Morphological Trait and Maturity Group Relations with Digestibility of Orchardgrass

Abstract

Time and labor could be saved in initial screenings if plant breeders had better information on the relationship of morphological traits and of maturity groups to forage quality. This study was conducted to investigate these relations in orchardgrass (>Dactylis glomerata L.). Fifty clones from two maturity groups (anthesis differed by 8 d) were selected divergently for leaf‐blade width, leaf‐blade length, tiller number, growth habit, and seed weight. Space‐planted clones were harvested on a common date in spring (near anthesis of the late group) and summer (after 5 wk of regrowth), and were separated into plant parts before determining in vitro digestible dry matter (IVDDM). Anatomical characteristics were examined for narrow‐ and wide‐blade clones from the two maturity groups. Samples were stained with safranin to identify lignified cell walls, and cross‐sectional areas were quantified by image analysis. Leaf‐blade width was most consistently associated with IVDDM. Wide‐blade clones of the late group were more digestible than narrow‐blade clones during spring growth, but little difference existed during summer regrowth. Differences in digestibility were greatest in stems of reproductive tillers (≈8%). Wide‐blade clones had the same or morelignin in stems than did narrow‐blade clones, but wide‐blade clones had less lignin as a percentage of cross‐sectional area than did narrow‐blade clones. Differences in IVDDM between maturity groups were also most evident during spring growth, when stems of reproductive tillers in the late group were 16% more digestible than those in the early group. Thus, selecting for wide blades and late maturity can be an effective method for initial screening for high digestibility in orchardgrass germplasm.