Variation in duration of pre-anthesis phases of development in barley (Hordeum vulgare)

The first of 2 studies reported in this paper investigated the variation in 15 barley genotypes for the durations of 3 periods of pre-anthesis development [leaf initiation (LI), spikelet initiation (SI) and spikelet growth (SG) phases], and the degree of independence of the duration of the SG phase from each of the LI and SI phases. There were differences between genotypes in the duration of the SI and SG phases which were not closely correlated (r=-0.58, P <0.05) across genotypes, indicating the feasibility of genetically combining different durations of the 2 phases while maintaining a constant time to anthesis. The duration 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 correlated across genotypes (r=-0.75, P <0.01). There was little variation in the number of spikelet primordia formed over the range of genotypes but there was considerable variation in the number of aborted spikelet primordia. The study indicated the likelihood that in breeding to increase the yield potential of the spike in barley, there is more potential 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 subsequent effect on the duration of the SG phase in 2 cultivars, Bandulla and Galleon. There were no major effects, suggesting that the duration of the SG phase was largely independent of the duration of the 2 previous phases.