Aluminum reduces the crop's yield and increases costs with soil correction. So far, only one single gene had been identified as responsible for the aluminum tolerance in maize. If proven, the discovery opens possibilities of using gene combinations in new cultivars . By reducing costs, aluminum-tolerant maize cultivars could benefit from smallholdings to large farms. Embrapa scientists partnered with universities and research institutes in Kenya, Africa, and identified new genes that potentially control tolerance to aluminum, using maize genotypes collected in acid soil regions of Kenya. If the discovery is confirmed, it will allow advances in the development of new cultivars, which will count on a more robust collection of genes, granting plants higher resistance to the toxic effects of aluminum. The ZmMATE1 gene is so far the only one characterized in maize to be proved to be tolerant to this element. “We concluded that the aluminum tolerance in the maize lineages from Kenya is not conferred by the ZmMATE1 gene, and also that the higher allele of this gene is not present in other genotypes of highly aluminum-tolerant Kenyan maize”, informs Cláudia Teixeira Guimarães, s, a researcher at Embrapa Maize and Sorghum. The scientist reportts that the ZmMATE1 gene had been identified in another study by the same Brazilian team involved in the new discovery. The work was carried out in partnership with researchers from the University of Cornell and from the United States Department of Agriculture (USDA). In ZmMATE1's case, Guimarães explains that it codifies a citrate carrier, a substance that is released in the roots and protects them from the toxic effects of aluminum. The new study was kickstarted by the international partnership between Embrapa Maize and Sorghum and the University of Moi (MU),in Kenya, with funding from the McKnight Foundation. The second stage of the project received funds from the Generation Challenge Programme. The results were published on the journal Scientific Reports. Pathways for new aluminum-tolerant materials For the researchers, the identification of new genes potentially involved in aluminum tolerance, besides the ZmMATE1 gene, would make the combination of different genes possible, and increase the level of tolerance in maize cultivars. “Embrapa has specific markers and sources to be used in the assisted breeding of the ZmMATE1 gene. An efficient strategy to increase the aluminum tolerance in the maize lineages from Kenya and other countries would be the use of those genetic and molecular tools for the assisted selection of the ZmMATE1 gene”, analyzes Guimarães. The genes present in the Kenyan lineages have small effects on aluminum tolerance in their progeny. The scientist undescores that further studies are necessary for the validation of such effects and for the development of specific markers for the selection of such new genes. “Thus the use of these genes is still far from assisted breeding programs, but new scientific possibilities have been opened”, the researcher celebrates. Aluminum reduces maize productivity The scientists explained that maize production is quite reduced by aluminum toxicity (Al) in acid soils. This type of soil covers approximately 50% of global arable lands, including the Brazilian Cerrado, the biome responsible for a large portion of the country's maize production. In those soils, the rhizotoxic form of Al, Al3 +, becomes predominant in the soil solution, which harms plant root systems. Aluminum toxicity hinders the roots' exploration of the soil, reducing their water and nutrient collection and, consequently, the production of grains. The problem of low pH in the soil can be minimized by liming, which is more efficient in the arable layers of the soil, while correcting acidity deeper into the soil is more difficult and costly. “Despite being common in agriculture, soil correction techniques increase production costs and are unaffordable for many smallholders in developing countries. Thus, a sustainable solution to increase grain yield in acid soils can be obtained by associating soil fertility management practices with the adoption of aluminum tolerant cultivars”, states Cláudia Guimarães. In Brazil, around 70% of the maize production occurs in the second harvest of multiple-cropping regimens, whose productivity is highly dependent of the rainfall. “Increasing aluminum tolerance in maize cultivars is a genetic strategy that contributes to the deepening of the plant's root systems in areas where aluminum saturation prevails in subsurface layers”, the researcher explains. Acid soils coincide with maize crop areas in Kenya, in addition to their occurrence in agricultural regions of South America, Africa and Asia. “Thus, aluminum tolerance in maize cultivars will provide an increase in production stability for several segments of farming: from large-scale cultivation of maize as a second crop in the Brazilian Cerrado to subsistence cultivation in smallholdings in Africa”, the scientist concludes. Translation: Mariana Medeiros