Post-anthesis drought stress, often associated with heat stress, is a common problem in most wheat growing regions. Previous studies have shown that elimination of leaves after anthesis can be used as a tool for simulating post-anthesis drought stress. This research used defoliation to simulate terminal drought to study its effects on grain filling rate and final grain size in wheats and correlations with physiological, morphological and agronomic characteristics. Twenty wheat and triticale genotypes, differing in height, spike length, grain size and number per spike, were defoliated 11 days after anthesis and grown with intact control plants. Both treatments were fully irrigated. Samples for grain filling rate were taken on four occasions startingat the time of leaf defoliation. At maturity the mass of 1000 grains (TGW), test weight and production per spike were determined. The reduction over all genotypes in TGW was 19.2 % (range from 10.5 to 28.2), in test weight 4.5% (range from 0.6 to 8.7) and in production per spike 13.5% (range from 1 to 27.2%). The most important determinant of grain size in defoliated plants was plant height.
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