Caracteres Fisiológicos e Agronômicos em Progênies Interpopulacionais de Milho Selecionadas sob Condições de Déficit Hídrico

Maize: Key agricultural crop in food security and sovereignty in a future with water scarcity

“…Higher sensitivity in the reproductive period occurs because of the physiological processes related to zygote formation and the beginning of the grain filling, in addition to the high transpiration caused by the maximum leaf area reached at this stage of development (Bergamaschi & Matzenauer, 2014). Water stress in maize plants causes delay in the emergence of stigmata, resulting in an increase in the interval between male and female flowering, and also in high percentage of aborted zygotes after fertilization (Bernini et al, 2016). The most prominent responses of plants to water deficit are the reduction in leaf area production, stomatal closure, senescence acceleration and leaf abscission.…”

“…When under water stress, plants can respond by developing mechanisms of morpho-anatomical, biochemical, physiological and molecular adaptation (Taiz & Zieger, 2013). Physiological alterations correspond to changes which occur at the cellular level, such as leaf water potential, stomatal conductance and chlorophyll content; morpho-anatomical alterations correspond to the increase in the interval, in days, between female and male flowering, accelerated senescence of culms and leaves, reduction in plant height, prolificacy, number of branches of the tassel and total dry matter (Bernini et al, 2016). The physiological alterations which guarantee yield under stress conditions are: lower reduction in water potential, reduction in CO 2 assimilation rates, prolonged stomatal closure, higher chlorophyll concentration and deep roots (with less lateral branching).…”

“…The physiological alterations which guarantee yield under stress conditions are: lower reduction in water potential, reduction in CO 2 assimilation rates, prolonged stomatal closure, higher chlorophyll concentration and deep roots (with less lateral branching). The lack of water reduces the turgor of the cells and, consequently, their growth, an increase in the synthesis of the abscisic acid (ABA), which induces stomatal closure and reduces CO 2 assimilation (Bernini et al, 2016).…”

“…The genetic variability for the desirable characteristics of maize can be obtained through new combinations and intercrossing of the genotypes (Bernini et al, 2016). The adaptation to the environment with stress occurs when genetic alterations are fixed in the entire population of plants through natural selection or in individuals which undergo a stressful situation and change their physiology or morphology (Bernini et al, 2016). In the genetic improvement of maize in the scenarios of increased water stress, production stability and wide adaptation should be sought, increasing the tolerance (Bernini et al, 2016).…”

Estratégias de melhoramento para tolerância à seca em germoplasma de milho tropical

“…Em estudo de casa-de-vegetação [3] estudaram a variedade IAC Maya Latente e verificaram comportamento produtivo estável nos ambientes de irrigação normal e déficit hídrico, devido à maior sensibilidade (fechamento) dos estômatos, resultando no maior acúmulo de matéria seca total e pouca redução do índice de colheita, em estresse hídrico. É sugerido que a seleção em ambientes ótimos de irrigação não é efetiva na identificação de genótipos superiores para condições de seca, devido à baixa variância genética e herdabilidade da produtividade de grãos [5]. De acordo com [6], duas considerações podem melhorar a herdabilidade e a eficiência da seleção para produtividade sob déficit hídrico e/ou compensar a baixa herdabilidade da produção sob estresse: (1) a condução do campo experimental sob déficit hídrico deve apresentar homogeneidade das condições de umidade do solo e assim reduzir o erro experimental e (2) utilizar populações que contenham variabilidade genética para produtividade de grãos, tolerância a seca e ideotipo de plantas que contenham os caracteres secundários.…”