Exploring Antagonistic Candidate Fungi for Controling Pathogenic Fungi (Colletotricum gloeosporioides) Causing Anthracnose Disease in Kintamani Siam Orange Plants (Citrus Nobillis Lour Var. Hass)

Abstract— Orange plantation centre in Bali are located in Bangli Regency, Kintamani District. Kintamani orange plantations cultivated three types of oranges: tangerine, selayar, and mandarin oranges. The famous orange in Bali today is Kintamani orange, tangerine type. The typical flavour and aroma of Kintamani tangerine make it is favoured by consumers from various regions. Based on the information from Bangli District Agriculture Office and the results of field surveys in the last two years (in 2013 and 2014), cultivation of orange in Kintamani has been infected with anthracnose disease. The disease is characterized by symptoms whereby brown twigs spread to the leaves and fruit, and the fruits which are about to be harvested rot simultaneously and eventually fall due to decay. This condition causes farmers to suffer significant losses. The cause of anthracnose on Kintamani orange is Colletotrichum gloeosporioides . The Control of these diseases has been carried out by farmers with various synthetic fungicides but the disease is still widespread. It is feared that the uncontrolled use of synthetic pesticides can harm the environment, cause resistance to C. gloeosporioides fungi, and kill non-target beneficial micro-organism. It is necessary to conduct research that aims to control anthracnose biologically to maintain the ecological balance and environmental safety. Based on the results of this research by exploring the fungi on healthy plants around orange trees infected with anthracnose diseases, nine isolates of antagonist candidate fungus were obtained based on colony colour of fungal hyphae (IS1, IS2, IS3, IS4, IS5. IS6, IS7, IS8, IS9). Based on the test results of the in vitro dual culture, two candidates of antagonistic fungal isolates were selected, the isolates IS4 and IS7. It was because on day 7 after the second dual culture, these two isolates had the highest percentage of inhibition, 89.22% and 85.11 % respectively. Based on the conventional and molecular identifications, it is known that the two candidate isolates of antagonistic fungus (IS4 and IS7) belong to one species of the Aspergillus aculeatus. Keywords— orange; antagonists fungi; kintamani tangerine; anthracnose; Cilletotricum gloeosporioides; Aspergillus aculeatus.