Processamento digital de imagem na interpretação do teste de tetrazólio em sementes de Urochloa brizantha

Abstract

The production and use of high quality seeds are important factors for the field establishment of brachiaria plants and the formation of pastures and adequade cover. The seed quality depends on the development of accurate and efficient evaluation techniques and the digital image processing has been used to increase the accuracy of the results and to decrease the time and subjectivity in the evaluation of physiological quality of seeds of different species. The aim of this research was to establish methodologies for digital image analysis in the evaluation of seed viability, by the tetrazolium test and in the vigor of seedlings of Urochloa brizantha cv. Marandu by the GroundEye® system in the S120 and S800 versions. The first experiment was divided into three phases, in the first, a pre-test was carried out with a seed lot for methodological development related to the calibration of the equipment through the capture and analysis of the image in the choice of the best background for reading the viability of the seeds submitted to the tetrazolium test. In the second phase, seed viability was evaluated for nine seed lots of Urochloa brizantha cv. Marandu by the tetrazolium test by image analysis and verified the relationship with the physiological quality of the seeds by evaluating the moisture content, germination, tetrazolium, emergence under controlled conditions, emergence speed index and mass electrical conductivity. In the third phase, the seedling vigor evaluation was carried out, at 7 and 14 days after sowing, of the nine seed lots by image analysis and compared the relationship with the physiological quality, carried out in phase two. In the second experiment, 12 lots of brachiaria seeds were characterized for physiological quality and measured the moisture content, germination, first germination count, germination speed, emergence under controlled conditions, emergence speed, mass electrical conductivity, seed health and X-ray images. A comparison of the viability of the seeds was performed by the tetrazolium test using the conventional, visual method and digital image analysis with seeds packed in acrylic plates with individualized cells in different colors to evaluate the results. It was possible to evaluate the viability of brachiaria seeds submitted to the tetrazolium test by digital image analysis, in individualized acrylic containers of dark blue color. Digital analysis of the brachiaria seedlings vigor, by the length of the root at seven days was possible and correlates with traditional vigor tests. Therefore, digital image processing by the GroundEye® system in versions S120 and S800 with appropriate processes and methodologies provides reliable data on the viability and vigor of brachiaria seeds and seedlings and can be considered an efficient, fast, non-subjective and time-saving approach.