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Drought Response of Winter Wheat Cultivars Grown under Field Stress Conditions¹

Ten winter wheat cultivars (Triticum aestivum L.) were evaluated for grain yield and yield components under moisture stress conditions at three locations. Osmotic potential (_n.) was determined from leaf samples taken during the early part of grain filling. Consistent genetic differences were found for _n... Significant positive associations of _n with yield existed at two locations (r= 0.49 and 0.45). Path-coefficient analysis indicated that _n. contributed positively to yield differences primarily by way of kernel weight at Pendleton, the least stressed site. Increased _n made contributions to high yield via spikelets/spike, kernels/spikelet, and kernel weight at Pilot Rock, a severely stressed site. High spike numbers had a tendency to be associated with low plant water status (low _n). At Heppner, the large direct effect on yield by spikes/m² negated the small positive indirect effects of _n via the later-developed yield components. In a growth analysis study at Pilot Rock, five cultivars were sampled over four time intervals from spike initiation to ripe stage. The mean _n decreased over time (- 17.1 to - 31.8 bars). Cultivar _n values ranked consistently and differences became larger after the onset of high soil moisture stress (< - 15 bars).

The drought-resistant cultivar ‘Yamhill’ avoided drought stress by maintaining a high plant water status during reproductive development. The high growth rates during heading and anthesis and a high kernel weight indicated that this cultivar was less affected by high external water stress. The drought-resistant cultivar ‘Wanser’ tolerated a high internal stress by maintaining a large number of tillers through development to harvest. Characterization of other cultivars also indicated that both avoidance and tolerance traits contributed to grain yield under drought stress.

Key Words: Triticum aestivum L. • Drought resistance • Drought avoidance • Drought tolerance • Growtha analysis, Osmotic potential

² Former research assistant (now assistant professor, Plant Science Dep., South Dakota Univ., Brookings SD) and professor, Crop Science Dep. Oregon State Univ. Corvallis, OR.

Received for publication December 3, 1979.

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