Genetic and Physiological Aspects of Drought Tolerance in Smooth Bromegrass

The genetic basis of physiological traits and their association with forage yield and drought tolerance is poorly understood in smooth bromegrass (Bromus inermis Leyss). In this study, half-sib families from a polycross population were evaluated in the field under normal and water deficit conditions during 2012 and 2013. Water deficit greatly influenced physiological traits and forage production. Under water deficit conditions, most of physiological traits decreased, whereas carotenoid content, proline content, and ratio of chlorophyll a/chlorophyll b increased. Moderate to high estimates of heritability and genetic variation for yield and physiological traits indicated that selection in this germplasm would be useful in achieving genetic progress. Heritability estimates were slightly decreased for agromorphological traits under water deficit conditions, but the heritability of physiological traits increased in response to water deficit conditions. Significant associations between drought tolerance index and chlorophyll a, chlorophyll b, total chlorophyll content, carotenoids, and proline content showed the importance of these traits to confer drought tolerance in smooth bromegrass. Several genotypes with relatively higher tolerance and forage yield were identified under both moisture regimes that can be used in further breeding programs of smooth bromegrass.