The seed represents the main and most important input in agriculture, being indispensable in the production system, acting in the agricultural market as a protagonist of technological innovations. Strong and competitive agriculture cannot be maintained today without an efficient legal framework that ensures this production, without compromising the quality of the seeds produced.
The characterization of a quality seed involves different individual components, which are related to physiological, physical, genetic and health aspects. Together, these aspects will give it high agronomic performance, since the seed contains the embryo within, with the potential to grow and develop into an adult plant.
The physiological aspect of seeds is related to the seed's ability to perform vital and vigorous functions satisfactorily. This influences the uniformity of the initial stand, the plant's ability to develop in the field, productivity and, mainly, the storage period, that is, the longevity that the seed is capable of achieving, without compromising its germination potential.
Physical quality refers to the absence of foreign, inert materials or seeds from other species or cultivars. The occurrence of mechanical damage during harvesting is directly related to physical attributes, which can compromise its quality, and even become a gateway for pathogens and damage the cellular structure of the seed and its performance.
When it comes to genetic quality, the seeds must present varietal purity and representativeness of their genetic material, that is, not present a mixture of other cultivars, in addition to expressing their maximum potential for productivity and precocity.
Seeds with high sanitary quality mean that they are free from pests and diseases such as viruses, fungi, nematodes and bacteria, or when the seed receives chemical treatment, allowing the reduction of infestation by these pathogens. However, choosing a seed with high health favors sowing with greater security and rapid and uniform initial establishment.
All these factors demonstrate the importance of the rural producer knowing the quality of the seeds positioned in his field, thus avoiding uneven emergence in the establishment of the field, possible failures in the stand and the reduction in productivity with the use of low quality seeds, which can reseeding may be necessary due to poor seedling establishment performance.
Considering the consumer market's demand for the use of superior quality seeds, strategic seed quality management becomes an important tool within the production chain. The laboratory stands out as the main source of detailed information about the performance potential of seed attributes, through specialized and standardized tests, helping to identify problems and their possible causes.
Currently, there is a range of quality tests that can be applied to evaluate seeds at all stages of the production process, from the multiplication field to delivery of the batch to the final consumer. Among the tests, we can mention some examples such as: tetrazolium, germination test, accelerated aging, controlled deterioration, electrical conductivity, germination speed index, length of seedlings and roots, cold test, low temperature test and seedbed emergence. Of these, only the germination test is mandatory for the commercialization of seeds of large crops, which is required by the Ministry of Agriculture, Livestock and Supply (Mapa), a minimum standard, which in the case of soybean cultivation is 80%.
Another widely used test that helps rural producers at the time of harvest is the sodium hypochlorite test, which allows the assessment of mechanical damage (tegument rupture), one of the main limiting factors for the production of quality seeds. The principle of the test is for the solution to rapidly swell the damaged integuments (it penetrates under the integument causing the cotyledons to move away). Two samples of 100 apparently intact seeds are used, submerged in a 1% sodium hypochlorite solution for 10 minutes, where the damaged seeds will swell, wash and count the number of swollen seeds, X in %. The time for carrying out the test is very important, because if the seeds are exposed for a longer period, those without damage will also swell.
In addition to mechanical damage being quite harmful to the physical quality of the seeds, another factor that tends to cause the greatest impact during the finalization period of production fields is the high temperature associated with the relative humidity of the air, as well as precipitation, favoring deterioration due to humidity. No less important, we also have the possibilities of associations between climate and nutritional stress in relation to attacks by insects and microorganisms, that is, the seed begins to deteriorate while still in the field. In view of this, it is extremely important to monitor the seed production field in order to monitor the considerable attributes of the seeds and reduce their deterioration, increasing the storage potential that is determined by the initial physiological quality of the harvested seeds.
During storage, seed deterioration cannot be avoided, however the speed of the process can be minimized through appropriate production, harvesting, transport, drying, processing and storage procedures.
Finally, it is worth emphasizing that the production of high germination seeds is not enough, but, to ensure high storage potential and, consequently, adequate performance in the field establishment phase, the objective must be to obtain high vigor seeds and the correct storage under environmental conditions favorable to seed conservation
