The Effect of Water Deficit on Yield and Yield Component Variation in Winter Wheat

The study was focused on the effect of limited water availability on yield and yield components of wheat. Soil water deficit is known to be one of the major factors limiting the productivity of cereals. Water deficit can affect plant growth and development in all stages, in early stages the rate of tiller appearance, leaf appearance and leaf area is reduced, later on the length of stems is reduced together with the number of grains per ear, and stress after anthesis shorten the duration of grain filling, thus reduces a grain size. The response of selected cultivars of winter wheat to water deficit was studied at the Field Research Station of the Mendel University, Brno, Czech Republic, in 2012/13, 2013/14, 2014/15 and 2015/16 growing seasons. A set of 26 cultivars was grown in two independent small plot experiments which were performed at two sites with different soil conditions, first site was characterised by loamy soil with good water retention and high yield potential, the second site was situated on drought prone sandy soil. Grain yield and primary yield components were determined: canopy density as the number of ears per area, and thousand grain weight as a parameter characterising grain size. The number of grains per ear was calculated using the grain yield, the number of ears per area and thousand grain weight. All yield components were statistically significantly affected by site, year and cultivar factors. Our results revealed that yield in all experiments was positively associated with high canopy density, but was not related to variations in grain weight. Under less favourable conditions association between yield and ear productivity was significant and grain weight was negatively correlated with number of ears and number of grains per ear. It suggested more severe competitiveness for resources. Four yield-based indices of drought tolerance were calculated, i.e. Stress Tolerance Index, Tolerance Index, Drought Resistance Index and Superiority Measure. Correlation analysis and principle component analysis were performed using data from both sites to show the relationships among indices and grain yield and to identify superior cultivars