Rasgo no tegumento em sementes de soja suas causas e consequências

Abstract

The visual characteristics observed in plants and seeds are known as phenotypic traits, which result from the interaction between genetic factors, intrinsic to each species and cultivar, and the environment in which they are grown, the seed coat cracking in soybean is an example of this. The occurrence of this physiological disruption has generated insecurity among seed producers and farmers, due to possible problems related to seed quality when it occurs. Because of that, the objective of this work was to verify the causes and effects of the cracking on the quality of the seeds and to characterize, in a structural and chemical way, the coat with cracking. For this, the work was divided into three experiments. Experiment I - Chemical and anatomical characterization of soybean coat with physiological disruption: used 5 lots of soybean seeds, of three different cultivars, which present cracking in the coat and one lot of a cultivar that does not present cracking, as a control. Each lot was separated into seeds with intact coat and with coat cracking, after manually removing the coat from the seeds, which were used to evaluate the chemical composition and anatomy of the coat with and without cracking. Experiment II – Genotype-environment interaction for the cracking characteristic of soybean seed coat: using three seed lots with 100% cracking which were sent for cultivation in five locations, in the states of RS, PR, MT and BA. At the end of the crop cycle, yield components and their correlation with the percentage of cracking in the coat of the produced seeds were evaluated. Experiment III – Implications of soybean seed coat cracking on the quality of seeds: using 3 lots of soybean seeds, each manually segregated in 3 portions: Original lot, seeds with intact coat and with coat cracking, which were stored at temperatures of 15°C and 28°C for 270 days. At 45-day intervals, vigour and viability were evaluated by the tetrazolium test, first germination count, germination test, accelerated aging and conductivity test, and every 90 days the emergence in soil. With the information collected in the experiments, it is possible to conclude that the coat cracking occurs preferentially in the thickest places and presents itself as a result of the contents of phosphorus and calcium, and consequently of magnesium. The cracking in the soybean seed coat is a phenotypic consequence, and seems to be favored in environments with high availability of water and nutrients during seed formation, combined with high temperatures. In addition, the seed coat cracking reduces the storage potential of the lots, especially when the seeds already show signs of deterioration in the place.