Characterization of maize genotypes developed under nitrogen stress and the inheritance of the efficiency in using this nutrient / Caracterização de genótipos de milho desenvolvidos sob estresse de nitrogênio e herança da eficiência de uso deste nutriente




Nitrogen is one of the elements most demanded by maize crop, as well as the nutrient that most burdens the agricultural production, since in a wide part of the arable soils it is not available at the amounts necessary to high productivity, therefore requiring supplemental applications. In addition, the commercial maize cultivars are highly dependent from nitrogen fertilization, because they were developed for cropping under optimized environments, so they are not well adapted to the conditions with low N availability. So, the objectives of this study were: to promote a better characterization of the maize lines developed in nitrogen-poor soils; to determine the inheritance patterns of either the efficiency in using N and the response to this nutrient application, concerning to both general and specific combination abilities; and to investigate the behavior of the genotypes, relative to the adaptability and stability in contrasting environments for availability of nitrogen. According to the results, the conclusions were drawn as follows. The efficient lines tend to produce efficient and responsive hybrids provided with general adaptability and satisfactory stability. Both addictive an nonaddictive genetic effects for productivity of grains were important under nitrogen-poor and rich environments. However, the genetic productivity control differed in the contrasting environments concerning to the availability of N, whereas the tendency of the importance of the addictive effects relative to the effects of the genetic complementation varied among the groups of the genotypes under evaluation. The decomposition of the adaptability parameters by Eberhart and Russell (1966) into effects of CGC and CEC rather provided a better understanding of the inheritance for either adaptation to N-poor environments and the response by cultivars to the application of this nutrient. The use of the Pi statistics (Lin &Binns, 1988) made possible the identification of the superior genotypes for both efficiency and response to N, as well as the wide adaptability and satisfactory production stability. The population CMS 59 showed to be the most promising for extraction of efficient lines in using N and provided with high frequencies of alleles favorable to the production of grains under N-poor environments. However, some lines with high CGC estimates and showing good specific combination abilities with lines of CMS 59 were found in all populations under evaluation. Thus, for the development of cultivars that would efficiently use the nitrogen, it is proposed to evaluate the genotypes under N-poor environments, and later the obtainment of hybrid progenies only from the lines more adapted to N-deficiency stress in dialleles or top-crosses for more detailed evaluations. This scheme would provide resource economy due to the decreased number of progenies under test.


melhoramento genético melhoramento vegetal breeding nitrogen nitrogênio qtl milho maize qtl

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