Divergent Selection for Anthesis Date in Annual Ryegrass
- Scott D. McLean and
- Clarence E. Watson
Anthesis date is the major factor controlling distribution of forage yield and quality of annual ryegrass (Lolium multiflorum Lam.) in the spring. This study was initiated to evaluate variation and selection response for anthesis date and to measure correlated responses in annual ryegrass. Four annual ryegrass cultivars were evaluated for heading date, anthesis date, spikelets per spike, and florets per spikelet over 3 yr in the field at Mississippi State, MS. Only spikelets per spike and florets per spikelet, showed significant cultivar × year interactions. Differences among cultivars were observed for all four characteristics. Two cycles of phenotypic recurrent selection for earlier and later antbesis date were performed on each cultivar. Response after two cycles of selection for late anthesis in the early cultivar, Florida 80, was greater (11.1 d) than selection for early anthesis (6.0 d); however, response to selection for early anthesis in the late cultivar, Marshall, was greater (4.8 d) than selection for late anthesis (2.7 d). The tetraploid, ‘Multimo’, exhibited similar responses to selection for both early and late anthesis date. Late selections within each cultivar showed increased numbers of spikelets per spike compared with the respective unselected parent population. Number of florets per spikelet decreased in most selected populations compared with the respective unselected parent populations. There appeared to be sufficient genetic variation after two cycles of selection to allow for additional gain from selection for anthesis date in most populations.
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