Screening Trifolium species for susceptibility to iron-deficiency chlorosis

Abstract

Susceptible crop species may exhibit symptoms of iron (Fe)-deficiency chlorosis when grown on high pH, calcareous soils. A series of field and greenhouse experiments was conducted to determine whether differences exist among and within Trifolium species (true clovers) for resistance to Fe-deficiency chlorosis. Susceptible clover cultivars expressed chlorosis when growing in calcareous soil during periods of high soil moisture. At some field sites, irrigation was used to induce the chlorosis. 'Yuchi' and 'Meechee' arrowleaf clovers (T. vesiculosum Savi.), and 'Mt. Barker' subterranean clover (T. subterraneum L.) were very susceptible to Fe-deficiency chlorosis in the field, while 'Dixie' crimson clover (T. incarnatum L.) was moderately susceptible. 'Bigbee' berseem (T. alexandrinum L.), 'Kenstar' red (T. pratense L.), 'Kondinin' rose (T. hirtum All.), and 'Clare' subterranean clover (T. brachycalycinum Katzn. and Morley) appeared resistant to Fe-deficiency chlorosis in the field. A greenhouse screening method was also developed whereby clover seedlings were grown in calcareous soil in Cone-tainers® and Fe-deficiency chlorosis was induced by maintaining saturated soil conditions once the plants reached the fourth trifoliolate leaf stage. The screening method was tested with Yuchi arrowleaf clover and Dixie crimson clover on six Texas soils. The soils varied in available Fe (from 0.10 to 2.93 mg kg⁻¹), textural class (from coarse sand to silty clay), pH (7.1 to 7.9), calcium (1506 to 58132 mg kg⁻¹), and phosphorus (2 to 127 mg kg⁻¹). Four of the soils had a field history of inducing Fe-deficiency chlorosis in susceptible crops. The chlorosis expressed within each cultivar differed among soils, due both to soil differences and genetic variability within the plant species. Additional screening studies conducted with several cultivars of arrowleaf, crimson, and subterranean clovers indicated that genetic variation is present within each species for resistance to Fe-deficiency chlorosis, and that this variation may be manipulated to develop improved cultivars for use on high pH, calcareous soils where chlorosis is potentially a concern.