Summer dormancy improves drought survival and autumn recovery of perennial forage species in Mediterranean areas. Morocco has served as a source of germplasm for orchardgrass (Dactylis glomerata L.) breeding, but little is known of the incidence and variability of the summer dormancy trait in Moroccan orchardgrass germplasm. This paper characterizes summer dormancy and summer drought survival in Moroccan ecotypes of orchardgrass. Ten Moroccan ecotypes and the cultivar Kasbah were studied in the field in Guich experimental INRA, Rabat, Morocco. Two trials were conducted in irrigated (to test summer dormancy) and in rainfed conditions (to test drought survival after summer). Under irrigation, Moroccan ecotypes of orchardgrass and Kasbah were summer dormant. According to a summer dormancy index and a combination of physiological responses, most ecotypes and Kasbah were found completely dormant. A single ecotype was considered incompletely dormant. After intense first year summer drought, plant survival was correlated (P < 0.001) with water soluble carbohydrate (WSC) content and osmotic potential in immature leaf bases (r = 0.67 and 0.62, respectively). Two Moroccan ecotypes exhibited higher post‐drought survival after summer drought (98%) than Kasbah (90%) (P < 0.01). After a second year with severe drought, an ecotype outyielded Kasbah for autumn recovery (P < 0.001). Moroccan germplasm exhibited good levels of dormancy and agronomic performance that would be desirable in breeding programs.
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) × ‘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.
Under Mediterranean climates, the best strategy to produce rain-fed fodder crops is to develop perennial drought resistant varieties. Summer dormancy present in native germplasm has been shown to confer a high level of survival under severe drought. Nevertheless it has also been shown to be negatively correlated with annual biomass productivity. The aim of this study was to analyze the correlations between summer dormancy and annual biomass productivity related traits and to identify quantitative trait loci (QTL) for these traits in a progeny of a summer dormant cocksfoot parent (Kasbah) and a summer active parent (Medly). A total of 283 offspring and the parents were phenotyped for summer dormancy, plant growth rate (PGR) and heading date in Morocco and for maximum leaf elongation rate (LERm) in France. The individuals were genotyped with a total of 325 markers including 59 AFLP, 64 SSR, and 202 DArT markers. The offspring exhibited a large quantitative variation for all measured traits. Summer dormancy showed a negative correlation with both PGR (-0.34 p < 0.005) and LERm (-0.27 p < 0.005). However, genotypes with both a high level of summer dormancy and a high level of PGR were detected in the progeny. One genetic map per parent was built with a total length of 377 and 423 cM for Kasbah and Medly, respectively. Both different and co-localized QTL for summer dormancy and PGR were identified. These results demonstrate that it should be possible to create summer dormant cocksfoot varieties with a high annual biomass productivity.
Climate change models predict frequent and intense droughts in the world. Development of drought-tolerant species and cultivars is necessary to cope with such changes. Forage grass species are affected, especially in the Mediterranean region. The aim of the present study was to investigate the diversity for drought survival, summer dormancy, and productivity within a cocksfoot population.The study was conducted in Morocco, under field conditions from 2011 to 2013. 283 genotypes of cocksfoot and parents were tested, characterized for dry matter yield, heading date, plant height, senescence, summer dormancy, and drought survival. Results exhibited a large variability between traits. 79% of the population had survived after severe drought summer while 57% yielded more than both parents. Also, 63% of the progeny had an intermediate score of summer dormancy estimated by senescence score. Large variability was also noticed for heading date and plant height. Several accessions combined a high yield and persistence under severe summer drought. Which explain the significant correlation (r = 0.18, P < 0.005) founded between total dry matter accumulated in 2013 and plant survival. Accordingly, our results showed that we can rise persistent and resilient genotypes among population with a good level of biomass.
Cocksfoot is one of the four most important forages in the world, it is persistent and summer drought tolerant. Under Mediterranean climate, one way to produce without irrigation is to use plants resistant to drought, such as some perennial grasses as cocksfoot. The present work was conducted during 2011/2012 cropping season to evaluate some traits of progeny generated from a cross between a summer dormant genotype Kasbah cv and a summer active genotype from Medly cv under Mediterranean climate.The aim of this study was to gather hybrids pools according to common features with relation to summer dormancy. Measurements of dry matter yield, heading date, plant height, plant growth rate, senescence and summer dormancy were taken for the 229 F1 hybrids. Results showed a large variability between hybrids for all traits. 4% of hybrids were more dormant than the parent Kasbah, 35 % of hybrids yielded more than Medly, 73.8 % of progeny exceeded parents growth rate, 60 % had the greatest biovolume, more important than both parents. Significant correlations (P <0.0001) were found between all traits except heading date and senescence. Cluster analysis (CA) revealed eight groups and subgroups which showed 80 % of phenotypical similarities within hybrids and parents.
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