ARS | Publication request: Trichoderma rot on ‘Fallglo’ Tangerine Fruit

Submitted to: Florida State Horticultural Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 11, 2011
Publication Date: N/A

Technical Abstract: In September 2009, Trichoderma rot symptoms were observed on ‘Fallglo’ fruit after 7 weeks of storage. Fourteen days prior to harvest, fruit were treated by dipping into one of four different fungicide solutions. Control fruit were dipped in tap water. After harvest, the fruit were degreening with 5 ppm ethylene for 5 days. Decaying fruit were collected from the control treatment, which had an average of 2.6% decay. The decay area became brown and leathery and was round to elliptical in shape with an average diameter of 4 to 6 cm. A fungus was isolated from the diseased peel of symptomatic fruit. The fungus grew rapidly on potato dextrose agar (PDA) medium and produced white mycelium after one day on PDA at 25°C and filled the Petri dish (100 X 15 mm) after 5 days. The colony turned white to grey after 14 days with scattered green tufts. Green conidia were formed in concentric rings and first observed on PDA at 25°C within 72 hours. Conidiophores were branched with flask-shaped phialides. The fungus was identified as a Trichoderma sp. based on the morphology, which was confirmed by sequencing of the internal transcribed spacer regions and portions of the gene encoding translocation elongation factor 1-alpha. Speciation utilizing TRICHOBLAST is currently underway. ‘Fallglo’ fruit developed the same symptoms that were previously observed 4 days after wound-inoculated with a spore suspension (2.1 X107/ml). Fruit dipped in Switch, Topsin-M, HDH Peroxy, and Bravo had 0.0% incidence of decay.