Summer dormancy in orchardgrass: evaluation and characterization through ecophysiological and genetic studies
Climatic change manifested by increasing summer drought necessitates the development of drought-tolerant forage grass cultivars. Summer dormancy is a major trait conferring drought survival and autumn recovery of perennial grasses in Mediterranean areas. Moroccan ecotypes of orchardgrass (Dactylis glomerata L.) expressed 67% greater degree of summer dormancy than tested cultivars except the highly dormant ‘Kasbah.’ Furthermore, summer dormancy was highly correlated with perenniality (r = 0.63, P < 0.01). However, summer dormancy was associated with low productivity. A breeding program was started to develop productive orchardgrass cultivars with high summer dormancy. Hybrids between high- and low-dormancy cultivars produced offspring with combinations of enhanced dormancy and biomass production indicating potential for breaking the negative dormancy-yield association. For example, Kasbah (dormant) x ‘Medly’ (summer-active) hybrids were 57% more dormant than Medly and 32% higher yielding than Kasbah. Genetic analysis of heritability and molecular markers will provide more information on the genetic control of summer dormancy. Results of crosses between contrasting populations of orchardgrass indicate potential for combining the desirable traits of summer dormancy and high annual herbage yield into an eventual cultivar.