 623.1 and 1 546.9 kg ha^-1, respectively, were obtained (Figure 2). ^{Pal (2018}) observed 25 branches plant^-1 and basal diameter of 4.6 cm with genotypes from India, where there is likely to be greater diversity than that detected in Mexico (^{Rubio, 2016}). Therefore, and according to the findings, of the agronomic practices that must be carried out in the cultivation of roselle, topping is fundamental to stimulate the development of vigorous lateral branches (^{MINEP, 2005}). However, most roselle producers in the dry tropics region of the state of Michoacán do not do it, basically due to ignorance. This means that the yields obtained are low and the productive potential of roselle cultivars is not optimized.

Correlations between variables

A positive correlation was detected between the wet and dry weight of the calyxes per plant and the yield of both weights per ha (r= 0.62^***); that is, the greater the wet weight obtained from the calyxes, the greater the yield of the calyxes in both fresh and dry weight, with a moisture loss between 6 and 10%, which means that, for every 6 to 10 kg of wet calyxes, 1 kg of dry calyxes is obtained. It is opportune to generate information and that it be used to increase the yields of roselle that producers currently obtain, therefore, a greater profit margin would be obtained for families. Given the climatic conditions of the dry tropics region of the state, the crop is a good alternative for producing in marginalized areas, where other crops do not thrive.

Figure 2 Interaction of the yield of dry calyxes of four roselle varieties and three pruning dates. 

Likewise, it is important to specify other management practices to improve the productivity and profitability of the crop and that together contribute to obtaining better yields than those currently obtained in the study area and in other roselle-producing areas. These improvement practices can be determining the best sowing density, sowing dates, optimal fertilization, among others.