COMPARISON OF PHYSIOLOGICAL METHODS TO ASSESS DROUGHT TOLERANCE IN OATS

Several methods have been developed to assess differences in cultivar response to drought. This study consisted of 19 oat (Avena sativa L.) cultivars and breeding lines and three species of wild oats, and focused on comparison of several physiological screening methods - CO2 exchange rate (CER), stomatal conductance, stomatal resistance, disparity between air and leaf temperatures, accumulation of abscisic acid (ABA) and proline, and relative water content (RWC) - with yield losses. Early drought, occurring at four-five leaf stage or close to pollination date resulted in significantly reduced above-ground vegetative biomass and panicle weight. Reductions in panicle weight due to drought were greater than those in vegetative phytomass, which resulted in decreased harvest index (HI). Drought stress significantly increased stomatal resistance and accumulation of ABA and proline, whereas stomatal conductance, disparity between air and leaf temperatures and RWC, decreased owing to water deficit. Comparison of screening methods by calculating drought tolerance indices showed that none of the indices was associated with degree of yield losses. However, photosynthetic characters correlated with RWC both at early growth stages and close to pollination. Therefore, further studies that profoundly evaluate the relationship between these screening methods and degree of yield losses are needed.