Field and Laboratory Detection of Clove Sumatra Disease Caused by Ralstonia syzygii subsp. syzygii in Java, Indonesia

Abstract

The significant decrease in clove production in Indonesia is mainly due to the Sumatra disease caused by bacterial Ralstonia syzygii subsp. syzygii. It is necessary to manage the disease broadly based on disease detection in the field and the laboratory. This study aims to determine the technique for detecting the distribution pattern of Sumatra disease using geographic information systems and validate the presence of R. syzygii subsp. syzygii in clove plant tissues by molecular analyses based on the endoglucanase gene. This research was conducted by acquiring aerial photos using uncrewed aerial vehicles processed using photogrammetric techniques to produce geographic information system outputs as a thematic map of the clove Sumatra disease distribution pattern. The plant samples were collected for molecular analysis of the pathogens causing clove Sumatra disease in the laboratory. DNA extraction was performed and amplified by polymerase chain reaction (PCR) using UGMRss-specific primers followed by Sanger sequencing. The aerial photo images showed that the distribution of clove Sumatra disease has a random pattern, which tends to spread between healthy and diseased plants. Furthermore, the PCR and phylogenetic analyses revealed that all symptomatic clove plant samples (leaves, twigs, and roots) were positively infected by R. syzygii subsp. syzygii.