Morphogenic and structural responses of ryegrass cultivars under continuous stocking by beef heifers

Respostas morfogênicas e estruturais de cultivares de azevém pastejado por bezerras de corte

Most studies on ryegrass cultivars emphasize forage production and nutritional value, whereas morphophysiological differences, critical for optimizing grazing management, remain poorly understood. This study evaluated the morphogenic and structural responses of different ryegrass cultivars (Lolium multiflorum Lam.) under continuous stocking. The experiment used a randomized block design with repeated measures over time and three replications. Treatments consisted of three ryegrass cultivars: one diploid (Bolt) and two tetraploids (Bill Max and Selva), continuously grazed by beef heifers. Structural characteristics (canopy height, forage allowance, leaf blade allowance, forage mass, and leaf blade mass) and morphogenic characteristics (leaf appearance, expansion, and senescence rates, phyllochron, and leaf lifespan) were evaluated using the marked tiller technique. No differences were observed among the cultivars for the structural characteristics evaluated. However, Bill Max exhibited a shorter phyllochron than Bolt and Selva, indicating lower thermal requirements for leaf emergence, along with higher rates of leaf appearance, expansion, and senescence. These morphogenic differences among ryegrass cultivars underscore the importance of cultivar-specific grazing management strategies. Among the evaluated genotypes, tetraploid Bill Max was distinguished by its shorter phyllochron and greater leaf production efficiency.

Key words:
Lolium multiflorum ; leaf lifespan; phyllochron; leaf appearance rate; ploidy level