Inoculum potential of Stenocarpella complex and its relation with physiological quality of corn seeds

Resumo

Damage caused by Stenocarpella complex greatly reduce corn yield. This work was carried out to evaluate the relation between corn seeds physiological quality of a susceptible genotype and a tolerant genotype submitted to different S. maydis and S. macrospora inoculum potential, separately. Fungal colonies were grown on BDA plus mannitol culture medium, with water potential adjusted at -1.4 MPa. Seeds were inoculated for 0, 24, 48, and     72 hours. Evaluations were carried through seed health test, germination, germination first count, seedling emergence, speed of emergence index (SEI), cold test without media, and esterase enzyme expression. The highest incidence of Stenocarpella sp. was observed in the susceptible genotype. The tolerant genotype did not show typical structures of Stenocarpella complex at seven days. The increase of inoculum potential of S. maydis and S. macrospora on corn seeds generate physiological quality reduction. This quality reduction can be observed from 24 hours of inoculation for the susceptible genotype. The tolerant genotype was not physiologically affected, regardless the inoculation time to which they were submitted. The esterase analyses helped to differ S. maydis and S. macrospora inoculates and can also differ corn seed genotypes, however the reduction of seed quality observed with inoculation of the fungus cannot be detected only by viewing the bands in the gel.