Researchers manage to produce baru seedlings through grafting

Technique guarantees the multiplication of plant species while maintaining their characteristics, favoring greater productive potential

03.07.2023 | 17:23 (UTC -3)
Juliana Miura
Photo: Wanderlei Lima
Photo: Wanderlei Lima

Grafting, a vegetative propagation technique for the production of clones, proved to be viable for the multiplication of baruzeiro. Recent work carried out at the Embrapa Cerrados nursery, in Planaltina (DF), has shown promising results for three types of grafting – plate grafting, simple English grafting and full cleft grafting (see table at the end of the article). For seedlings grown in full sun, the three types provided average set rates above 50%, with emphasis on bubbly, which achieved set rates of more than 60%.

Vegetative or clonal propagation consists of multiplying parts of the plant of interest without using seeds, giving rise to others identical to the mother plant (clones). The main advantages of the method are the possibility of forming high-productivity, highly uniform clonal plantations and, sometimes, bringing forward the reproductive phase of the species.

In addition to grafting, other methods of asexual reproduction or vegetative propagation are cuttings, minicuttings and micropropagation.

These are the first results for the development of a production system for baruzeiro. “We emphasize that we are working with a native tree species, lacking technical information on this subject and we believe that this data will serve as a basis for new studies with the aim of refining the grafting methodology for the species”, emphasizes researcher Wanderlei Lima, coordinator of the study .

The complete results are in the article “Evaluation of grafting methods on baruzeiro seedlings (Dipteryx alata Vogel, Fabaceae)”, published in the magazine Ciência Florestal, April/June 2023 edition. Lima explains that the next step is to improve the process, using the experience acquired in the first experiment to increase the grafting percentage.

The result was very positive, in the opinion of the team, also composed of analyst Fernanda Morais and assistant Vicente Moreira. Some seedlings grafted at Embrapa Cerrados have already been transplanted into the field on the border of the Crop-Livestock-Forest Integration experiment, in which the use of native Cerrado species in this system is being evaluated (read article). One of the main challenges for domesticating the baruzeiro is precisely the production of seedlings. Currently, there is no validated asexual reproduction methodology for this species.

Photo: Wanderlei Lima
Photo: Wanderlei Lima

The baruzeiro (Dipteryx alata Vogel)

Also known as cumbaru or cumaru, the baruzeiro is a tree between 15 and 25 meters tall and widely distributed in the Cerrado. This is one of the biome's native species with great economic potential due to its diversity of uses. The fruit pulp can be consumed fresh or in mixtures and the endocarp can be transformed into high-calorie charcoal. The seed is the best known part and has gained market value, being used in national and international cuisine. It resembles a chestnut and is enjoyed as an appetizer and used in various recipes. The oil extracted from the seed also has varied uses. The tree can be used in landscaping and its wood has great strength and durability.

The baruzeiro is one of the most promising Cerrado species for cultivation. The generation of information about its multiplication, growth, development, productivity and variability will allow its domestication for the implementation of commercial crops. Currently, practically all production comes from extractivism.

The experiment

Three types of grafting were tested (plate grafting, simple English grafting and full split grafting) in three rootstock seedling training systems (in plastic bags in full sun and under shade and in tubes in a suspended nursery in full sun). The seedlings (rootstocks) were formed from seeds collected from adult baruzeiro plants from the Embrapa Cerrados Experimental Field. The buds used for the grafts were obtained from adult Embrapa trees.

The performance of the plants was different according to the driving system. “We consider the system of producing seedlings in plastic bags in full sun to be the best, with which we achieved more than 50% success rate in the three types of grafting that we used in our study, with emphasis on grafting, followed by simple English grafting and grafting. full slot forking”, informs Lima.

According to the researcher, only full cleft forking showed a set rate greater than 50% for seedlings grown under shade, indicating that it is a technique for reproducing the species in this condition. However, the time needed for the seedlings to reach the ideal diameter for grafting was longer in systems under shade. Considering that the seedlings were formed on the same day, the seedlings grafted under shade only reached the ideal diameter three months after the seedlings grafted in full sun.

This is important information for the multiplication and domestication of the crop, since the longer it takes for the seedling to reach the ideal diameter for grafting, the greater the costs at this stage. Regarding the third training system, Lima explains: “In this study, we chose not to graft seedlings grown in tubes, in a suspended nursery, as these showed the worst growth and development performance”.

The researcher considers this a very positive result: “Being a first experiment, the values ​​were very satisfactory. Our goal is to reach 80% by refining the technique and checking some factors that may have interfered with the development of the seedlings.” Lima highlights that the experiment was carried out during the most critical period of the Covid-19 pandemic, when several works were compromised.

Based on the results of this experiment, a research recommendation for those interested in producing baruzeiro seedlings is to redo the grafts that did not take root. “This guarantees the reduction of production costs, as it reuses the seedlings from the rootstocks”, he explains.

promising results

Vegetative propagation or cloning has proven to be an excellent tool for forestry production in Brazil, providing increased productivity in forests planted with non-native species. But its use in native tree species is still incipient.

The few existing baruzeiro orchards are formed by seedlings made from seeds. “Sexual reproduction [using seeds] involves great genetic variability and therefore does not guarantee that the children will have the same characteristics as the mother. Asexual reproduction [vegetative propagation], with the production of clones, guarantees that these characteristics will be maintained. This is an important tool for multiplying materials of different interest”, explains Lima.

Previous work, carried out in 2002 and 2003 at Embrapa Cerrados, evaluated other methods of vegetative reproduction for the baruzeiro. Cutting, despite being a widely used technique for forest species, did not produce good results, as the tree is difficult to root. The buds sprouted, but no roots emitted. In parallel with the current grafting experiment, epicornal shoots were stimulated through drastic pruning of adult plants, so that new shoots would emerge. According to the researcher's assessment, the species resprouts easily and the use of these sprouts represents a potential source for asexual reproduction that has not yet been explored.

Grafting serves two functions: it helps the genetic improvement of the species and enables the multiplication of superior plants. “Grafting can be the first step towards the domestication of species native to the biome, especially those that are difficult to reproduce by cuttings. This way, it will be possible to select elite materials with desirable characteristics, such as smaller plant size to facilitate management, for example, to guarantee the formation of more homogeneous orchards with greater production potential”, informs the researcher. Another advantage of using the technique is the shorter timeframe for starting production.

The scientist reports that, in recent decades, the demand for products obtained from native Cerrado species has consistently increased. Despite this scenario, much of the production is still obtained through extractivism. Baru stands out among the native fruit trees with the greatest economic potential, with demand for the recovery of degraded areas, restoration of legal reserves and the formation of commercial orchards. “Its domestication can open up a very profitable market for producers in the region”, he concludes.

How is grafting done?

A large proportion of fruit trees are produced by grafting. In addition to maintaining the desirable characteristics of the resulting plant, it is a quick and reliable means of reproducing superior plants for commercial cultivation.

The operation involves the introduction of a bud, shoot or branch of one plant, called a graft or horse, into another, known as a rootstock or horse. The grafted plant (horseman) carries the characteristics that you want to obtain in the new plant and is the one that will produce the fruits. The horse takes the root system and part of the stem. It is responsible for supplying water and nutrients to the plant and ensuring its adaptation to soil and climate conditions.

Types of grafting evaluated in the experiment

In grafting, a branch of a plant whose characteristics are desired to be maintained is “implanted” into the stem of another plant, fusing these two parts.

• Bubble – A vegetative bud (bubble) is detached from the plant you want to multiply and introduced into a cut made in the seedling that will serve as a rootstock.

• Forking – Parts of two plants with the same diameter fit together perfectly. A rope is tied to ensure the union of the fragments.

Full slot and simple English forks differ in the type of cut that is made in the parts of the plants for fitting. The first is made with a V-slot and the second with a transverse cut.

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