GENOTYPIC CORRELATIONS IN FORAGE MAIZE .1. RELATIONSHIPS AMONG YIELD AND QUALITY TRAITS IN HYBRIDS

In European forage maize (Zea mays L.) breeding populations little is know about the interrelations among important target traits. The present study was undertaken to estimate coefficients of genetic correlation among eight yield and forage quality characters in a representative sample of genotypes and environments. Sixty-six single crosses produced from 11 flint and 11 dent inbred lines by an incomplete factorial mating design were evaluated in 1983 and 1984 at three locations in West-Germany. Highly significant genetic variation occurred for dry matter yield (DMY), dry matter content (DMC), metabolizable energy yield (MEY), metabolizable energy content (MEC) of stover and forage (forage = ears plus stover), and ear proportion in total dry matter (EPD). Moderate negative genetic correlations were found between DMC and DMY (-0.54**) as well as between MEC and MEY (-0.47**) of forage. MEY of forage was very closely associated with DMY of forage (0.97**) and somewhat less with stover DMY (0.92**) and MEY (0.89**), but only loosely with MEC of stover (0.33*) and negatively with EPD (-0.76**). MEC of forage, on the other hand, was strongly correlated with EPD (0.84**), moderately with DMC of forage (0.73**) and ears (0.62**), whereas no relationship existed with MEC of stover (0.04). The correlation pattern was similar whether MEC refered to dry or fresh matter, but changed considerably, if calculations were based on maturity-corrected data, i.e., after adjusting for genotypic differences in total DMC. Metabolizable energy content of forage then was moderately associated with EPD (0.66**) and additionally with stover MEC (0,45**). We concluded that selection for high DMY is the most efficient way to indirectly improve MEY in silage maize. Within a given maturity group, EPD and stover MEC are the main quality traits and should be considered jointly in selection.