This study was conducted to evaluate drought tolerance and persistence in a germplasm of smooth bromegrass and association of forage productivity with different traits. Thirty‐six genotypes of smooth bromegrass were clonally propagated and evaluated under two soil moisture environments for three years (2013–2015). High genotypic variation was observed among genotypes for all the measured traits. Drought stress decreased mean values for traits related to productivity. Also, the long‐term stress for three years reduced the persistence of plants. Results indicated that indirect selection based on components of forage yield, which had high heritability and high correlation with yield, would be more effective to improve drought tolerance in this germplasm. The results of principal component analysis showed that there was a negative relationship between phenological traits with the persistence‐related traits and yield production. This suggests that selection for earliness may indirectly promote persistent genotypes. The results showed that some Hungarian genotypes are valuable gene sources for persistence. The most persistent genotypes from both groups (Iranian and foreign) were identified using the biplot method. These genotypes may be useful for the development of populations for future studies.
The genetic basis of physiological responses to drought and its association with productivity, persistence and summer dormancy is not clear in orchardgrass (Dactylis glomerata L.). Thirty-six orchardgrass genotypes were evaluated under water stress and non-stressed conditions during 2 years (2013–14). High genotypic variation was observed for all of the agronomic and physiological traits. Water stress reduced dry matter yield, relative water content and chlorophyll content while significantly increasing carotenoids, water-soluble carbohydrates, proline and chlorophyll a : b ratio. The results indicated that carotenoids and proline accumulation could not be used for discriminating drought-tolerant genotypes of orchardgrass, whereas water-soluble carbohydrates may be used to achieve this purpose. Moreover, the results showed that the stable genotypes that have lower changes in productivity from normal to water-stress environments also have more persistence. No association was found between summer dormancy and drought tolerance measured by both physiological and yield-based drought-tolerance indices. Some of the drought-tolerant genotypes had relatively high persistence and better autumn recovery, a characteristic useful for the development of new synthetic varieties.
Polycross designs bridge the two usual mapping approaches (bi-parental mapping and association analysis) and increase mapping power by incorporating greater genetic diversity. In this study, we used diverse genotypes selected from polycrossed progenies to identify marker loci associated with a set of seed- and forage-related traits as well as drought tolerance in orchardgrass (Dactylis glomerata L.). Associations were estimated between phenotypic traits and 923 DNA markers (including 446 inter-simple sequence repeats and 477 sequence-related amplified polymorphism markers). Positive relationship was found between forage yield and seed yield under normal and water-stress conditions, indicating that simultaneous improvement of seed and forage yield could be achieved in orchardgrass. The results of population structure analysis identified five main subpopulations possessing significant genetic differences. Under normal and water-stress conditions, respectively, 341 and 359 markers were significantly associated with the studied traits. Most of these markers were associated with more than one trait. Water-environment specificity of trait-associated markers indicates that genotype × environment interactions influence association analysis. However, 75 stable associations were identified across two moisture conditions for traits such as seed and forage yield. Marker–trait association revealed that markers M1/E1-5, M2/E6-5, M3/E4-6, P14-7 and P845-7 were consistently linked with drought-tolerance index. The identified marker alleles associated with multiple traits across environments may be considered for further analysis for their chromosome locations, the corresponding sequences and their potential functions.
In smooth bromegrass (Bromus inermis Leyss), few efforts have been made to develop rapid and reliable physiological indices for selection of persistent and drought‐tolerant genotypes. In addition, the association of these indices with seasonal growth activity, such as summer dormancy and autumn recovery, has not been studied. In this research, 36 genotypes of smooth bromegrass were clonally propagated and evaluated under water stress and nonstress conditions during 2013 to 2014. Water stress greatly influenced physiological functions and persistence, which affect plant growth and biomass production. Among the 36 randomly selected genotypes from the progeny of 25 half‐sib polycross families of smooth bromegrass, high genotypic variation was observed for all measured traits. Leaf proline content was not correlated with drought tolerance and persistence. However, carotenoid content and water‐soluble carbohydrates were correlated with drought tolerance and can be suggested for indirect selection of drought‐tolerant genotypes. Three genotypes (G8IHA, G13HUN, and 32HUN) were found to be more drought tolerant than others based on stress tolerance index, higher dry matter yield, summer dormancy, and relatively higher persistence and autumn recovery.
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