RESEARCH WORK
Morphological and agroproductive characterization of Ricinus communis L. provenances for oil production
R. Machado1, J. Suárez1 y Marlen Alfonso2
1 Estación Experimental de Pastos y Forrajes «Indio Hatuey». Central España Republicana CP 44280, Matanzas, Cuba
2 Instituto Cubano de Investigaciones de Derivados de la Caña de Azúcar (ICIDCA), La Habana
E-mail: rmachado@indio.atenas.inf.cu
ABSTRACT
The objective of this work was to characterize two provenances introduced from South America (Planta-2 and Planta-3) and three provenances collected in Cuba (SSCS-5, Colón-1 and Las Tunas), of Ricinus communis L. For such purpose, morphological and agroproductive indicators were considered. Plots measuring 40 m2 (vital area) were used, with ten plants. The design was completely randomized and the data were analyzed from descriptive stadigraphs. Planta-2 reached the highest growth rate (2,98 cm/day) and, at 17 months of age, it was superior regarding: stem diameter (17,5 cm); number of primary (45), secondary (41) and tertiary branches (20); and the diameter of primary branches (5,9 cm). SSCS-5, Colón-1 and Las Tunas showed longer racemes, with a higher number of fruits; but they were surpassed by Planta-3 and Planta-2 in fruit weight per raceme (134,9 and 139,0 g, respectively), with larger fruits and seeds. The lesions caused by insects and the degree of infestation by pathogen microorganisms were not representative. The highest seed yield (95,1 kg), fruit yield per plant (5,28 kg) and per area (4 398 kg/ha) and the estimated oil yield per area unit (1 130,2 kg/ha) were detected in Planta-2. These provenances were concluded to have morpho-productive characteristics that differentiate them from each other, and to show relevant particularities for oil production, which is destined not only for biodiesel production, but also for many uses from its derivatives. To conduct further studies on the management of R. communis, particularly in Planta-2, as well as to introduce medium-sized types that facilitate their harvest, is recommended.
Key words: castor oil, provenance, Ricinus communis L.
INTRODUCTION
Castor oil plant (Ricinus communis L.), C3 plant from the Euphorbiaceae family, is a monotypic species constituted by 22 subspecies, as well as by a remarkable number of cultivars created by plant breeders for their utilization (Webster, 1994). At present, it is considered one of the most important species of the plant kingdom. Flemming and Jongh (2011) stated that from its different components, particularly seeds, 700 industrial products drugs, cosmetics, lubricants and varnishes- may be obtained, and that currently its use as ecological fuel (biodiesel), which is less environment-damaging, has begun to be studied (Gama da Silva and Guimaraes Filho, 2006). Of this oil between 350 and 700 kg/ha may be produced with minimum crop management, and up to 1 250 kg/ha in more technological cropping (Mazani, 2007); although the seeding date and genotype significantly influence this indicator (Verissimo et al., 2009).
Beltrao, Cardoso and Severino (2005) state that the castor oil plant has tropical origin and is from northern Africa, specifically from Ethiopia, where it has been known for more than 6 000 years. It is adapted to arid, semiarid and impoverished zones; but its drought-resistance is one of its most outstanding characteristics (Pereira de Oliveira et al., 2005). Although it is a demanding crop (Soares et al., 2006), it prospers well on moderate-fertility, deep, permeable, aerated, well-drained soils, with adequate amounts of nutritional elements and pH above 5,5.
In Cuba, where it has been naturalized, it may be found practically throughout the country, forming wild, more or less widespread populations. It is very common to observe this plant in uncultivated soils, paddocks and crop lands, but especially in sites where debris and wastes are accumulated. However, the differentiation and the agronomic potential of the naturalized and introduced species for being used in the production of energy and other products, from its seed oil, are unknown. Hence, the objective of this work was to characterize introduced and collected castor oil plant materials, based on morphological and agroproductive indicators, for oil production.
MATERIALS AND METHODS
Characterized material. Five R. communis provenances were characterized. Three of them were collected in Cuba: SSCS-5 (Sancti Spiritus province), Colón-1 (Matanzas province) and Las Tunas (Las Tunas province); while the other two provenances were introduced from South America through a donation. They were named Planta-2 and Planta-3.
Seeding. Seeding was carried out on June 18, 2009. The seeds were placed in holes spaced at 2,0 m between rows and 2,0 m between plants. Ten holes were planted, so that they formed plots of 40 m2 of vital area. The plots were separated by a distance of 3,0 m in both directions. During the establishment observations were made of the number of emerged plants (in the first 56 days) and their height (in the first four months), from which the survival percentage and growth rate (cm/day), respectively, were calculated.
Characterization. For the characterization the following descriptors were considered: plant height (cm); stem diameter at the basis (cm); number of primary, secondary and tertiary branches; and diameter of primary branches (cm). The six indicators were measured or counted at two moments: four and 17 months after seeding regarding the growth rate, and in the final stage of the biological cycle of the plants. The raceme length (cm), number of fruits per raceme, average weight of the fruits of a raceme (g), total number of harvested fruits, total fruit yield (kg), fruit yield per plant (kg), harvest number, presence and lesions caused by phytophagous insects (%), infestation caused by pathogen microorganisms (%), plant persistence (%), weight of 100 seeds (g), number of seeds in one kilogram and seed dimensions (cm); as well seed yield per plant (kg) seed yield estimate per area unit (kg/ha), were also considered. To calculate this last indicator, a plant density of 833 plants/ha was assumed, based on the size reached by the plants.
Indicators related to the physical characteristics of the fruits (husk and seed percentage) and to the oil content in the sample (g), oil percentage in the seed and estimated oil production (kg/ha), were also determined.
Design and data analysis. A completely randomized design with ten repetitions was used; the experimental units were the plants. For interpreting the results the description of the measured, estimated and counted indicators during the experimental period was used, based on the descriptive stadigraphs (average). For such purpose, the statistical pack SPSS version 11.5 was used.
RESULTS AND DISCUSSION
Table 1 indicates the results of emergence and survival percentage in the field stage, since seven until 56 days after seeding. SSCS-5 reached the highest emergence 56 days after seeding; while Colón-1 and Planta-3 did it 28 days after planting, and Planta-2 and Las Tunas after seven days. In general, the emergence percentage is within the range indicated in literature, because in some accessions germination and emergence percentages have been found from 0 to 100%, but they have been high in most cases (Miranda, 2011). The values found, according to the indications by this author, may have been due to the low germination capacity of certain provenances, associated to the genetic material or the species, which shows ecotypes with low reserve contents aspect which is determinant to reach an adequate germination percentage-, in addition to the seed's age.
Flemming and Jongh (2011) indicated that the emergence of castor oil plant seeds should usually occur between 10 and 21 days after seeding, which was achieved early in all the evaluated provenances. The most remarkable survival values were detected in Planta-2 and Planta-3, which will be discussed later.
Table 2 shows the values of some morphological indicators, at four and 17 months of age. At four months, Planta-2 and Planta-3 were higher than the other provenances regarding height, stem diameter and number of primary branches; while in the number of secondary branches and the diameter of primary branches, SSCS-5 and Planta-2 showed higher values.
Nevertheless, it is important to emphasize that 17 months after seeding Planta-2 and Planta-3 also surpassed the other collected provenances in terms of height. However, only Planta-2 surpassed all the materials in terms of stem diameter, as well as in the number of primary, secondary and tertiary branches at that age. In the diameter of primary branches it was surpassed by SSCS-5 and it was similar to Colón-1, with which it revealed a remarkably favorable and highly vigorous morphological conformation.
The lowest number of primary branches at 17 months of age was detected in SSCS-5; but this accession and the others surpassed Planta-3 regarding the number of secondary and tertiary branches, and diameter of primary branches.
It was interesting to verify that the height of Planta-2 at four months of age was similar to the one reached 17 months after planting. This indicates that it had vigorous growth and reached the maximum height in only 120 days, which is explained by the high growth rate of this accession, particularly in the third month with more than 7 cm/day-, stage in which all the provenances developed the highest growth rate (table 3).
Independently from the detected values, it was most interesting to verify that all the provenances behaved as types called «high», because they were capable of reaching more than 3 meters of height. This aspect has been corroborated in the species, which is capable of reaching between one and more than 7 m of height during its life cycle (Mazzani, 2007; Miranda, 2011).
The provenances SSCS-5, Las Tunas and Colón-1 showed longer racemes and with a higher number of fruits, particularly SSCS-5. Nevertheless, they were surpassed by Planta-3 and Planta-2 in average fruit weight per raceme, because they showed larger fruits, which contained larger seeds, and occupied a higher percentage (table 4).
Raceme length, number of fruits per raceme and fruit weight per raceme, are very variable characteristics in R. communis. Rico-Ponce (2011), when evaluating 16 genotypes in fourteen states of Mexico, reported lengths which fluctuated between 18,7 and 36,6 cm in the first raceme and an average fruit weight per raceme of 68,7 g, in plantations with a density of 2 500 plants/ha. In this last characteristic all the evaluated provenances showed representative values, higher in Planta-2 and Planta-3; but the husk percentage was within the range reported by this author (34,0-52,6%).
As it is observed in table 5, the highest number of harvested fruits until October, 2010, corresponded to SSCS-5 followed by Las Tunas and Planta-2. Nevertheless, the highest total fruit yield and fruit yield per plant were detected in Planta-2. The provenance Planta-3 surpassed Colón-1 only in terms of total fruit yield, but it yielded four times less and its productivity per plant was three times lower as compared with Planta-2.
On the other hand, the individuals of Planta-3 were partially or completely deteriorated until reaching total necrosis and concluded with 14% persistence, for which they only allowed 14 harvests in correspondence with their productive cycle, practically behaving as an annual type.
The other provenances, particularly Planta-2 with 95% persistence (living plants) and Colón-1 with 87%, remained in full production and, according to the field observations, were kept vigorous and with high generation of racemes and fruits almost until the end of the second year, for which they practically behaved as biennial types.
In all the R.communis provenances the leaf lesions caused by phytophagous insects (mainly lepidopterans and dipterans) and the degree of infestation caused by pathogen microorganisms (presumably from the Cercospora genus) remained with non-representative values. Flemming and Jonhg (2011) referred that a high number of insects and pathogen microorganisms may attack this species, but they usually do not cause important economic damage. Among them, they reported more than 50 different fungi, parasites, nematodes and several insects. Durán et al. (2008) also made reference to diseases caused by Fusarium (F. oxysporum and F. ricini), the rot caused by Botryodiplodia (B. theobromae) and the spots caused by Alternaria (A. ricino) and Cercospora (C. ricinella).
The weight of 100 seeds varied between 13,8 and 81,5 g, and it was higher in Planta-3 and Planta-2 with regards to the others, which was in correspondence with the higher dimension of their seeds (table 6); hence the higher survival detected in these two treatments, which may be associated to a higher reserve content. This variation range coincides with that reported by Mazzani (2007), who indicated fluctuations between 19 and 95 g, and by Goytía-Jiménez et al. (2011), who found that it was one of the variables with higher difference, recording weights from 7,0 to 123,6 g, when they characterized 151 accessions collected in the Chiapas state, México.
Regarding the number of fruits produced, seed yield per plant and estimated yield per area were higher in Planta-2. The lowest values were found in Colón-1, preceded by Las Tunas and Planta-3, which were surpassed in turn by SSCS-5 (table 6). In Brazil, Soares et al. (2006) found yields of 1 072 kg of seed/ha when using the cv. BRS Nordestina, without fertilization, on slightly acid soils (pH 5,6) and with slow values of P and OM. Thus, the estimated yields may be considered relevant in the case of provenances SSCS-5, Las Tunas, Planta-3 and, particularly, Planta-2, in which they were higher. This was related to the fact that the last one produced a higher number of harvests, and also had higher productivity per plant and a longest life cycle regarding its persistence in the field.
However, it is necessary to specify that the excessive growth of the characterized germplasm, especially in Planta-2 and Planta-3, caused difficulties for manual harvest, because the height and space occupied by excessively large and vigorous plants hindered crop management and seed collection, aspect which was indicated by Rodríguez and Duche (2010). This is considered a common condition for most medium-sized to high castor oil plants (Azevedo, 2001), and although commercial varieties reach between 0,90 and 3,0 m (Flemming and Jongh, 2011) many farmers prefer dwarf varieties which grow to an average height of 1,6 m, with periods from seeding to harvesting of 120-130 days; as well as the medium-sized varieties, which grow from 2,0 to 2,5 m, with periods from planting to harvest of 150-240 days (Rodríguez and Duche, 2010), aspect which should be considered.
The oil content of the analyzed samples, oil percentage in the seed and estimated oil production per area unit, regarding seed yield, are indicated in table 7.
Although the seeds from Planta-2 contained a lower seed percentage, this treatment reached the highest oil yield per area unit. A contrasting performance was observed in Planta-3, because it showed the highest oil content in the seeds as compared with the other provenances, but it only surpassed Colón-1 regarding oil production. Yet, in correspondence with the persistence of this last one (table 5), its production could finally be expected to be higher, because it showed a persistence very similar to Planta-2; while Planta-3 concluded its productive cycle much earlier.
The studied provenances of the species R. communis were concluded to have morpho-productive characteristics which differentiate them from each other, and in turn they showed the existence of relevant particularities for oil production related to seed content, production per plant and estimated yield per area unit. For such reasons it is considered, with a biorefinery approach, that R. communis represents a good choice in terms of oil production, which can be used for producing biodiesel, as well as other derivatives, such as: biolubricants, biopesticides, plastics, lacquers, paints, varnishes, cosmetics and many products for medical use.
To conduct further studies on the management of R. communis and its best way of utilization, particularly in the provenance Planta-2, as well as to introduce medium-sized improved types that, with similar or better performance, facilitate their harvest, is recommended.
