Study of drought stress effects in different growth stages on potato cultivars*

In order to study effects of drought stress at different growth stages in potato, three cultivars: Marfona, Agria and Draga were planted in 20 lit. pots-using a completely randomized design (CRD) with five replications. Three levels of drought stress (40%, 60%, 80% of soil available water=SAW) and a control (100% SAW) were applied in three growth stages (Planting to emergence, emergence to stolon initiation and stolon initiation to tuber initiation) and were arranged in factorial combination together with potato cultivars. Results showed that drought stress decreased relative water content (RWC), water use efficiency (WUE), Tuber no./plant, dry matter percent (DM%) and tuber yield, but increased leakage from cell wall. Agria demonstrated the highest tuber yield and WUE but the lowest leakage from cell wall. However, Draga had the lowest tuber yield, RWC and Tuber no./plant, but the highest DM%. Drought stress at stolon initiation stage decreased tuber yield. Drought stress levels of 60% SAW severely affected the tuber yield, however the difference between 40% and 80% SAW was not significant. Differences of drought stress levels were significant only for Agria. The result indicated that high RWC together with medium Tuber no./plant led to optimum assimilate partitioning among tubers, hence higher tuber yield.