Antimicrobial effect of rhizome and medicinal herb extract in controlling postharvest anthracnose of dragon fruit and their possible phytotoxicity

A study was conducted to evaluate the antifungal effect of ginger, turmeric rhizome and dukung anak (medicinal herb) crude extract against Colletotrichum gloeosporioides (Penz.) Penz. & Sacc.at minimal concentrations 2.5 g L-1 , 5.0 g L-1 , 7.5 g L-1 and 10.0 g L-1 (in vitro). Additionally, the possibility of using these extracts as an edible coating to control postharvest anthracnose in dragon fruits at maximum concentrations of 5.0 g L-1 , 10.0 g L-1 and 15.0 g L-1 (in vivo) were elucidated. The results showed that all plant extracts possessed significant antifungal activity against C. gloeosporioides by inhibiting mycelial growth and conidial germination , and caused distortion, shrinking and swelling of fungal hyphae. Ginger crude extracts at 10.0 g L-1 showed the best effect in vitro by suppressing mycelial growth (88.48 %) and conidial germination (87.50 %) which was comparable to commercial fungicide (Mancozeb) at 2.0 g L-1 (80.45 %). In vivo study showed that all plant crude extract at 15.0 g L-1 compounded disease incidence (DI) and disease severity (DS) due to phyto-toxicity. However, using dukung anak at 5.0 g L-1 or 10.0 g L-1 significantly controlled anthracnose and this was not different in turmeric-treated fruits at 10.0 g L-1 after 28 days of cold storage at 11 +/- 2 degrees C, 80 % RH. On the contrary, dragon fruits treated with ginger at 5.0 g L-1 and above experienced severe disease incidence due to phytotoxicity. In conclusion, crude extract of dukung anak or turmeric can be used as bio-fungicide to control anthracnose in dragon fruits at 10.0 g L-1 , while concentration at 15.0 g L-1 and above may exacerbate diseases in dragon fruits due to phytotoxicity.