Physiological Characteristics Associated with Drought Tolerance in Upland Rice of Northwest Region

The study was conducted to examine the physiological characteristics associated with drought tolerance at tillering and heading stage of several local upland rice cultivars collected from Northwest region of Vietnam. The results indicated that photosynthetic rate (CER), transpiration rate (Tr), and SPAD index (an indicator related with leaf chlorophyll content) were lower in upland cultivars than that in check variety (cv. LC93-1 ) when exposed to drought at tillering and heading stages, whereas these values were higher in upland rice at recovery stages. Drought at tillering stage significantly reduced the number of panicles per plant while drought at flowering stage significantly reduced the percentage of filled grains in the upland rice cultivars, consequently caused significant reduction in the individual grain yields. The photosynthetic rate positively correlated with transpiration rate during drought in both tillering stage and heading stage. A positive correlation was also found between the CER and SPAD index prior to drought treatment but it was not significant at drought and recovery stages. The individual grain yield was positively correlated with the CER at recovery stage. Four cultivars, Khau van lon, Nep nuong tron, Thoc gie and Te đo showed good recovery after drought treatment as well as higher individual grain yied, which might have better drought tolerance.