Changes in winter wheat grain yield and quality after simulated intensive pre-harvest rainfall

The authors in pot experiments verified the effect of simulated intensive pre-harvest rainfall (50-70 mm for 8, 10 days respectively) on the yield and technological quality of the grain of winter wheat variety Astella in the years 2003 and 2005. In this experiment the pots with diameter of 20 cm were used. The pots were filled with the mixture of soil (5 kg), silicate sand (1 kg), and nutrients. Into the each pot 20 seeds were sown and singled to ten plants in spring. In the phase of milk ripeness the pots were put into the three following blocks: A - the plants were watered at need (after weighting the pots) every second day up to 65% of full water capacity (FWC). The plants were exposed to simulated rainfall (manual garden sprinkler) the following ten and eight days (in 2003 and 2005 respectively), when they received 70 and 50 mm of moisture respectively. B - in the same period the plants were put under the awning (prevention of atmospheric rainfall) and according to necessity watered up to 50% of FWC every second day. After 14 days the blocks of pots were displaced -the plants of A block were put under the awning and watered to 50% of FWC, B block plants were watered to 65% of FWC and exposed to simulated rainfall, when received 50 mm of moisture. C - the control variant, the plants were not treated with simulated rainfall (the pots were continually under the awning), but were watered to 65% of FWC, whereby the optimal variant with a good soil moisture was simulated. Each block had 9 and/ or 7 pots - four of them were used for determination of the yield, yield-forming elements, and grain technological quality (SDS-test, wet gluten, falling number), the next six pots (three in 2004) for ears sampling, grain separation, and the following analysis of antioxidant enzyme superoxid-dismutase. Intensive pre-harvest rainfall simulated in the phase between the milk and wax grain ripeness (DC 73-75) insignificantly decreased the yield as compared to C variant. Drought stress (water deficiency) decreased significantly even highly significantly (an average by 34%) the grain yield mainly as the consequence of reduction of grain number per ear. From the point of yield quality, intensive rainfall between the milk and wax ripeness dramatically decreased the wet gluten content in grain, less expressively falling number value (the falling number drop increased α-amylase activity). In wet conditions elastic-viscous properties of the flour (SDS-test) worsened, while in drought conditions in the same growing phase, the higher SDS-test values in comparison with C control were obtained. Intensive rainfall in the phase between the milk and wax grain ripeness more expressively influenced all analyzed parameters of grain yield than the later rainfall between wax and technological grain ripeness. Pre-harvest rainfall in the stage from the milk to wax ripeness manifested a relatively lower effect on su-peroxiddismutase activity changes in the grain than its absence. It confirms a significant function of this anti-oxidant enzyme in a defensive strategy of winter wheat plants against waterlogging and more significantly against the consequence of a long-time drought stress. This article was supported by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences during the work on project no. 1/0596/03 Reduction of negative environmental conditions influence on winter wheat yield and grain quality.