Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/5/2008
Publication Date: 12/15/2009
Citation: Vick, B.A., Cook, L.W., Jan, C.C. 2009. Characterization of a Green Non-Dormant Sunflower (Helianthus annuus) Mutant NDG. Plant Breeding. 128:645-650. Interpretive Summary: Occasionally during a breeding program, an unusual plant appears as the result of an unexpected mutation. This was the case when we noticed a sunflower plant in which the head was drying down for seed collection. But rather than dry down, the seeds on the head started to germinate and grow. We called this mutant "ndg" (nondormant green). This was a plant that had been derived from several sources through multiple crosses. One of the parents in the background of this plant was HA 89, a common cultivated line used as a standard reference sunflower line. Seeds of the mutant sunflower line frequently germinate on the head about 40 days after pollination. In contrast to other nondormant sunflower mutants reported previously, the cotyledons of this mutant remain green, whereas other nondormant mutants exhibit loss of pigmentation. The objective of our investigation was to compare levels of abscisic acid (ABA), a plant hormone that induces dormancy in developing embryos, in the "ndg" mutant with abscisic acid levels in normal type HA 89 from which "ndg" was derived. Measurements by immunoassay showed that abscisic acid content in the mutant and normal type were the same, indicating that reduced abscisic acid was not the cause of nondormancy. Furthermore, treatment of "ndg" mutant embryos with abscisic acid failed to prevent germination, suggesting that this mutant differs from normal sunflower by an insensitivity to abscisic acid that results in a failure to induce dormancy.
Technical Abstract: A sunflower (Helianthus annuus L.) mutant was observed in the progeny of a cross between the sunflower cultivar HA 89 and an amphiploid of a H. divaricatus L. x P21 cross that exhibited loss of dormancy induction in the developing embryo. Seeds of this mutant frequently germinate on the head about 40 d after pollination (DAP). The cotyledons of this mutant remain green, whereas some other nondormant mutants exhibit loss of pigmentation. The objectives of this investigation were to compare levels and activities of abscisic acid, a plant hormone that induces dormancy in developing embryos, in the nondormant green mutant (ndg) and HA 89 from which ndg was derived. Immunoassays showed that abscisic acid was present in ndg and the levels were not significantly different from those in HA 89. Exposure of excised ndg mutant embryos to 40 uM abscisic acid failed to prevent germination, suggesting that nondormancy could result from an impairment in ABA receptors or from a defect in other proteins participating in the subsequent signaling pathway that normally induces dormancy.