Maturity type and flowering date instability among serradella (Ornithopus spp.) cultivars

Abstract

Grass-legume pastures on acid soils of the temperate/Mediterranean climatic zone (∼29 million ha) of southern Australia are based almost entirely on a single annual legume (subterranean clover; Trifolium subterraneum L.). Serradellas (Ornithopus spp.) are options for legume diversification. We assessed maturity type among current serradella cultivars to evaluate whether widespread use is possible. Cultivars of yellow (Ornithopus compressus L.), French (Ornithopus sativus Brot.), and slender serradella [Ornithopus pinnatus (Mill.) Druce], and five subterranean clover control cultivars were sown at four sites in late autumn 2017, and in early and late autumn 2018. We determined the date at which 50% of the plants representing each cultivar had produced their first flower. Maturity type (e.g., early-season, mid-season, and late-season) was determined by comparison with the clover controls. Serradella cultivars ranked consistently by median flowering date within sites in both years, but the maturity type of several cultivars differed between sites. Gaps in the maturity range of serradellas needed for southern Australia included very-late maturing yellow serradellas, and very-early, late, and very-late hardseeded French serradellas. Unlike the clovers, many serradellas did not flower at the same time in spring when sown at different times in autumn. This was of similar concern to gaps in the maturity-type range because unstable flowering confounded maturity type classification. We argue that unstable flowering dates may also adversely impact forage quality, seed production and legume persistence. New serradella cultivars should exhibit stable flowering dates to support their adaptation in grasslands where the commencement of autumn rainfall is highly variable.