<b>The behavior of maize hybrids generated from contrasting progenies regarding the use of nitrogen

Abstract

ABSTRACT. The purpose of this study was to evaluate the performance of maize hybrids synthesized from contrasting genotypes with regard to the use of nitrogen that were selected for their performance in topcrosses. Sixty-seven S 0:1 progenies derived from the germplasm bank of Ufla were evaluated in topcross combinations with two testers at two nitrogen levels. The six progenies with the greatest tolerance and responsiveness to nitrogen (RT) and the five with the least tolerance and responsiveness (R n T n ) were selected and, were, afterwards, crossed in a complete diallel, for a total of 55 hybrid combinations. The following genetic parameters were estimated: genetic variance among the hybrids ( 2 G  ), broad sense heritability in the mean of the hybrids, and selective accuracy ( 2 g g r ). It was observed that the genetic parameters were greater in the environments with available nitrogen and that the early selection by performance in topcrosses of progenies tolerant to low N levels may not be made with high intensity. The hybrids tolerant to low N levels were obtained by crossing contrasting parents.Keywords: plant breeding, abiotic stress, Zea mays.Comportamento de híbridos de milho sintetizados a partir de progênies contrastantes em relação ao o uso do nitrogênio RESUMO. O objetivo deste estudo foi avaliar o desempenho de híbridos de milho, selecionados pelo seu desempenho em topcrosses e sintetizados a partir de genitores contrastantes em relação ao uso do nitrogênio. Sessenta e sete progênies S 0:1 derivadas do banco de germoplasma da Ufla, foram avaliadas em combinações de topcross com dois testadores em dois níveis de nitrogênio. As seis progênies com maior tolerância e responsividade ao N (RT) e as cinco não tolerantes e não responsivas ao N (RnTn) foram selecionadas e posteriormente cruzadas em esquema de dialelo completo, resultando em 55 combinações híbridas. Os seguintes parâmetros genéticos foram estimados: variância genética entre os híbridos ( 2 G  ), herdabilidade em sentido amplo na média dos híbridos e acurácia seletiva ( 2 g g r ). Observou-se que os parâmetros genéticos foram maiores nos ambientes com disponibilidade de nitrogênio e que a seleção precoce com base no desempenho de híbridos topcrosses oriundos de progênies tolerantes a baixos níveis de N não pode ser feita com alta intensidade. Os híbridos tolerantes a baixos níveis de N foram obtidos pelo cruzamento de pais contrastantes.Palavras-chave: melhoramento de plantas, estresse abiótico, Zea mays.

Prospecting of popcorn inbred lines for nitrogen use efficiency and responsiveness1

“…According to Bolaños & Edmeades (1996), a yield reduction of 20 to 30% in abiotic stress conditions, compared to non-stress conditions of the same genetic set, is considered indicative of stress. Although the reduction observed in the present study was slightly lower than the recommended range, the results obtained were higher than those reported by Guedes et al (2015) and Heinz et al (2019), who observed yield decreases of only 13% and 16%, respectively.…”

“…(CV e ) obtained under N stress were higher than those observed under conditions of high N availability for GY and PE, as shown in Table 3. This increase in CVe due to N stress is consistent with findings from other studies on corn (Bänziger et al, 1997;Santos et al, 1998;Guedes et al, 2015;Almeida et al, 2018;Torres et al, 2019) reported in the literature. One possible explanation for this difference in CV e is that in environments with a high supply of N, soil deficiencies are corrected through fertilization.…”

Germination under stress simulation and image analysis as tools for water deficit phenotyping of maize

“…Although water deficit is a complex characteristic, it must be understood for improving plant breeding (Cattivelli et al, 2008). Guedes et al (2014) indicated that for obtaining superior genotypes, the use of diverse characteristics can be a better tool. It has also been indicated for reducing costs and labor, with accurate results (Sousa et al, 2015).…”