PR - Factors Influencing Ear Initiation And Ear Emergence Development Of Perennial Ryegrass Cultivars At Two Different Latitudes

The objective of this study was to define the relationship between ear initiation (EI) and ear emergence (EE) of perennial ryegrass cultivars at two latitudes. This investigation comprised three treatments (outdoor site at 54oN (CROSS’05), outdoor site at 50oN (MPK’06) and glasshouse at 54oN (CROSS’06)) on a common set of 40 cloned spaced plants of eight cultivars. EI date between MPK’06 and CROSS’05 was similar (+/- 1 day) while EI date at CROSS’06 was earlier (-16 days). Plants at MPK’06 had an EE date eight days earlier than plants at CROSS ’05 and CROSS’06. The interval between EI and EE was longer at CROSS’06 (+19 days) and CROSS’05 (+6 days) compared to MPK’06. Later heading cultivars had shorter period between EI and EE than earlier heading cultivars. A strong relationship between plant EE and EI was found at Moorepark (r2 =0.93) and Crossnacreevy (r2 = 0.94). Predicting cultivar EI date is a key indicator of the timing of sward quality deterioration.