VARIABILITY OF SUNFLOWER INBRED LINES TO IRON-DEFICIENCY STRESS

Sunflower (Helianthus annuus L.) has been classified as a 'Fe-efficient' species; however differences have been reported in susceptibility to 'Fe deficiency stress' among cultivars and inbred lines. This paper reports research on responses of inbred lines to 'Fe deficiency stress' (release of protons and root capacity to reduce Fe). When plants were grown individually in aerated nutrient solution without Fe the new selected inbred lines were classified as: a) Lines with good 'Fe deficiency stress' response (RHA 271, RHA 273 and RHA 274); b) Lines that did not lower root external pH (HA 89 and RHA 299), one with very low reducing capacity (HA 89) and the other with reducing capacity (RHA 299); and c) One segregating line (RHA 276) from which two sister lines were selected. When a buffer (5 mM MES, 2-(N-morpholino) ethanesulfonic acid) was added to the root nutrient solution without Fe during growth the reducing capacity of 'Fe-inefficient' lines was higher for buffered than for unbuffered roots. Therefore, differences among lines for reducing capacity depend on experimental conditions.