Fenotipagem para tolerância à deterioração de sementes de milho após a colheita em espigas

Abstract

The challenges faced in the corn seeding industry to ensure the production and commercialization of high-quality seeds are many. One of these challenges is the flow of seeds collected from cobs, from the production fields to their processing, without loss of quality. Corn seeds, harvested on the cob, are subject to deterioration due to high water content, often associated with increased temperature of the seed mass. In the deterioration process there are changes in carbohydrates, lipids, proteins and antioxidant compounds, which influence the physiological quality of seeds. In this process, genetic variability has been observed for tolerance to seed deterioration. Therefore, there is a need for research to develop safe methodologies for the selection of genetic materials regarding seed tolerance to deterioration, at this stage of the production process. In this research, adaptations of the controlled deterioration test were proposed for the phenotyping of corn genotypes for the characteristic of seed tolerance to deterioration, after harvesting on the cob. The expression of proteins in seeds subjected or not to controlled deterioration was also evaluated. For this purpose, genetic materials from the UFLA and Bayer Company corn breeding program were used, which presented genetic variability for this characteristic. The following variables of the controlled deterioration test were evaluated: water content of the seeds during the deterioration process (25% and 35%), drying of the seeds after the deterioration process (with or without drying), exposure time of the seeds in the deterioration process (48 and 72 hours) and seed disinfestation with 1% sodium hypochlorite. In part of the genetic material, the expression of enzymes involved in the respiration process (Malate Dehydrogenase, Alcohol Dehydrogenase, Pyruvate decarboxylase), those involved in oxidative systems (superoxide dismutase, catalase, peroxidase) and also esterase, was evaluated in seeds. alpha amylase and heat resistant proteins. It was concluded that through the controlled deterioration test, on seeds with a water content of 25%, stored for 48 hours at 42ºC, and without disinfestation with hypochlorite, it was possible to classify the corn genotypes in terms of seed tolerance to deterioration, three days after sowing. There was lower expression of the enzyme’s pyruvate decarboxylase, alcohol dehydrogenase, malate dehydrogenase, superoxide dismutase, catalase, peroxidase, esterase, alpha amylase and heat-resistant proteins in corn seeds subjected to the controlled deterioration process, expressions associated with lower physiological quality in deteriorated seeds. The influence of the genotype on the expression of some proteins evaluated in this research was also observed.