Effect of pyroclastic cloud from Merapi volcano to the survival of Uromycladium tepperianum on Falcataria moluccana in Yogyakarta, Indonesia

摘要

Group of rust fungi have strong mechanism for adaptation and changed their pathogenecity under critical condition, including very high temperature. Merapi's eruption in November 2010 resulted in change of the morphological characteristics, survival and pathogenecity of U. tepperianum in Falcataria moluccana. Inoculums of U. tepperianum were taken from sengon trees in the Southern hill of Merapi volcano which showed symptoms of gall on 3 different distance of area affected by pyroclastic cloud, i.e. danger (3-7 km), alert (>7-ll km) and warning (>11-15 km) from the top of Merapi. Three locations from each distance were randomly chosen, namely fire (directly affected), border (indirectly affected) and green (completely uninfluenced) by pyroclastic cloud. Based on artificial inoculation test, pathogenecity of each inoculum was observed. The color, size and shape of teliospore as well as texture and color of gall were observed using qualitative and quantitative assessment. Survival and aggressiveness of U. tepperianum in the fire were lower than in the border or green location in all distances. However, in the border location itself, the spores of U. tepperianum is more pathogenic, represent by higher percentage of germination, penetration, and infection than in the both locations. This result was also supported by the characteristic of teliospores that were bigger, brighter, had better integrity shape (round) in the border location. One of obvious case due to local environmental changing caused by Merapi eruption was the increasing of aggressiveness of the gall rust disease caused by U. tepperianum on F. moluccana.