RESEARCH WORK

Collection of Jatropha curcas and its performance in nursery and establishment stages (Technical note)

Estación Experimental de Pastos y Forrajes "Indio Hatuey".Central España Republicana, CP 44280, Matanzas, Cuba
E-mail: rmachado@indio.atenas.inf.cu

ABSTRACT

The objective of this work was to collect J. curcas material with adequate morphological characteristics for seed production, as well as to determine its performance in the nursery and establishment stages. In nursery variation was observed in the necessary days for the rooting of the propagules (14 to 35 days) and in seedling emergence (7 to 28 days). The propagule survival fluctuated between 73 and 100%; while starting from seed it was between 26,6 and 85,0%. The survival in the field stage varied between 45,4 and 93,3% in the provenances transferred by propagules, but in most it turned out to be lower than the one detected in the nursery. In the provenances directly sown variation was also detected in survival, but the number of plants emerged after 56 days was high. Under these conditions a similar variation pattern was maintained in the percentage of rooted plants and survival, but the effect of the stress caused by the transfer was evident. It is concluded that the age of the plants and the parts selected in the donor material, as well as seed quality, could have influenced the variation of the necessary days for rooting or emergence and the survival percentage. Using the procedure described for the collection of J. curcas is recommended, emphasizing the vegetative way, in order to have access to provenances with adequate characteristics for seed production and with it maintain the genotype of the collected materials.

Key words: Plant collection, Jatropha curcas.

INTRODUCTION

Jatropha curcas is a multipurpose species of the Euphorbiaceae family which has shown potential for biofuel production and other coproducts of relevant importance.

In a review made by Toral et al. (2008), this species was said to be distributed throughout the island of Cuba and the Isle of Youth, although its highest concentration has been determined in the eastern provinces, where it is used as living fences and for the production of artisanal soaps and glycerin.

Jongschaap et al. (2007) stated that J. curcas is a wild species and that the genetic identification of provenances and their performance in different sites and under different conditions should be a priority in research. In this sense, Azurdia et al. (2008) included, as part of the tasks of a study developed in Guatemala, the collection and establishment of the germplasm bank and its agromorphological and molecular characterization; while Mendoza (2009), in a research for the development of J. curcas in Ecuador, presented as a goal of the project the creation of characterized and evaluated banks, the attainment of promising cultivars and the establishment of demonstrative lots. Martínez et al. (2007) considered important to perform the search for more collection sites for this species and Sujatha et al. (2008) stated, as limitations for the effective use of J. curcas: the lack of knowledge about genetic bases, poor yields and low existing genetic diversity.

For all these reasons, the collection and introduction of the highest possible quantity of provenances of this valuable species is considered important, which would allow creating germplasm banks in different sites where the material is circumstantially increased and conveniently characterized, at least from the morphological and agronomic point of view, in a first stage, so that the necessary basis is made for the identification and casuistic selection of outstanding types for their future multiplication and use.

The objective of this work was aimed at collecting J. curcas materials with adequate morphological characteristics for seed production in certain zones of the Sancti Spiritus province, as well as determining their performance in the nursery stage and during the establishment of the germplasm bank.

MATERIALS AND METHODS

Collection zone and procedure. Two collection missions were carried out in certain zones of the central and south Sancti Spiritus province: in the first one preference was given to obtaining seeds; while in the second one the collection of vegetative material (propagules) received priority. In both cases the collection zones were characterized by a higher presence of Brown soils (Hernández et al., 1999). For the collection in the donor plants some requisites were considered which, on the one hand, limited the speed of the process; but on the other hand, allowed the selection of donor plants with adequate morphological characteristics for seed production. Thus, preference was given to seed or propagule (cutting) collection from preferably isolated, well ramified, vigorous individuals with abundant leaves per bud, and little or no affectation by pests or diseases. Nevertheless, material from individuals that were part of wild populations, in higher or lower abundance, and others that were in the limiting fences of paddocks and other crops, was also collected, but with the condition that no effect of previous successive pruning was observed in them.

The propagules were obtained by cutting the branches with a higher or lower caducity degree, but always discarding the apical portions, in which the tissue was still marrowish and the buds were immature and little developed. Thus, 15 or more cuttings were cut in each of the donor plants, around 30 to 40 cm long and one to four cm of diameter approximately.

The pruned cuttings were bound together and conveniently identified and wrapped with paper, which was maintained moist until arriving at their destiny.

A provenance collected in Matanzas province was added to the seed collected in Sancti Spiritus.

All the germplasm was transferred to the Experimental Station of Pastures and Forages «Indio Hatuey» and to the Experimental Station of Pastures and Forages of Sancti Spiritus, in order to be put in nursery and later planted in the area destined to the creation of the germplasm bank.

Nursery stage. The cutting planting and seeding in the nursery were performed on March 16th, 2009. For that purpose, 20 x 12 cm nylon bags were used. The substratum used consisted in a mixture of soil (70%) and organic matter (30%).

The provenances collected and planted from seed were: SSCS-4, wild population, SSCS-3, SCS-1, SSCS-6 and San Miguel. Two provenances given by the Institute of Forestry Research (D-1 and D-2) were also planted.

The provenances obtained from propagules were SSCE-7, SSCE-8, SSCE-9 and SSCE-10, as well as Cabo Verde, Las Tunas and Sancti Spiritus, which donors were in experimental areas where they had been previously evaluated (Machado and Suárez, 2009).

The lack of survival of the materials planted in nursery, from seed, motivated the creation of a new nursery, which was created under shade conditions on May 19th, 2009. From this nursery no seedlings were used for their transfer to field conditions, because they were only 28 days old when the germplasm bank was created, for which seed was used for planting it, except in the case of the provenance SSCS-6, from which no seed reserve was left.

Establishment stage. The germplasm bank was seeded or planted on June 18th, 2009. For that purpose the provenances were placed in niches spaced at 2,0 m between rows and 2,0 m between plants, for a total of 10 niches, so that 8,0 x 2,0 m plots were formed separated by 3,0 m on both sides.

In the next six months (period that was considered as establishment stage) the corresponding agronomic labors were maintained, which consisted in manual weeding of the plots and the spaces between plots, as well as plant thinning (when there were more than ten). During that period observations were made on the number of rooted and emerged plants, from which the survival percentage (before thinning) was calculated, based on the total number of planted propagules or sown seeds, respectively.

RESULTS AND DISCUSSION

Table 1 shows the location and environment where the collections were made, as well as the status of the plants, type of prevailing vegetation, land use and specific habitat.

As it is observed, the number of collected accessions was not high. This was caused, mainly, by the short time period dedicated to the two collection activities, the search for and preference given to the plants that showed adequate morphological characteristics and the fact that this species is not abundantly distributed in wild habitats; while in the populations that were part of living fences and hedges, the individuals to be selected were scarce because in many cases the plants were pruned.

The collection was made in plants that remained in wild or cultivated state. However, in this last case the precaution was taken that the chosen individuals did not have the effect of successive prunings, so that the number of branches present obeyed a natural morphological pattern and it was not expression of the branching produced when plants are subject to successive foliage cuttings (Dias et al., 2009).

The assumed requisites in the collections of these materials allowed choosing adequate phenotypes for seed production, which were different or very different, in each case, in correspondence with their specific genotypes.

For such reason, it is presumed that these provenances in the germplasm bank are manifested with a more or less important diversity degree, from the morphological as well as the phenological expression point of view.

During the nursery stage a remarkable variation was observed in the necessary days for the sprouting or seedling emergence (table 2). This performance could be related to the age of donor plants, their individual characteristics and to the plant parts from where the propagules were chosen. In the provenances collected this way (from SSCE-6, previously collected by seed, to SSCE-10), the donor individuals were tall, thick and vigorous (old) trees, which cuttings were indistinctly selected in more or less young branches. In these provenances the presence of sprouts began to be observed 35 days after their planting in the bags, time they needed to activate their dormant buds.

However, in the provenances Cabo Verde, Las Tunas and Sancti Spiritus the sprouts began to be clearly observed after 14 days. In this case, the donor plants were two years old and the propagules were chosen from young branches, in which the buds were turgid and very vigorous, aspects that can justify such performance and warn about the importance of taking them into consideration in future collection missions, due to the possible effects which can be exerted on survival.

Regarding the survival percentage, it is valid to state that it fluctuated between 73 and 100%, except in the provenance SSCE-6, which propagules did not show sprouting. This high survival percentage contributed to the fact that the number of propagules ready to be developed as plants in the germplasm bank exceeded, in this stage, the number of necessary plants for its creation, and particularly in the provenances in which propagules of younger branches and plants were used.

Seedling emergence in the nursery stage (seeding) started after seven days for most provenances planted this way, except for D-2, which started after 14 days, but with the inconvenience that the seedlings began to die rapidly between 21 and 28 days, and only eight seedlings were left at the end.

Although the seedling number was enough for the creation of the germplasm bank, their age (28 days) did not allow them to reach the adequate height for transfer to the field (35-45 cm) and they were seeded, except SSCE-6, from which there was no reserve and was transferred under those conditions (plantlets).

Table 3 shows the number of rooted plants, emergence and survival percentage in the field stage, since seven days after planting or seeding, until 56 days. In these results a noticeable variation for this last indicator was also detected, with values that oscillated from 45,4% to 93,3%.

Nevertheless, it should be noticed that the survival percentage in the field stage for the planted material was lower, or sometimes much lower, than the one detected under nursery conditions (table 2), possibly due to the stress suffered by the plants transferred from the nursery or sown directly. The highest values were only detected in the case of the provenances SSCE-10 and Las Tunas, of which 10 and 14 from the 11 and 15 propagules transferred to the field, respectively, survived, with which they reached 90,9 and 93,3% in this indicator; as well as in SSCE-6, with 91,6% survival in spite of being very little developed plantlets.

Thus, the high survival percentage of SSCE-6 under field conditions was also higher than the one reached under nursery conditions (85%). This could be related to the nature of the propagation material, because this was the only provenance transferred to the field from its seedlings (plantlets) originated from seeds, which develop the root system characteristic of J. curcas, constituted by a main root and four very strong branches or primary roots of fast and efficient anchorage to the soil, with which a high percentage of living plants is achieved (Sunil et al., 2008).

For the case of the provenances directly sown in the field the variation in terms of survival was also remarkable, but in all cases the total number of plants rooted after 56 days was considerably high and for such reason a thinning labor was performed leaving the most vigorous plants.

In correspondence with the results it is concluded that the age and plant parts chosen in the donor material, as well as the seed quality, could have influenced remarkably the variation found in the necessary days for rooting or emergence, as well as the survival percentage of the provenances used under nursery conditions. When the propagules were transferred to field conditions a similar variation pattern was maintained, in the rooted plants and survival percentage, where, with rare exceptions, the effect of the stress caused by the transfer to the new condition was evident.

Carrying out the collection of J. curcas is recommended, through the vegetative way, in order to have access to provenances with adequate characteristics for seed production, and thus maintain the genotype of collected materials and select propagules of branches with turgid and vigorous buds that allow a high survival percentage.