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RESEARCH ARTICLE

Development of methods to overcome physiological seed dormancy of temperate annual pasture legumes to assist speed breeding

David M. Peck https://orcid.org/0000-0002-1125-7739 A * , Alan W. Humphries A and Ross A. Ballard https://orcid.org/0000-0003-0814-3586 A
+ Author Affiliations
- Author Affiliations

A South Australian Research and Development Institute (SARDI), Waite Campus, Urrbrae, SA 5064, Australia.

* Correspondence to: david.peck@sa.gov.au

Handling Editor: Brendan Cullen

Crop & Pasture Science - https://doi.org/10.1071/CP22314
Submitted: 4 April 2022  Accepted: 5 June 2023   Published online: 23 June 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing

Abstract

Context and aims: Freshly harvested seeds of temperate annual pasture legume species have physiological dormancy (PD), which delays the growth of the next generation and is thus an impediment to speed breeding. The aim of this study was to develop a method or methods of PD breaking that can achieve high germination (≥90%) within 5 days of picking freshly harvested seed.

Methods: In a series of experiments, PD breaking methods by themselves and in combination were tested on burr medic (Medicago polymorpha). The most promising methods were then tested on other annual medic species (Medicago spp.), subterranean clover (Trifolium subterraneum), and alternative species from six genera.

Key results: The successful PD breaking method involved drying pods overnight at 45°C, extracting and scarifying seed, placing seed on filter paper in a Petri dish along with non-dormant seed, imbibing seed with 4 μM benzylaminopurine, sealing the Petri dish, and incubating in the dark at 15°C. Highly dormant genotypes required the additional treatment of removing the testa.

Conclusions: We have developed an effective way of breaking seed PD in the 11 pasture legumes species from the seven genera tested. The rapid breaking of seed PD will assist speed breeding of annual pasture legumes, making it less laborious and time-bound than currently used methods.

Implications: The PD breaking methods are expected to assist basic science studies of annual pasture legume species and may be applicable to other species and genera.

Keywords: annual pasture legumes, Medicago, Ornithopus, pasture breeding, rapid generation, seed physiological dormancy, speed breeding, Trifolium.


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