Abstract:

In this study, the superior dryland and the irrigated varieties were analyzed in term of population yield performance in field under rain−fed and supplemental irrigation conditions, biomass accumulation and physiological features during drought stress, aimed at instruction for genetically improving drought resistance of irrigated varieties. Superior dryland variety Jinmai 47 and superior irrigated variety Shijiazhuang 8 were selected as testing materials. Field population experiment was carried out in three consecutive growing years under two water treatments of rain−fed and supplemental irrigation conditions to compare their yield performance in field. Pot cultivation experiment protected by rain−out shelter was also carried out, with wheat plants subjected to drought stress at jointing stage. Individual plant biomass variation during the period of drought stress and individual plant grain yield after harvest were investigated, and net photosynthetic rate, stomatal regulation, osmotic regulation, and membrane stability regulation, as well as antioxidant system were also determined with stress aggravating. The results showed that: (1) Jinmai 47 obtained higher yield than Shijiazhuang 8 under rain−fed condition, and corresponded to Shijiazhuang 8 in most cases under supplemental irrigation condition, except suffering yield loss due to lodging in wet years. (2) Jinmai 47 accumulated lower biomass during 20d of drought stress than Shijiazhuang 8, while gained higher grain yield than Shijiazhuang 8. The net photosynthetic rate was lower on the 8^th day of stress, but higher after re−watering 3d in Jinmai 47 than in Shijiazhuang 8, indicating the stronger restoring ability of Jinmai 47. (3) Measurements on the 5^th, 10^th and 15^th day of stress showed that stomatal conductance and osmotic potential in the two varieties decreased, but no significant difference between the two varieties. Measurement on the 15^th day of stress showed the membrane ion leakage increased in the two varieties, with the increase magnitude being rather larger in Shijiazhuang 8 than in Jinmai 47, indicating the higher membrane stability in Jinmai 47. (4) The two varieties both enhanced the activity of antioxidant enzymes SOD, POD and CAT under drought stress, but only SOD activity was significantly higher in Jinmai 47 than in Shijiazhuang 8, with no significant difference in POD and CAT activities between the two varieties, indicating that SOD plays an important role in regulating membrane stability of Jinmai 47. In conclusion, under long−last severe drought stress, the superior dryland variety Jinmai 47 reduced photosynthetic rate, while increased antioxidant capacity to maintain cellular membrane stability and obtained higher recovering ability after released from stress. As a result, although the variety accumulated smaller biomass during drought stress at jointing stage, it gained higher grain yield at final harvest, thus demonstrating stronger drought resistance.

Key words: Winter wheat, Dryland variety, Irrigated variety, Yield, Drought resistance