Déficit hídrico em plântulas de milho: aspectos morfológicos e moleculares

Abstract

Maize (Zea mays L.) is the third most consumed cereal in the world and ensure the productivity of this crop under water deficit is fundamental to world food security, especially in the context of global climate changes that lead to an increase in the frequency of episodes of drought. Developing water deficit tolerant maize varieties is an effective way to reduce yield losses. However, the breeding process is only possible in the presence of genetic variability. Varieties of creole maize (landraces), maintained by small farmers, are an important source of genetic variability. For the efficient use of this variability it is necessary to characterize the response of these plants under drought condition. Also, studies to identify mechanisms and candidate genes associated to water deficit tolerance is another strategy to help breeders. The autophagy process is the major mechanism of degradation and recycling of cytoplasmic constituents, including proteins, lipids, nucleic acids and whole organelles. This mechanism is associated with the maintenance of cellular homeostasis, adaptation to stress and immune response, besides promoting programmed cell death in certain situations. Considering the critical role of autophagy in development and stress responses, a better understanding of this mechanism in maize under water deficit can lead to beneficial agricultural applications. Based on the above, this study aimed to characterize the response to water deficit in maize varieties and to study the transcriptional profile of ATG genes from seedlings submitted to this condition. In this study it was verified that a negative effect of the water deficit on the germination and initial development of the seedlings occurs when the osmotic potential of -0.2 MPa is applied, however, there were no marked differences among the evaluated varieties. At the osmotic potential -0.6 MPa or higher there are no survival conditions after germination. Considering the transcriptional profile of ATG genes, there is a variation in the behavior and accumulation of transcripts of the genes according to the variety, the environmental condition and the analyzed tissue. Based on the results obtained it can be suggested that the autophagy process is involved in the response to the water deficit. The results obtained in this study bring new perspectives for maize improvement aiming at tolerance to water deficit.