Simultaneous selection for nutritive value and agronomic traits in timothy (Phleum pratense L.)

Improvement of forage nutritive value through breeding should lead to enhanced livestock productivity but often results in reduced agronomic performance. This study investigated the potential for simultaneous improvement of nutritive and agronomic traits in timothy (Phleum pratense L.). Two unrelated groups were used as the base populations: group A focused on agronomic traits and group N focused on three nutritive traits (low-digestible fiber, water-soluble carbohydrate content, and the ratio of low-digestible fiber to organic cell wall content). Although the two base populations contained few genotypes with both high nutritive and agronomic performance compared with the standard cultivar ‘Kiritappu’, the Cycle 1 populations selected for the traits simultaneously included promising genotypes. The two strains improved via two cycles of selection were superior to the Cycle 1 populations and ‘Kiritappu’ based on a comprehensive analysis of the targeted traits in a yield trial test. However, the nutritive traits of the strain derived from group A were more similar to the Cycle 1 population and ‘Kiritappu’ unlike in the successful case of group N. This may be attributable to the more similar phenotypic distribution of the strain A parental clones to ‘Kiritappu’ compared with that of group N for the nutritive traits. The strain derived from both groups showed high nutritive value with the best yield of all tested genotypes, suggesting the possibility of heterosis for yield. These results indicate that application of recurrent selection simultaneously for nutritive and agronomic traits is likely to provide effective improvement without detriment to important traits.