How to tackle pests in a changing environment: crop resilience and strategies to overcome the climate crisis

Agriculture might be considered as an ecosystem created by human beings to face its necessities, with a not so good characteristic: its capacity of being resilient to a changing element in the environment is way more reduced than in a natural ecosystem because its biodiversity is highly reduced (Brussaard et al., 2010). With the existing climate emergency, it is vital for humanity to develop more resilient crops to ensure food security. Dramatic changes in temperature, wind, rains, or floods are not only needed to be considered as abiotic stress by themselves but also in terms of the appearance of new pests (Skendžić et al., 2021).

In agriculture, when there is a problem related to the presence of a new pest, two solutions are possible. First, the application of pesticides to kill the pest before it is too late, if possible. There are some issues related to this solution due to the unspecific nature of traditional pesticides, that kill not only pathogens but also beneficial microorganisms, inevitably affecting the yield of the product (Ahemad & Khan, 2013). In addition, some works state that the application of organic substances like copper sulfate, extremely damages the plant cells, producing a plethora of random mutations and being possibly responsible for severe human illnesses (Atha et al., 2012; Coelho et al., 2020). It is necessary for society to understand that all the external inputs applied to the crops have a cost for the plant, for the ecosystem, and consequently for the yield and for humanity, in a higher or lower level. However, the development of extremely specific pesticides is quite difficult to achieve (Josephson, 1983). This is the reason why another type of product can be applied, biostimulants or microorganisms that prime the plant before the pest arrives setting up the defense machinery in advance. In addition, it is important to remark that the plant uses the same mechanisms of recognition for beneficial and detrimental microorganisms (for example CERK1 for the pathogenic fungi and for AM), and partially, the same signaling cascades, which reinforces the idea that everything that is externally applied to the plant has a cost (Miyata et al., 2014). The main advantage is that priming the plant with these chemicals affects less the ecosystem, however, makes that the plant is constantly using energy to produce defense molecules (Romanyukha et al., 2006). As a consequence, the plant is not devoting energy to its growth which reduces the crop yield substantially, however, it does not affect the ecosystem as badly as the traditional pesticides. The latter product has also another drawback, which is that the farmer has to apply it before the pest appears, which is not always possible and it requires a considerable amount of money.

The second solution is to develop resistant plants to given pests. Traditionally, farmers have selected the varieties that were resistant to the thread, however, this might suppose a decrease in productivity. Then, classical and molecular breeding technologies tried to obtain new varieties as productive as the sensitive ones but, indeed, resistant to the pest. These techniques have some drawbacks; one could be the “linkage drag” in which the resistance variety is not only carrying the resistance gene but also an unwanted genetic region that affects somehow productivity (Peng et al., 2014). Obtaining a new resistance variety using these techniques, takes years to be accomplished and, I think, society cannot afford this. Novel strategies for biotechnological improvement like the use of CRISPR/Cas9 technique have to be reconsidered for the European union since it will significantly shorten the time for obtaining a new variety (Wang et al., 2019), saving money and lives (even though the possible presence of CRISPR/Cas9 off-targets, it will still shorten the time for obtaining new varieties). Shorten the time is crucial since lots of cultivars, like olive tree, take up to 6 years to be productive (imagine if obtaining the variety also costs years).
Since both the plants and pathogens are constantly evolving to be able to ‘win’ the fight, fast techniques are going to be needed for the agriculture to face new threads. In terms of the durability of the plant resistance, it is quite difficult to achieve it since the pathogen evolution is also constant (Anderson et al., 2010). Thus, it is necessary to use fast breeding techniques to overcome the pathogen evolution and the new threads that are going to appear due to the climate emergency. We need to obtain in a fast way, resistant varieties (CRISPR/Cas9 techniques might ensure this) but we might need to use some chemicals when the plant resistance starts to disappear. In addition, there is a need to change the European regulations since nowadays it is approved the use of organic pesticides like copper sulphate that produces severe DNA damage (off-target mutations) and pollutes the environment, but the directed mutagenesis techniques like CRISPR/Cas9 is banned because of the possible off-target mutagenesis production. Concluding, this article aims to remark the importance of study the plant-microbial interactions to develop specific pesticides and the establishment of new genome editing techniques for proper face the climate crisis today and in the future.

References.
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