Liliane Marcia Mertz

Qualidade sanitária de sementes de milho em diferentes estádios de maturação

The objective of the present study was to evaluate the health of maize seeds at different maturation stages. Three inbred maize lines, which served as the female parent to produce commercial hybrids, were used. Plants, which had shown 50% of their stigmas at flowering, were marked to determine the harvest time. Seed harvest began 40 days after flowering and occurred at 4-day intervals up to physiological maturity, which was determined by milk line formation. Seed health was evaluated by the blotter test. To determine the effect of seed health on physiological seed quality, germination and vigor tests (accelerated ageing and cold tests) were done. The results showed that maize seeds had a high incidence of fungi Aspergillus flavus, Penicillium sp. and Fusarium moniliforme, but microorganism incidence decreased as the physiological maturity point was reached. The fungi did not affect physiological seed quality.

Ideal seeds harvest moment of different maize hybrids

The aim of this study was to identify the ideal maize seed harvest moment by different characteristics, as black layer formation, milk line development, seed moisture content and seed dry matter accumulation. Three simple hybrids from Syngenta Company were used in this work; ears from plants in the same development stage were collected, the first harvesting began 40 days after flowering, at four days interval until all seeds in an ear had the black layer formation. The characteristics evaluated were: black layer formation, milk line development, seed moisture content and seed dry matter. Seed physiological quality was evaluated by germination test, cold test, accelerated ageing and electrical conductivity. Results obtained in this study showed that the best indicative to identify the ideal maize seeds harvest moment is milk line stage 4 (75% of solidified endosperm). This stage occurs at different time for each genotype studied, 60DAF to hybrids 1 and 3, and 52DAF to hybrid 2, due to genetic differences among the hybrids.

Punctual mutations in lipoxygenase sequence expressed in black soybean seed coat

Lipoxygenase enzymes are relevant in several characteristics of soybean seeds, such as germination performance, storage capacity and tolerance to infection by microorganisms. In this sense, the study of allelic variations of the genes related to that enzyme may be promising for the development of molecular markers associated with phenotypic characteristics which are relevant to seed physiology. This study aimed to identify mutations in lipoxygenase sequence expressed in black soybean seed coat. After isolation of the sequence of interest by the cDNA-AFLP technique, such sequence was compared with sequences of nucleotides and proteins of the lipoxygenase present in yellow soybean seed coat. Analysis of multiple sequence alignment has shown an expressive number of changes in the sequence of nucleotides, which have resulted in the modification of 13 amino acids in the translated protein. The identification of such mutations widens the possibility for further studies involving the association of these allelic variations with phenotypic differences of interest to seeds physiology.