The effect of nitrogen source on in vitro growth of Neonectria ditissima (European canker)
Nitrogen fertilisers are widely used in apple orchards. However, the effects of various nitrogen sources on growth and sporulation of the fungus Neonectria ditissima, which causes European canker, are not fully understood. The effects of various nitrogen sources commonly used in apple orchards (potassium nitrate, ammonium chloride, ammonium nitrate, ammonium sulphate, Nitrophoska® and urea) on percent germination and germtube growth of N. ditissima conidia were tested in vitro. Nitrogen concentrations below 0.2 mol/L did not significantly affect percent conidial germination; however, concentrations above 0.2 mol/L significantly decreased germination. Germtube growth was also affected, generally decreasing with increased N. Percent germination was influenced by the N source, but germtube growth was not. Very low concentrations of urea were indicated to stimulate germtube growth. Higher concentrations, showed toxic effects on both germination and germtube growth. The presence of exogenous N from various sources did not affect initial germination and growth in the N. ditissima infection process of apple tissues.
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