Suppression of Septoria tritici by foliar applied potassium chloride on winter wheat.
The effect of foliar applied potassium chloride on Septoria tritici on winter wheat was
quantified and possible modes of action investigated by in vitro, glasshouse, controlled
environment and field experiments between 1996 and 1999. In vitro experiments showed
that as the concentration of potassium chloride increased, mycelial growth and
germination of conidia decreased (EO sos of 1.36M and 0.7M, respectively). One
glasshouse and two field experiments showed a significant reduction in the leaf area
affected by S. trttict after foliar application of potassium chloride compared to untreated
controls. In general, application of potassium chloride reduced the leaf area affected by
S. tritici by 20 -.40%. However, a significant yield increase was not observed.
Potassium chloride applied to the lower leaves of winter wheat did not confer systemic
acquired resistance against S. tritici on the upper leaves. Inhibition of conidial
germination, on leaf surfaces by potassium chloride was observed. Similar inhibition was
observed when polyethylene glycol, an inert osmoticum, was applied at the same
calculated osmotic potential. During field experiments there was no significant difference
in the leaf area affected by S. tritici in plots treated with potassium chloride or
polyethylene glycol, although both significantly reduced the leaf area affected compared
to untreated control plots. Therefore, the principal mode of action of potassium chloride
was proposed to be as a result of adverse osmotic conditions caused by the salt on leaf
surfaces. However, the addition of a range of adjuvants to potassium chloride did not
increase the efficacy of S. tritici control in glasshouse studies.
The results from this study show that potassium chloride, when applied to foliage of
winter wheat can reduce the leaf area affected by S. tritici and it is proposed that this
reduction was by adverse osmotic conditions caused by the salt on leaf surfaces.