اثر تنش خشكي برعملكرد و كارآيي مصرف نور درارقام كلزا (.Brassica napus L)

Effects of drought stress on radiation use efficiency and yield of winter Canola (Brassica napus L.)

A two years field experiment was conducted during 2005 and 2006 growing seasons in the Agriculture Research Station of Torogh, Mashhad to evaluate response of Canola cultivars to limited water. Experimental design was a split plot with three replications in which irrigation regimes were allocated to main plots and cultivars to subplots. Irrigation treatments including 100 (Rl), 80 (R2), 65 (R3) and 50 (R4) percent of water requirement based on previously determined water requirement of Canola in Mashhad. Cultivars were Zarfam, Okapi, SLM046 and Licord. The results showed that yield and yield components were significantly affected by drought stress in two years. In R3 seed yield was decreased at first year however, at R4 decreased seed yield was observed in both years. The highest radiation use efficiency (RUE) for Zarfam, Okapi, SLM046 and Licord was obtained at Rl, R4, R4 and R3, respectively. This difference was partly due to decreased leaf area index (LAI) with decreasing irrigation levels. The highest and lowest LAI was observed at control (Rl) and severe stress (R4), respectively. Harvest index (HI) was affected by drought stress only in R4 treatment. These results showed considerable differences between cultivars in respect to LAI, RUE and HI under drought stress. The lowest and highest RUE of 0.95 and 2.6 g DM MJ-1 were obtained in drought stress treatments. It can be concluded that in this experiment drought resistance in Canola cultivars depends on their higher LAI and RUE.