For more than 10 years, the period of the so-called megadrought that affects the central-southern regions of Chile has been extended. In that same period, the blueberry market underwent a radical change with the expansion of crops don't chill, the boom in Peruvian production and the increase in varietal supply that, due to commercial competition, is periodically launching new varieties with better, different or new quality qualities. 

It is in this scenario that Cristián Balbontín carried out an investigation of the use of hormonal inducers; abscisic acid (ABA) and methyl jasmonate (MeJA) in cherries, to evaluate their effect on their splitting caused by rains that, erratically, can occur during the ripening and harvest period. The use of these inducers increased the expression of genes related to wax synthesis, as well as the presence of long-chain alkanes, which are the ones that provide greater impermeability to the cuticle.

Along with this, an improvement in fruit quality was also observed, in terms of firmness, soluble solids and color. 

Both cherries and blueberries have similar fruit ripening mechanisms, in terms of the phytohormones involved in this process, which are precisely ABA and MeJA. These hormones are associated with a series of physiological processes in plants, including adaptation to stress conditions (salts, lack of water, radiation). Considering the similarities between both species and the role of these hormones, the engineer and PhD set out to test his formula in blueberries with one goal in mind: to strengthen their tolerance to water stress.

The researcher from the Agricultural Research Institute (INIA) worked together with the company MipAgro and with the support of the Regional Government of Maule, to develop a product for foliar application. In a laboratory, they evaluated the application of different hormonal formulations to blueberry plants that maintained a water supplementation of 100%, 50% and 25% of their field capacity to test their physiological response. The two formulations with the best results on the physiological indicators of plants under stress conditions were selected, increasing the tolerance of the plant to the limitation of water supplementation. 

"As important as achieving a better plant response to these stress conditions, was that the fruits maintain optimal quality," said Mr. Balbontín. For this reason, he addressed the evaluation of the effect of the previously selected formulations on the organoleptic characteristics of the fruits in an orchard in the town of Parral, Maule region, with the same water supplementation regimens. 

Different variables related to fruit quality were measured. For example, the diameter of the fruit is especially affected by the low availability of water, as can be seen in graph 1. A severe lack of water supplementation can affect at least 10% of the size of the fruit. However, although the use of formulations did not affect this parameter in well-watered plants, it was able to maintain values ​​similar to those of the control group in conditions with 50% less water. 

The compound has proven to be effective in increasing the resistance of the blueberry plant to drought and also improving the firmness, flavor and size of the fruits.

The lack of water causes the plant to partially or completely close its stomata to prevent water leakage, limiting the entry of CO2 into its system. This causes that there is less energy in the plant, less sugars, the production of the plant is reduced for the current and future seasons, and the quality of its fruits decreases.

Hormonal inducers, the main component of the product, are jasmonic acid and abscisic acid, elements that are naturally produced by the plant to initiate defense mechanisms in a stress situation. Both compounds are already part of some products for other fruits, which are artificially synthesized and then applied without affecting the safety of production. 

The combined effect of jasmonic acid and abscisic acid allows the plant to activate defense systems that research has shown are efficient in avoiding the consequences of drought. Jasmonic acid increases tolerance to drought, salts, freezing and increases the accumulation of anthocyanins. In addition, it contributes to the degradation of chlorophyll, whose concentration increases in dehydrated plants.

Finally, abscisic acid induces an increase in the production of waxes, which act as a waterproof layer, allowing the stomata to open to absorb CO2, without the plant losing too much water. In addition, the wax reflects the sun's rays, contributing to lower its temperature.

The results of the research carried out by Dr. Balbontin together with MipAgro allowed us to observe that the percentage of soft fruits increases as the campaign progresses, observing that in the first harvest this value reaches 5%, however 

In the fourth harvest this value is increased to 35% of the total harvested. The use of hormonal inducers allows to improve the firmness of the later fruits, lowering this percentage to 8%, in the best of results.

This not only allowed them to conclude that the inducers help drought tolerance, but also improve fruit quality in cases of complete water replacement and deficit. 

Given the promising results, Blueberries Consulting spoke with Cristián Balbontín about the future of his product and the blueberry industry in Chile.

What do you think the future drought scenario will be like for blueberries? With what strategy should this scenario be faced?

We have to observe the trend of the last 12 years and how the water contribution has decreased or the Isotherm has increased, so we have less snow deposits. That condition is very unlikely to improve as long as we have the La Niña phenomenon, which has become much more persistent. This scenario will require that we focus on producing accurately. There are a series of factors that need to be studied to effectively know how much we have to contribute, what the plant is spending and what it needs to produce. Therefore, it is necessary to be more precise in the use of resources and point to strategies that allow us to increase the quality of the fruits both at harvest and during storage.

Since you mention the post-harvest, did you study the behavior of the treated fruits during this productive stage?

This year we will evaluate the quality of the fruits treated with these inducers during storage. However, our hypothesis is that if we have a better quality at harvest, it can be maintained. This is supported by our experience with cherries, where the synthesis of fruit cuticular compounds is increased, making it more tolerant to dehydration. And on the other hand, thanks to this increase in terms of firmness and acidity, they will be able to maintain their condition for longer.

What strategy should we follow to prepare for drought and not repair its consequences?

It is a complex question, but I believe that valuable work is being done in terms of increasing the efficiency of water use, through the use of substrates for example, or evaluating the use of covers on crops. More research is needed to support the industry and national producers. I believe that instances such as the Blueberries Consulting seminars, for example, give the option of knowing the new advances that are being made in different areas. There are many professionals doing research regarding the efficiency of nutritional compounds; irrigation, harvest or post-harvest strategy; of the behavior of varieties and production systems. Research is ongoing and further research is required. Therefore, a more attentive look is required in terms of the importance of research to support development.

One of the qualities of abscisic acid was that it increased resistance to salinity. Could the investigated formulation be useful considering the future use and obtaining of water?

We need to explore it. This has potential but more research is needed on this. Both salinity stress and drought stress have cellular mechanisms that are similar. It is very interesting to evaluate under what ranges salinized water could be used, without affecting the quality of the fruits and the life of the plant. I believe that the hormonal inducers that we have tested could also be evaluated in such a condition. 

In times of crisis, it can be difficult to invest in science that does not give an immediate result. If we want to be the best producers in terms of fruit quality, we need to develop technologies that aim to do so. We need to create this image that Chile is quality fruit, and to do so we need to implement, investigate, develop more things here.