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Gabriel Dehon Sampaio Rezende e Bruno Marco de Lima

Bracell Corporate Head of Forestry Research and Development and Bracell Senior Manager of Research and Forestry Development


Clonal compounds of eucalipto

We are often asked if the productivity gains with the genetic improvement of eucalyptus have stagnated. Our answer has been negative, because we believe that in recent years the environment has changed a lot, especially due to the frequent and lasting changes in water regimes, which have reduced the productive potential of traditionally suitable areas. In addition, there was expansion of the forest frontier to less suitable areas, previously unexplored, and also the co-evolution and introduction of new and important pests and diseases.

All this meant that most of the eucalyptus clones selected in previous decades lost adaptation to current environmental conditions, that is, they lost productive potential. But that doesn't mean that genetic gains have stagnated. On the contrary, this challenging scenario allows the gigantic genetic variability available in the genus to be exploited through well-structured and efficient breeding programs, enabling the achievement of new genetic gains. Incidentally, if this is not done, we will certainly witness continued declines in productivity in the future.

But it cannot be denied that the new challenges cited overlapped with the achievement of more expressive gains. Many times these problems resulted in significant losses of investment in the formation of forests. In this scenario, over the last decade we have challenged ourselves to find alternative solutions that at the same time maximize gains and minimize the genetic vulnerability associated with monoclonal plantations. A natural option would be to return to the use of improved seeds to the detriment of clones, as they guarantee greater genetic variability at the plot level and, consequently, lower risk.

However, seeds, no matter how good they are, never capitalize, in the selection process, all kinds of genetic effects, additive and non-additive (dominance and epistasis ), as happens with clones. Another option would be to use a mixture of clones in the same field, but how would it be possible to do that without losing planting uniformity (and consequently productivity), since the mixture would be made with clones originally selected for the formation of monoclonal plantings?

After maturing the theme with Professor Magno Ramalho, from the Federal University of Lavras, a possible solution emerged, consolidated when we watched a basketball game of the National Basketball Association of North America. The players on a professional basketball team of the National Basketball Association of North America are not clones, that is, they have different genotypes.

However, they all have similar phenotypes, in height, weight and speed. And it is this similarity, placed in the form of joint action, that makes a team truly competitive. By analogy, we asked ourselves if it would be possible to form a mixture of distinct genotypes (clones), phenotypically similar, both in growth rate and in wood quality, capable of producing very well when placed to work as a group. But how would it be possible to identify these “basketball players”?

At Fibria , the team responsible for the genetic improvement program began research in this direction. The first step was the definition of an experimental design capable of robustly capturing the differences in behavior of the same clone when competing with itself and with others, in a format that we call “auto” and “allo-competition” . This design was used to establish an experimental network of high quality and very representative in geographic coverage, which could accurately identify and explore the interaction of genotypes with environments (Genotypes versus Environment), both in “auto” and in “allo- competition".

At the same time, we started pilot plantings with mixtures of consolidated commercial clones, in order to anticipate a little of the learning that was to come. In this incipient stage of knowledge, we found that, as the literature anticipated, some clones did not perform well in mixtures, often becoming dominated.

We therefore anxiously waited for the self and allo-competition trials to complete three years for data collection and analysis. The results were astounding. Our original idea was that we could increase the genetic variability at the stand level, without this would imply loss of productivity, but the data showed significant gains in productivity when comparing the 5 or 10 best clones in allo-competition with the 5 or 10 best in self-competition. On that occasion, it became evident that, regardless of the physiological mechanisms that could justify the results, different clones, in different environments, behave differently when competing with themselves (monoclonal plantations) or with a range of genetically distinct neighbors.

Based on this finding, a new approach was created, called Clonal Compounds. It was no longer a question of mixing clones, but of mixing the right clones, that is, those with the best performance in allo-competition, enabling equally uniform plantings to monoclonal ones, but with greater genetic diversity. In 2019, an article containing the results of this work was published in one of the main international scientific journals in the forestry environment, Ecologia e Manejo Florestal (Clonal composites: an alternative to improve the sustainability of production in eucalyptus forests).

Given the positive expectation, the next step was to make the technology operational, both in the nursery and in the field. The first important aspect was the definition of the ideal number of clones for the formation of a Clonal Compound. Although there is no absolute rule, we believe that a good Compost should be formed by the 5 to 10 best allo-competitors of the evaluated population, because in this way a good balance is achieved between maximizing gains and minimizing genetic risks. Another relevant point is the seedling production method in the nurseries, in order to guarantee an effective and homogeneous mixture of the clones of each Compound.

We tested several models and found that the best involves mixing the clones from the mini clonal garden. All Compost clones must be planted in the same channel , in “little blocks” of approximately 100 strains. Although these blocks are formed by each clone individually, the collection of cuttings must be done without distinction, mixing all the clones involved, from staking to expedition to the field, without major complications for the operational activity. In this way, there will obviously be differences in the final use of seedlings from each clone, and consequently the proportion of each one in the expedition batches will not be exactly the same. However, clones that, via this process of natural selection for performance in the nursery, are eventually misrepresented in the field, can be easily eliminated from the Compost, by eliminating their respective blocks of strains in the mini clonal gardens.

But every change brings resistance. Every new paradigm requires effort to break the previous one. As expected, the operational areas initially resisted the new idea.

From the supposedly greater difficulty in producing seedlings to the expectation of greater unevenness in the field, many questions were raised. It was important to remain firm at that moment, confident in the results observed experimentally.

Gradually, we increased the scale of planting and reached more than 30,000 hectares planted at Fibria . After some time, we analyzed the results of the qualitative inventory, and we verified that the uniformity of commercial plantations with Clonal Compounds was fully compatible with that of monoclo nal plantations, being a little less than 6 months, but many times superior to 12 months.

However, after 2 years of age, yields began to draw attention, as they were invariably higher than those of monoclonal plantations. In addition, more than once we saw monoclonal plantations being reformed in advance due to phytosanitary problems, while neighboring plantations with Composts remained productive. The concept was proven in practice. At Bracell , we are implementing the same technology.

In 2020, we began establishing a broad experimental network in the company's different areas of activity. In 2023, we begin to analyze the first results and, in 2024, we will recommend Bracell's first Clonal Compounds for planting on a commercial scale . We have a very positive expectation, since the preliminary results already point to a superior performance of the Clonal Compounds in relation to the best clones individually.

In conclusion, the greatest challenge for eucalyptus breeders is to select clones based on past data, with expectations of future performance. In a scenario where future environmental conditions are increasingly uncertain, we need tools that minimize this risk. We need some kind of “life insurance”. In this context, Clonal Compounds, developed within the aforementioned technical concepts, represent a safe path towards the sustainable supply of wood. Time will prove whether we are right or wrong, but let's not wait and see. We are planting our future now.