Greenhouse Evaluation of Subterranean Clover Species for Susceptibility to Iron‐Defeciency Chlorosis

Abstract

Subterranean clover (subclover) is the common name for three Trifolium species (T. brachycalycinum Katzn. and Morley, T. yahninicum Katzn. and Morley, and T. subterraneum L.), which show promise for use in winter pastures in the southeastern USA. On calcareous soils in Texas, ‘Mt. Barker’ subciover (T. subterraneum) often has Fe‐deficiency chlorosis, while ‘Clare’ subclover (T. brachycalycinum) appears to be resistant. Our objective was to screen 22 available subclover cultivars in the greenhouse for susceptibility to Fe‐deficiency chlorosis. Three replications of seven plants per cultivar were grown in Conetainers ® in two calcareous soils. At 4 wk of age, the plants were subjected to high soil moisture conditions to induce the chiorosis. Two weeks later, all plants were scored and leaf samples were analyzed for total chlorophyll content. Both parameters indicated a large difference among cultivars for susceptibility to Fe‐deficiency chlorosis. Visual chiorosis scores and leaf chlorophyll contents were inversely related (r2 = 0.69). Cultivars belonging to T. brachycalycinum had no chlorosis and had high leaf chlorophyll contents (> 1.2 mg g−1). Within the species T. yanninicum, three cultivars appeared to be only slightly susceptible, while ‘Yarloop’ had moderate chlorosis when grown in the Partita soil (Clayey, mixed, hyperthermic, shallow Petrocalcic Paleustoil). Cultivars of the species T. subterraneum had the greatest range of chlorosis scores. ‘Karridale’ was consistently most susceptible to Fedeficiency chlorosis, while ‘Woogenellup’ was the least susceptible. The variation among cultivars within the species T. subterraneum suggests that selection for resistance to Fe‐deficiency chlorosis maybe possible within this species.