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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.

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.

Seed color is a vital quality determinant of flax, significant for consumers’ acceptability, and determines the commercial values of seeds. Also, seed color as a phenotypic marker may be a convenient way to select the plants with desired traits. This study assessed a diversity panel representing 144 flax genotypes from diverse geographical origins for the existence of genetic variability for luminosity (L*) and chromaticity (a* and b*) seed color parameters, seed yield, and quality traits over two years. The genetic variance was significant for seed color parameters, demonstrating the presence of significant genetic variability, which provides a resource to objectively evaluate and select flax genotypes based on seed color according to the market demand. High heritability combined with the high genotypic coefficient of variation observed for seed yield, oil, and protein content suggested a better genetic gain upon selecting these traits. Seed yield, seed quality traits, and phenological traits showed significant negative correlation with L* and b* parameters and positive correlation with a* suggesting that the seeds’ dark background and brown color can serve as marker characters to prescreen early-flowering, high-yielding and oil and protein-rich genotypes. Interestingly 48 brown-seeded genotypes were identified as early-flowering with short height, large seeds, high thousand seed weight, and capsule diameter. In addition, 34 genotypes were characterized by light-colored yellow seeds, large seeds, late-flowering with shorter height, and high branch numbers. Our results highlighted that North America and Australia-belonged genotypes were lighter yellow-seeded than the ones from other continents. Flax genotypes from South America and Asia were high-yielding, while genotypes from North America were low-yielding genotypes. Moreover, darker brown-seeded genotypes have prevailed in the South American continent.