MAIZE CULTIVARS WITH LOW SEED COST IN BRAZIL

– Maize is one of the cereal crops most produced globally. It constitutes one species of most economic interest and provides multiple products with applications in diverse sectors, from animal feed to industrial products and even human food. More and more companies that represent this segment release genetically modified maize hybrids to ensure return on investment, decreasing the supply of conventional (non-transgenic) cultivars available on the market. Seed is one of the main components of the cost of maize production. Thus, farmers that obtain lower yields cannot afford to pay the relatively high costs of the high technology hybrid seeds or improve their production system, but it is possible to obtain satisfactory results through lower seed investments. Therefore, intervarietal hybrids may represent an alternative for meeting the needs of small and medium-sized farmers, with fewer resources for investments in inputs and seeds, and for supplying varieties that meet the needs of the small maize grower. This review presents a history of conventional maize breeding in Brazil and describes the main maize cultivars with low-cost seeds developed by public R&D companies, mainly focusing on the Instituto Agronômico (IAC) as an option for small and medium-sized maize growers in Brazil.


2
Maize is one of the cereal crops most produced on the planet. In the 2019/2020 crop year, Brazil achieved total production of 1.11 billion metric tons, with 35% directed to export, 9.5% to industrial consumption, and 1.1% to human consumption (Paterniani and Fachini, 2020).

Zea mays L. is a monoecious species
with open pollination and has broad natural genetic variability, with approximately 300 races identified. Its favorable cycle and reproduction traits make it a model for genetic studies of allogamous species (Paterniani et al., 2000a). There are very few conventional (non-transgenic) maize cultivars on the market and for human consumption, and this represents a promising niche for public research and development companies.
The high cost of seeds is one of the determining factors in choosing the type of cultivar adopted in low-investment and subsistence agriculture, leading to the use of one's seeds and advanced generations of hybrids (Pacheco et al., 2010). Expenditures on this input can represent around 20% of the value of financing the crop, but it is possible to obtain satisfactory results with smaller investments in seeds.
Due to the immense volume that the maize seed industry represents and, despite high competition in the sector, the maize seed market mainly focuses on serving the central niche of current production, the feed production market.
The companies representing this segment have continuously released genetically modified maize hybrids to ensure return on related R&D investments and market share, reducing the available conventional (non-transgenic) cultivars. In the 2019/2020 crop year, only 10% of all the maize planted was conventional seeds (Abimilho, 2020).
Considering the domination of the seed market by multinational companies, the Brazilian public institutions, such as Embrapa, the Universidade Estadual de Maringá (UEM), the Instituto Agronômico do Paraná (IAPAR), the Instituto Agronômico in Campinas (IAC) (Sawazaki and Paterniani, 2004)  An alternative adopted by the IAC was to direct breeding to the markets of intervarietal hybrids and special maizes for human consumption, such as popcorn and green corn. As Jugenheimer (1958) reported in an extensive review, although intervarietal hybridization proved promising, it was not used commercially due to the difficulty of obtaining seeds. In that same period, hybrid vigor in crossing lines was also studied, where Shull (1908; and East (1909) (Paterniani, 1967).
Conceptually, there are the following types of hybrids: single-cross (obtained through crossing two inbred lines); three-way cross (obtained by crossing a single-cross hybrid with a third line); double-cross (resulting from crossing two single-cross hybrids, that is, coming from the cross between four lines); top cross (cross of a line with a variety); and intervarietal cross, which is the result of crossing two varieties (Sawazaki and Paterniani, 2004).
Intervarietal hybrids are obtained directly by crosses between two or more parent varieties.  The intervarietal hybrid was specially developed to meet the demand of small or medium-sized rural growers that use loweryielding production systems and lack higheryielding seeds, though at prices that do not make their production unfeasible. These hybrids, also found that this occurs (Allard, 1971). According to the Hardy Weinberg law, the allele and gene frequencies of a sufficiently sizeable allogamous population will always be the same in the absence of migration, mutation, and selection (Hallauer & Miranda Filho, 1988;Pugh & Layrisse, 2005).
The cost of producing seeds from F2 or intervarietal hybrids is reduced because the steps of obtaining and multiplying lines are   The study developed by Doná et al. (2009) showed promising F2 populations regarding per se performance, and the yield potential of hybrids from F2 populations as an alternative for commercial maize production was corroborated.

Transgenic Cultivars Total Transgenic Cultivars
Some parent populations stood out with high heterosis values of parents according to the model of Gardner and Eberhart (1966), and three hybrids of high yield and with specific heterosis for grain weight were observed. Bernini and Paterniani (2012)  The method of obtaining hybrids from F2 or synthetic populations uses diallel crosses, primarily through the models of Griffing (1956) and Gardner & Eberhart (1966)  constitute the female rows, and the male rows will be sown with a mixture of seeds from the selected progenies, in the proportion of 3:1 ("Irish Method") (Paterniani, 1978).   to a bird commonly found on marshy lands; the variety is appropriate for planting in floodplains or areas with temporary excess of water and can be used for grain production, fresh corn, and forage. The variety BRS Sol-da-Manhã was formed and selected to meet the farmers' needs with soil stress related to nitrogen. The various selection cycles of this variety were carried out in environments with low natural fertility and a low nitrogen level.

Final Considerations
The maize seed market in Brazil is dominated by transgenic single-cross and threeway-cross hybrid cultivars, with higher seed cost and production technology.
Maize production systems are very heterogenous since they range from highly technified systems to subsistence farming, Maize Program at IAC in 1939. In the state of São Paulo, the peak of maize seed production developed by IAC and produced by CATI was in the 1970s and 1980s. Since then, the monopoly of multinational companies, the crisis of the public system, the scrapping of all public research and seed production institutions, the lack of financial and human resources, and political interests have impeded the maize seed production process.
The scientific community has discussed this scenario for years. Therefore, maize seed production in Brazil should be remodeled and improved toward small growers, and this will only be possible with public-private partnerships and meeting the needs of specific niche markets.