Yield stability and development in two- and six-rowed winter barleys under Mediterranean conditions

Abstract

Under the irregular weather that characterises Mediterranean environments, to increase yield stability in cereal crops represents an important objective for agricultural progress. In this study, a series of field experiments were conducted with two- and six-rowed barley cultivars under Mediterranean conditions (southern Spain) to determine their differences in yield stability and to identify the influence that initiation and mortality of both the spikelet and tiller could exert on yield differences. Yield stability differed markedly in two- and six-rowed cultivars. The yield of two-rowed cultivars was more responsive to environmental changes than that of the six-rowed cultivars, which consistently showed more stable behaviour, outyielding the two-rowed barleys in the lowest yielding environments. Two-rowed cultivars had far more spikes per m 2 than did six-rowed cultivars, while the latter consistently had more grains per spike, with a lower average grain weight. Yield differences among environments, for both groups of cultivars, were more associated with changes in number of grains per unit of land area than to differences in individual grain weight. Six-rowed cultivars, as expected, produced virtually threefold more spikelets per spike than the two-rowed cultivars. Although there was a large difference between two- and six-rowed cultivars in spikelet abortion, the proportion of abortion was fairly stable across environments. Two-rowed cultivars consistently tillered at a higher rate (0.11 tillers per day) than the six-rowed barleys (0.07 tillers per day), though the magnitude of the difference in tillering was more affected by the environment than was the difference in spikelet initiation. Under Mediterranean conditions the constitutive capacity of six-rowed cultivars to have a reduced tillering rate, even under favourable growing conditions, as compared with that of two-rowed cultivars could be a useful strategy to save resources that may be more efficiently used during the critical phases for yield determination. This explains their higher yield stability when compared with two-rowed cultivars.