Control of In vitro contamination of explants from greenhouse- and field-grown trees

Summary Controlling fungal and bacterial contamination of woody plant material can be extremely difficult. Isothiazolone biocides and sodium dichloroisocyanurate have been used singly and in combination to reduce microbial contamination in bud explants derived from greenhouse- and field-grown citrus trees. Explants from greenhouse-grown trees were effectively disinfested (<5% vs. 85% contamination) using a ‘standard’ disinfestation (SD) procedure followed by culture on medium containing 5 ml l⁻¹ Plant Preservative Mixture, or by the SD procedure but substituting 300 ppm sodium dichloroisocyanurate for 48 h for the treatment with 1.05% NaOCl in the SD procedure. Disinfestation of explants from field-grown trees was less effective than explants from the greenhouse, but was improved (10% vs. 47% contamination) by using a combination of the SD procedure with 1.05% NaOCl, or 100 or 300 ppm sodium dichloroisocyanurate followed by culture onto medium containing 5 ml l⁻¹ Plant Preservative Mixture. Mention of a trademark, warranty, proprietary product, or vendor does not constitute a guarantee by the US Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.