Qualidade de sementes de milho e soja armazenadas após inoculação com fungos pela técnica de condicionamento hídrico

Abstract

The present study had as objective to evaluate the physiological quality of the seeds of soybean and maize artificially inoculated by Phomopsis sojae and Stenocarpella maydis respectively and the viability of these fungi during six months under two storage conditions. The seeds were inoculated by the water conditioning technique, which consists of maintaining the seeds on the fungal colonies developed in BDA medium, plus mannitol, contained in aluminum trays. The seeds remained for three time periods, 36, 72 and 108 hours, which corresponded to the different inoculum potentials P36, P72, P108 and the control treatment P0 (non inoculated seeds). Inoculated and non inoculated seeds were submitted to two storage conditions, cold and dry chamber (10ºC and 50% RH) and natural condition (laboratory), being analyzed every 30 days for a period of 180 days. The quality and viability of the seeds were analyzed by health, germination and vigor tests (accelerated aging - EA, electrical conductivity - EC). Under natural conditions, a reduction in the incidence of S. maydis was observed in maize seeds of 18.5% in P72 inoculum potential and 80.5% in P108 potential. As the incidence of the fungus decreased during storage, there was a slight increase in seed germination percentage. The vigor tests confirmed the seed performance, as observed by the standard germination test. The accelerated aging test showed an increase of 19.5% in potential P72 and 25% in potential P108. By the electrical conductivity test there was an increase in the value of this variable of 46%, in the inoculum potential P108. In cold and dry chamber environment the incidence of S. maydis showed a similar tendency to the natural environment, but with smaller reduction when compared to the natural condition. In turn, germination presented the same upward trend in both storage environments. Like the natural environment, seed vigor showed similar values in the cold and dry chamber. For the Phomopsis sojae - soybean pathosystem the incidence of the fungus tended to maintain the initial values in cold / dry chamber condition. For the natural environment there was a decrease in the incidence of the fungus at 180 days of 88% (P36), 28% (P72) and 69% (P108). The germination percentage in the cold / dry chamber presented an average reduction of about 67% among inoculum potentials, and in natural environment 64%. Seed vigor evaluated by accelerated aging presented results similar to standard germination. On the other hand, the vigor evaluated by the electrical conductivity was kept at the same initial levels.