The effect of a common date of either anthesis or planting on the rate of development and grain yield of wheat

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Abstract
In field experiments in southern Queensland comparisons were made, for a given wheat genotype, of the influence on grain yield of varying the rate of development while maintaining common dates either of anthesis or of planting. Rates of development were varied by the use of extended photoperiods or of isogenic lines of Triple Dirk varying in developmental rate. Hastened development lowered spikelet numbers and total dry weight at anthesis in all the genotypes tested, under highly stressed dryland and fully irrigated conditions. The saving in water use due to fast development rate, measured as available water at anthesis, was not proportional to the difference in total dry weight. This could be due to additional effective rainfall in the longer growing season wheats, to a high rainfall event just prior to anthesis reducing differences in available soil water, or to the complete use of soil water reserves in all treatments. With a common anthesis date, the saving in water use by the quicker developing crops (i.e. later planted) did not offset their lower dry weights and spikelet numbers at anthesis, so that there was either no yield difference or a yield decline with faster development rates. Where common dates of planting were compared the faster developing treatment (i.e. earlier flowering) still showed a trend to reduction in grain number per unit area, but this was usually offset by higher kernel weights. The yield outcome in this case was dominated by the prevailing environmental conditions at the differing anthesis dates.