Pre-breeding: a tool against threats in agriculture

Edição XXIII | 05 - Set . 2019

Liliane Henning - | Alexandre Nepomuceno -

    Plant breeding has significantly contributed to increased productivity of agricultural species. Through artificial crosses and selection methods, new, more productive cultivars with important agronomic characteristics are offered annually. This process has led, over the years, the replacing of poorly productive old materials with improved varieties that generally have a narrower genetic base. Despite the numerous advantages of breeding, this selection based primarily on yield potential can lead to the loss of valuable genes present in unimproved materials, such as those that confer resistance to disease and abiotic stresses, for example.

    In order to preserve this biodiversity, germplasm banks were created, places where seeds of all kinds of plant species are stored, including unimproved and also exotic germplasm. These germplasm banks are gene reservoirs that the breeder can use to solve specific problems, such as susceptibility to a particular disease. In Brazil, Embrapa Genetic Resources and Biotechnology has one of the largest germplasm banks in the world, which contains a large number of species, especially those of agricultural importance.

    However, the retrieval and transfer of these genes of interest, present in an ancient or exotic material, to a modern variety can take years if there has been no previous improvement work. This is why so-called Preventive Improvement becomes so important. Preventive breeding aims to identify genes and traits of interest present in exotic or unimproved germplasm by incorporating these genes into a more current and more productive variety. With this, it is possible to shorten the genetic distance between these wild species and modern varieties, facilitating the breeder’s work, which in the face of a new pest or disease, can quickly develop resistant cultivars.

    This preventive breeding work is essential, for example, to generate varieties resistant to agricultural pests (insects and diseases) of quarantine importance still missing in the country, which, if introduced into the national territory, can cause severe damage to agriculture. These organisms can be transported over long distances by land, sea and air, as they are easily propagated pests. Thus, at any time, there is a risk of these pests entering Brazil, which may be present in neighboring countries of Latin America, or even more distant regions such as North America, Europe, Africa, Asia and Oceania.

        Preventive breeding aims to identify genes and traits of interest present in exotic or unimproved germplasm by incorporating these genes into a more current and more productive variety.

    In general, preventive breeding consists of different steps. Initially, the search for potential pest resistance genes in germplasm banks, is performed. In a next step, crosses are made between these unimproved genotypes carrying resistance genes and an elite lineage, which contains characteristics of a modern variety. The next step is to select the plants that acquired these resistance genes. For this, biotechnology tools, such as the use of molecular markers, can be used, facilitating the introduction of these genes in modern varieties. Finally, the selected varieties are tested in countries where these quarantine pests have already been identified and occur endemic in those countries.

    Current advances in biotechnology have made important contributions to preventive breeding activities. The reduction in DNA sequencing costs facilitates the discovery of genes and genomic regions present in unimproved germplasm that are associated with important traits. Combined with this, gene editing tools, especially CRISPR, could facilitate the rapid insertion of these genes into current germplasm.



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