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RESEARCH ARTICLE (Open Access)

Flowering responses of serradella (Ornithopus spp.) and subterranean clover (Trifolium subterraneum L.) to vernalisation and photoperiod and their role in maturity type determination and flowering date stability

Laura E. Goward https://orcid.org/0000-0002-2916-1348 A B * , Rebecca E. Haling https://orcid.org/0000-0001-6743-7694 A , Rowan W. Smith https://orcid.org/0000-0002-2987-724X B , Beth Penrose https://orcid.org/0000-0001-9604-4953 C and Richard J. Simpson https://orcid.org/0000-0002-2784-7952 A
+ Author Affiliations
- Author Affiliations

A CSIRO Agriculture & Food, GPO Box 1700, Canberra, ACT 2601, Australia.

B Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 1375, Launceston, Tas. 7250, Australia.

C Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 98, Sandy Bay Campus, Hobart, Tas. 7001, Australia.

* Correspondence to: laura.goward@csiro.au

Handling Editor: Brendan Cullen

Crop & Pasture Science - https://doi.org/10.1071/CP22366
Submitted: 3 June 2022  Accepted: 24 February 2023   Published online: 6 April 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context: Serradellas (Ornithopus spp.) are promising alternative annual legumes to subterranean clover (Trifolium subterraneum L.), for permanent, temperate pastures. However, many cultivars exhibit unstable flowering dates across years. This is a risk for seed production and persistence.

Aim: This study assessed how vernalisation and photoperiod cues determine maturity type and flowering date stability among serradella cultivars.

Methods: First flower appearance was recorded for early and late maturing cultivars of yellow serradella (Ornithopus compressus L.), French serradella (Ornithopus sativus Brot.) and subterranean clover after exposure to six vernalisation treatments (0, 1, 3, 5, 7 or 9 weeks at 5°C) with subsequent growth under four photoperiods (8, 12, 16 or 20 h).

Key results: ‘Intrinsic earliness’ differed by only zero to three nodes for cultivars within species, indicating that maturity type was determined primarily by a cultivar’s responses to vernalisation and photoperiod. An interaction between these responses was observed, with a precipitous decline in the requirement for vernalisation when photoperiods exceeded 12 h. Many cultivars also displayed a persistent component to their vernalisation response, whereby long photoperiods (20 h) did not completely negate the response to vernalisation.

Conclusions: Later maturity was associated particularly with need for long exposure to the vernalisation treatment to minimise the duration from sowing to first flower appearance. Stable flowering is more likely when a cultivar has components of its vernalisation requirement that are not satisfied before autumn ends to prevent premature flowering, and a photoperiod response in spring that overrides any unmet vernalisation requirement.

Implications: Persistence by serradella cultivars requires selection for suitable responsiveness to vernalisation and photoperiod.

Keywords: adaptation, annual legumes, daylength, Mediterranean, pasture, persistence, phenology, temperate.


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