Genetic and Environmental Effects on Seed Weight and Seed Yield in Switchgrass
A positive correlation exists between seed weight and seedling vigor. The objective of this study was to determine genetic and environmental effects on seed weight and seed yield within two switchgrass (Panicum virgatum L.) cultivars. Thirty half-sib families of ‘Sunburst’ (large seeded) and ‘Summer’ (small seeded) were evaluated for 3 yr in Kentucky bluegrass (Poa pratensis L.) sod (competitive) and tilled (noncompetitive) spaced-plant nurseries at Brookings, SD, and in a tilled spaced-plant nursery at Highmore, SD. Parents were evaluated in a separate nursery. Significant differences were found among families within both cultivars for 100-seed weight, but significant family × environment interactions indicated nonuniformity in responses of families to environmental variability. Narrow-sense heritability estimates for 100-seed weight were 0.88 for Sunburst and 0.58 for Summer. Seed weight increased in response to increased ambient moisture, but was similar for competitive and noncompetitive environments (grand means were 101 and 175 mg 100 seeds−1 for Summer and Sunburst, respectively) at Brookings. However, mean plasticity for seed weight was evident from markedly reduced seed weights for both cultivars at Highmore. Magnitude and direction of plasticity for seed weight differed for the two cultivars. Plastic families of Summer generally had heavier seeds in the competitive environment, whereas those of Sunburst had heavier seeds in the noncompetitive environment. Significant differences were found among families within both cultivars for seed yield. Summer had 70% higher mean seed yields than Sunburst, and annual seed-yield means varied by greater than 80%. Seed weight was highly responsive to temporal and spatial environmental variation, but genetic variation was adequate to expect progress from selection within both cultivars.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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