Variability structure and heritability of germination timing in Capsella bursa-pastoris (L.) Medik (Shepherd’s purse)

Authors: DOBBS, APRIL - North Carolina State University; SOUSA-ORTEGA, CARLOS - North Carolina State University; Holland, Jim - Jim; SNYDER, LORI - North Carolina State University; LEON, RAMON - North Carolina State University

Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2023
Publication Date: 2/1/2024
Citation: Dobbs, A., Sousa-Ortega, C., Holland, J.B., Snyder, L., Leon, R. 2024. Variability structure and heritability of germination timing in Capsella bursa-pastoris (L.) Medik (Shepherd’s purse). Weed Research. 64(1):1-7. https://doi.org/10.1111/wre.12605.
DOI: https://doi.org/10.1111/wre.12605

Interpretive Summary: Weed species produce seeds that vary considerably in when they will germinate. This provides evolutionary benefit to the weed species by allowing seeds to germinate at different times, increasing the probability that some seeds will germinate at a time optimal to growth. We measured the variation and heritability among individual plants within four populations of Sheperd’s purse weed, finding significant and heritable plant to plant variation. Populations sampled from agricultural feeds had less variation than populations sampled from undisturbed habitats, presumably because agriculture imposes more regular temporal patterns of optimal growth times to the weeds.

Technical Abstract: Germination variability enables weedy species to colonise disturbed habitats and is expected to evolve in response to changing selection pressures. The paucity of information about germination variability in weeds prompted a detailed study of this topic with two agricultural and two non-agricultural populations of Capsella bursa-pastoris (Shepherd's purse). Variance in germination time was partitioned amongst and within populations, and amongst racemes and silicles within individual plant, and broad-sense heritability was estimated. Agricultural populations exhibited a shorter and more uniform germination timing than non-agricultural populations. However, differences amongst populations explained 7%–12% of the total variance, while differences amongst individuals and racemes accounted for approximately 40–54% and 10% of the total variance for germination time. For germination time, heritability'='0.4 when averaged across all time points, peaking at heritability'='0.7 at a time coinciding with the exponential phase of the germination curve. Maintaining predominantly intrapopulation variability in germination timing appears to be important for long-term fitness in this species.