Microsporogênese em milho forrageiro (Zea mays L.)

Abstract

Among cultivated plants, the maize is the most studied one because its versatility of use. The utilization of maize as silage drastically reduces the costs of cattle production. Data related to cytogenetics aspects were not found for this culture. In breeding programs, commercial hybrids are frequently used as the source of inbred lines to obtain new hybrids. Considering that the maize cultivation is dependent on healthy seeds that, in turn, are dependent on viable gametes, the selection of populations to obtain inbred lines with high meiotic stability could contribute to the formation of new corn silage hybrids adapted to the South Region of Brazil. The meiotic stability of six commercial hybrids of corn silage was evaluated by conventional methods. All of them presented meiotic abnormalities, however in different amounts. Some abnormalities, such as abnormal chromosome segregation and absence of cytokinesis, occurred in all the genotypes, while others, including cytomixis and abnormal spindle orientation or absence of spindles, were found only in some genotypes. The hybrid SG 6010 presented the lower mean frequency of abnormal cells (21.27%), however the higher frequency was found in the hybrid P 30K64 (44.43%). But, when only the frequency of abnormal meiotic products was compared, it drastically decreased for the majority of genotypes, ranging from 7,36% in the hybrid CD 304 to 43,86% in GARRA. Taking into account the percentagem of abnormal meiotic products and, hence, the meiotic stability, only the hybrids CD 304, P 30K64, SG 6010, and P30F53 are recommended to remain in the breeding program to obtain inbred lines to create new hybrids.