PREANTHESIS AND POSTANTHESIS DURATION OF 2-ROWED BARLEYS IN RELATION TO STABILITY OF GRAIN-YIELD AT HIGH-LATITUDES

A short growing season and consequent demand for early maturing cultiv ars are the main factors limiting yield potential of two-rowed barley in Finland. This study was undertaken to compare spikelet production o f ten two-rowed barleys which differed in duration of pre-anthesis and grain filling, and to clarify how reduced duration of these phases co ntributes to stability of yield formation under long-day conditions. S pikelet set declined but number of fertile spikelets increased with de crease in the length of the pre-anthesis phase. Breeding for a short p re-anthesis phase may not necessarily reduce grain yield, but could le ad to instability in yield formation. In selecting breeding lines with a short pre-anthesis phase, a pre-anthesis phase to maturity class ra tio (P:M ratio) of 0.58 was found to be suitable under Finnish conditi ons, resulting in higher spikelet Fertility, higher number of grains s pike(-1) and higher grain yield than either lower or higher ratios.