Keragaman cendawan endofit pada buah kakao dan potensinya dalam pengendalian busuk buah phytophthora

Abstract

Endophytic fungi have been reported capable to suppress development of black pod disease in cacao. In Indonesia, research on endophytic fungi in general has just been started. The aim of this study were to investigate factors related to the incidence of black pod disease in the field, to explore the diversity of endophytic fungi during ENSO simulation period and its correlation to black pod disease, and to examine the potency of selected endophytic fungi in controlling black pod disease. Field observation was conducted in Palolo and Kulawi, cacao plantations located at the border of Lore Lindu National Park, Central Sulawesi, laboratory and greenhouse experiments were performed at Bogor Agricultural University, Bogor, Indonesia and Georg-August University, Goettingen, Germany. Black pod disease incidence was highest in plots that: were located at > 600 m a.s.l.; which were previously occupied by pristine forest or perennial plants; had prior intensive inputs of pesticides and fertilizers; and had a high frequency of weeding. While application of nitrogen fertilizer, distance to pristine forests, plant age, canopy cover, diversity of endophytic fungi and degree of shading by shade trees were not associated with the disease development. A total of 2843 isolates were obtained from 1440 husk segments of healthy pods. By morphological and molecular techniques, the identification of these isolates resulted in 37 species of fungi, six belong to Basidiomycetes, 30 are Ascomycetes and one is unidentified yet. The diversity of endophytic fungi, based on Shannon’s and Simpson’s index, was higher during lower rainfall (January-April 2008) compared to higher rainfall condition (March-April 2007). The dominance of endophytic fungi changed with season, Fusarium lichenicola was the most dominance during wet condition and Phomopsis columnaris during dry condition. Several species, such as Fusarium sp. T47a, Xylaria sp., Polyporaceae DIS 126a, Aschersonia sp., Calocybe gambosa, and Xylariaceae were negatively correlated to the incidence of black pod disease. Among the tested endophytic fungi, Xylariaceae and Callocybe gambosa generated the highest effectiveness control level of black pod disease on detached pods, 38.8% and 33.8%, respectively, followed by Resinicium friabile and Aschersonia treatment, 17.4% dan 12.7% respectively. Growth inhibition of pathogen and induced resistance of plant were partially responsible for disease suppression by Xylariaceae, C. gambosa, R. friabile and Aschersonia sp.