First results from a pyramidal recurrent selection system for breeding maize silage

The pyramidal recurrent selection system which is presented for breeding ma ize silage is designed to enhance variety development by preparing elite po pulations. From an early synthetic dent, two synthetics were developed: the 'base' synthetic with a low selection rate and the 'elite' synthetic with a high selection rate. Two cycles of recurrent selection with tester were a chieved through this system, using multitrait selection with one-year evalu ation of dry matter yield and dry matter content in three locations. The me an of 'elite' synthetic was 2.7% better than 'base' synthetic for dry-matte r yield in the second cycle. Genetic variance of 'elite' synthetic appeared to be about 50% of that of 'base' population for dry matter yield in cycle 2 and for dry matter content in both cycles. Genotype x environment intera ction variance was the same for both types of populations. Thus, strong dif ferences in genetic variances were associated to relatively small differenc es in means. Results are discussed in terms of the effects of selection int ensity, multitrait selection and genetic drift. ((C) Inra/Elsevier, Paris.)