Introduction

The cocoa is native to tropical areas of America (Amazon and Orinoco). Handling was extensive in Mesoamerica, and then intensively cultivated by the Maya in Mexico (^{Mendoza, 2013}). Currently, it is grown in more than 60 countries, global production is concentrated in Africa, Asia, Central, North and South America. Today, more than 20 million people worldwide depend directly on the crop for their livelihoods. Mexico has a close contribute 1% to the world production of cocoa, from 61 168.10 ha, located in four states, with Tabasco and Chiapas the largest producers, generating more than eight million days a year, with a contribution of 27 844.12 t in terms of average performance reported for 2014 it was 0.46 t ha^-1 (^{SIAP, 2014})

The M. roreri plant is the main problem facing cocoa production in Mexico and most countries in Central and South America, this disease causes great losses in the cultivation of cocoa, becoming up to 100% if weather conditions are favorable and trees are highly susceptible to the disease (^{López et al., 2006}; ^{Ramírez, 2008}). The management of this disease is based on the integration of agronomic practices such as modernization, reduction of primary inoculum, planting of highly productive clones and continuing implementation of sanitation practices and cultural management; however, little training to farmers and low income make it difficult to implement control (^{López et al., 2006}). It is therefore necessary to generate alternatives to reduce the losses caused by this pathogen and to improve yields (^{Meza and León, 1972}; ^{Merchan, 1980}; ^{Reyes and Marín, 1981}; ^{Barros, 1982}; ^{González, 1982}; ^{Sánchez, 1982}; ^{Cruz, 1986}; Gamboa and Rincón, 2003; ^{Palencia and Mejía, 2003}; ^{Phillips, 2004}; ^{Phillips, 2006}).

There is a steady increase in demand for organic cocoa increase; however, the supply is insufficient (Tropical Agricultural Research and Higher Education, 2010), therefore, the need to develop alternatives for the control of moniliasis, accepted within the regulations of organic production arises. The use of extracts of plant origin allows obtain the certified organic crops more easily. Another advantage is that production costs are low and with proper management plan are increased the chances of controlling pests and get a good quality product for the market.

The mankind became aware of toxicological, pharmacological and hallucinogenic plants well in advance of their actual discovery by the phytochemical. The natural pesticides have been used in agriculture as an alternative for the management of phytosanitary problems (^{Vergara, 1997}). Various studies show the potential of plant extracts in the management of phytosanitary problems caused by fungi (^{Hernández et al., 2007}; ^{Ramírez, 2008}; ^{Barrera and Bautista, 2008}; as reported by ^{Ramírez et al., 2011}); the same author, reported the inhibitory effect on the growth and development of M. roreri with extracts from Origanum vulgare L. (oregano), Tradescantia spathacea Swartz (purple maguey) and Zingiber officinale Roscoe (ginger). Therefore, this paper presents optimize the process of obtaining extracts, evaluating the solute-solvent ratio in the extraction process by distillation both with fresh material as dry of Origanum vulgare, Tradescantia spathacea and Zingiber officinale on growth inhibition and formation of conidium of M. roreri under laboratory conditions and as an alternative for the management of moniliasis of cacao in organic production systems.

Materials and methods

The research was conducted at the Laboratory of agrotechnologies of the AUDES Cocoa-Chocolate of the UNACH located in University City, Tuxtla Gutiérrez, Chiapas, Mexico.

Results and discussion

The results obtained for oregano extract showed inhibitory effect on the mycelial growth of M. roreri and formation of conidium: total and germinated (Table 2) at concentrations of 50 and 40%. Treatments O1, O2, O3, O5 and O6 showed 100% inhibition for both mycelial growth and for formation of conidium; in this case was 40% CMI. These data confirm the results obtained by ^{Ramírez et al. (2011)} who mentioned that the hydrolate 50% oregano completely inhibits the pathogen.

It is very important to note that to extract the greatest amount of metabolites present in the plant was necessary to use 300 g L^-1 (fresh plant) and the water-alcohol solvent (10:1), because by using dry material metabolites present in the plant apparently degraded. Similarly, ^{Álvarez et al. (2008)} evaluated the influence of the method of drying the leaves of the genus Erythroxylum confusum on the phytochemical composition and variation of metabolites, they recommended using drying in the shade of the plant material as a way to conserve resources and eliminate possible decomposition of metabolites.

The O4, O7 and O8 treatments allowed mycelial growth and conidium formation at all concentrations; however, oregano had an inhibitory effect on seed germination at 50 and 40%; results that are consistent with those reported by ^{Ramírez et al. (2011)} who mentioned that all extracts from oregano inhibited the formation of conidium between 100 and 71% although, as noted above, formation of mycelium appeared, therefore these extracts show antisporulating activity. ^{Cáceres et al. (2013)} determined the inhibitory effect of clove Eugenia cariophyllata, cinnamon Cinnamomum zeylanicum and oregano variety Lippia berlandieri obtained by the technique of hydrodistillation on six major pathogens that attack food (Fusarium oxysporum, Alternaria alternata, Geotrichum candidum, Trichoderma spp., Penicillum digitatum and Aspergillus niger), the authors mention that the aqueous extract of oregano showed higher biological activity against fungi under study.

The comparing means (Tukey p≤ 0.05) showed differences between hydrolats oregano when compared with the chemical and absolute control, which recorded the highest value of sporulation with 951.94 x 10⁵ total conidium mL^-1 and 6.66 x 10⁵ germinated conidium mL^-1, the O1 showed the best results as it did not present conidiums training; besides the hydrolats obtained in this treatment compared to the other treatments used less time distillation, thereby efficiently time and energy required for extraction. According to ^{Carrillo et al. (2010} reported by Kordal et al., 2008) mention that the carvacrol and thymol are compounds of terpene units present in the essential oils of some species of the Lamiaceae family as O. vulgare, T. vulgaris K and M. piperita, of which we found acting causing alterations in morphology and hyphal aggregates, which causes growth and lysis reduce wall and cell membrane of the pathogen occurs.

In the Table 3 shows the antifungal potential of purple maguey extract on mycelial growth and formation of conidium of M. roreri seen. It is appreciated that the M1, M2, M5, M6 and M7 treatments inhibit mycelial growth of the pathogen in 100% at 50 and 40%; so CMI was 40%. The M3 and M4 treatments 50% have total inhibition of the fungus; but at concentrations of 40%, they showed inhibition rates of 52 to 70%. With regard to treatment M8, it inhibited from 48 to 100% mycelial growth of the fungus at five concentrations evaluated. The M1 was the treatment that allowed increased extraction of metabolites, which inhibited mycelial growth. Also presented the shortest time used to obtain the extract (2 h 46 min) compared to extracts made from dried material.

The information generated purple maguey shows that has able to inhibit the growth of disease-causing fungus metabolites because its CMI was 40%; I thereby improving reported by ^{Ramírez et al. (2011)} who mentioned that the purple maguey hydrolats at the 50% completely inhibits the pathogen.

^{Pupo et al. (2010)} mention that the purple maguey has antifungal potential against the causative agent of early blight of tomato (Solanum lycopersicum), as the authors evaluated plant extracts eleven plants, including extracts Cleome gynandra, Tradescantia pallida (Rose) and T. spathacea, did not reach 10% inhibition with any of the doses used in the study. Therefore the data of these authors differ with the results obtained in this investigation.

With regard to the formation of totals and germinated conidium, it shows that there are significant differences (p≤ 0.05) between the treatments applied; that is M1, M2, M4, M5, M6 and M7 treatments show inhibition in the formation of total conidium germinated and at concentrations of 50 and 40%, the lowest value of the CMI (40%).

The treatment M3 to 50% inhibited the formation of conidium, but in 40% concentration 2.69 x 10⁵ total conidium mL^-1; although in this case the conidium failed to form the germ tube. Treatment M8 shows that although formation of conidium was presented in a range of 52.69 x 10⁵ to 180.62 x 10⁵ total conidium mL^-1 in five concentrations tested, fail to germinate, so do not allow the infection occurred pathogen in the fruit and likewise conidium production when compared to the absolute control which registered a value of 591.94 x 10⁵ conidium mL^-1 is reduced, and 6.66 x 10⁵ conidium germinated. Purple maguey leaves used for the production of extracts had a humidity of 91%, these data are consistent with those reported by ^{Reyes et al. (2009)} who expressed the moisture from the fresh leaves of purple maguey is 91.5%.

In Table 4 the effect of ginger extract against the pathogen detailed, J1, J2, J5 and J6 treatments inhibit mycelial growth using the 10:1 ratio, that 50 and 40%, with a percentage of inhibition 100% being the CMI of 40%. It is noted that J3, J4, J7 and J8 treatments have mycelia growth inhibition percentages ranging from 0 to 58% at five concentrations; so the metabolites present in ginger were extracted in smaller quantities because water was used as solvent, added to the plant material was dried in the sun. Apparently J1 treatment that fresh plant material and the ratio (10:1) was used to obtain it was the most efficient in the extraction process, requiring a time in the distillation process 2 h 36 min. The results coincide with those reported by ^{Nguefack et al. (2004)}, who evaluated the inhibitory effect of extracts of Cymbopogon citratus, Monodora myristica, Ocinum gratissimum, Thymus vulgaris and Origanum vulgare against three fungi food Fusarium moniliforme, Aspergillus flavus, Aspergillus fumigatus finding that hydrolats of the five plants present metabolites that inhibit the growth and formation of conidium of the three fungi studied.

Furthermore, J1, J2, J5 and J6 treatment obtained 10:1 inhibited the formation and conidium germination at 50 and 40% and, J3, J4, J7, and J8 relative 10:0 registered 100% inhibition germinated conidium, although allowed the formation of conidium, however they are below the absolute total of conidium witness, whose value was 591.94 x 10⁵ total conidium mL^-1. ^{Ramírez et al. (2011)} state that ginger hydrolats recorded as effectively as its CMI is the lowest 30%. ^{Peña et al. (2004)} show the effect of different plant extracts (garlic, ginger, neem, aloe, etc.) against Thielaviopsis paradoxa of pineapple, which causes black rot of the plant. ^{Sivasothy et al. (2011)} evaluated the essential oils obtained by hydrodistillation oregano leaves and rhizomes of the plant, finding that the oils obtained both leaf and rhizome Zingiber officinale var. Rubrum Theilade, have antibacterial activity against gram positive bacteria Bacillus cheniformis Bacillus spizizenii and Staphylococcus aureus and gram-negative bacteria, Escherichia coli, Klebsiella pneumoniae and Pseudomonas stutzeri.

Conclusions

The hydrolats oregano, ginger purple maguey and at concentrations of 50 and 40% both as fresh plant as a material drying in the sun, have metabolites with ability to inhibit growth and formation of conidium of the fungus M. roreri. Considering that for better extraction of metabolites, the studied plants require alcohol and fresh plant material (300 g L^-1).

For extraction of metabolites of purple maguey that inhibit the growth and development of M. roreri may do so with water as a solvent, since it inhibits solvent like water-alcohol (10:1).

The hydrolats ginger and more effective in inhibiting the growth and development of M. roreri oregano were obtained 300 g L^-1 (fresh), 45 g L^-1 and 90 g L^-1 (dry) with a water solvent -alcohol (10:1).