Sporophytic and Gametophytic Responses of Sugarbeet to Two Pathotoxins
- H. S. Moser,
- G. A. Smith and
- S. S. Martin
In vitro toxin sensitivity has been correlated with in vivo disease resistance for several crop species but little has been reported on the association between disease resistance of the sporophyte and pathotoxin sensitivity in the gametophyte. The objectives of this research were to study the response of the gametophytic and sporophytic generations to cercosporin (CN) and cercospora beticola toxin (CBT) and to determine toxin sensitivity of sugarbeet (Beta vulgaris L.) lines with known levels of leaf spot resistance. Three sugarbeet lines having variedegrees of field resistance to Cercospora leaf spot were evaluated for sensitivity to two pathotoxins produced by the causal fungus, Cercospora beticola Sacc. The toxins, CN and CBT, were isolated and purified from cultures of the fungus, then applied singly or in varied combinations to leaf disks (sporophytic generation) or pollen (gametophytic generation). The CN CBT, separately or together, caused cellular leakage of Na and K in the sporophytic generation and potassium only in the gametophytic generation. This effect was toxin-concentration dependent, but without synergism. In the sporophytic generation, the least ion leakage response to either toxin occurred in leaf disks taken from the most disease resistant of the three lines evaluated. Gametophyticion leakage responses to the toxins also were significant, but these responses were not directly correlated with leaf disk ion leakage or with sporophytic field disease resistance. The techniques facilitated a controlled study of CN and CBT sensitivity in the sporophytic and gametophytic generations of sugarbeet.
Copyright © 1990.