VARIATION IN DURATION OF PREANTHESIS PHASES OF DEVELOPMENT IN BARLEY (HORDEUM-VULGARE)

The first of 2 studies reported in this paper investigated the variati on in 15 barley genotypes for the durations of 3 periods of pre-anthes is development [leaf initiation (LI), spikelet initiation (SI) and spi kelet growth (SG) phases], and the degree of independence of the durat ion of the SG phase from each of the LI and SI phases. There were diff erences between genotypes in the duration of the SI and SG phases whic h were not closely correlated (r=-0.58, P <0.05) across genotypes, ind icating the feasibility of genetically combining different durations o f the 2 phases while maintaining a constant time to anthesis. The dura tion of the LI phase was closely correlated with time to anthesis (r=0 .82, P <0.001) but not with the duration of either the SI or SG phase. The rate and duration of spikelet initiation were negatively correlat ed across genotypes (r=-0.75, P <0.01). There was little variation in the number of spikelet primordia formed over the range of genotypes bu t there was considerable variation in the number of aborted spikelet p rimordia. The study indicated the likelihood that in breeding to incre ase the yield potential of the spike in barley, there is more potentia l for reducing the level of spikelet primordia abortion during the SG phase than increasing the number of spikelet primordia per spike. The second study investigated whether 3 photoperiod regimes (15.5, 14, and 12-13 h), imposed for the duration of the LI and SI phase, had any su bsequent effect on the duration of the SG phase in 2 cultivars, Bandul la and Galleon. There were no major effects, suggesting that the durat ion of the SG phase was largely independent of the duration of the 2 p revious phases.