Early Detection of Asian Soybean Rust Using PCR

Abstract

Early detection of Asian soybean rust (ASR) is essential to help producers minimize the impact of this serious disease. DNA from ASR-infected soybean plants was used to compare conventional and real-time ASR-specific PCR assays at seven laboratories in the United States. Soybean plants were inoculated with four concentrations of rust spores to establish different levels of infection within the plants. Plant tissue was then harvested at 7 time points over the course of 12 days, and DNA was extracted using two commercially available kits. DNA extracted from soybean plants inoculated with different spore concentrations was tested for ASR using conventional or real-time PCR assays. ASR was consistently detected at 6 days following inoculation with both the conventional and real-time PCR assays. This study demonstrates the ability to reliably detect ASR in soybean before the presence of readily visible symptoms. It also demonstrates the reproducibility of the PCR assay across different real-time PCR platforms at multiple laboratories when the assays were performed in multiple diagnostic laboratories. Accepted for publication 5 April 2006. Published 24 May 2006.