Acidovorax citrulli (A. citrulli) strains cause bacterial fruit blotch (BFB) in cucurbit crops and affect melon significantly, up to 80-100% loss in production under favorable environmental conditions, especially during rainy seasons and highly fluctuating temperature regimes.
Scientists at Sunchon National University (Suncheon, South Korea) have found molecular markers for fast detection of A. citrulli strains. "Using a cross-inoculation assay, we have found that two Korean strains of A. citrulli, NIHHS15-280 and KACC18782, are highly virulent towards melon but a are virulent/mildly virulent towards the other cucurbit crops," the scientist explained.
Melon, watermelon, cucumber, and pumpkin plants were inoculated with different A. citrulli strains. The strains NIHHS15-280 and KACC18782 showing virulence only towards melon leaves and fruits at 12 and 7 Days After Inoculation, respectively. Typical BFB symptoms are indicated by white arrows.
The whole genomes of three A. citrulli strains isolated from melon and three from watermelon were aligned, allowing the design of three primer sets (AcM13, AcM380, and AcM797) that are specific to melon host strains, from three pathogenesis-related genes. These primers successfully detected both the target strain NIHHS15-280 in polymerase chain reaction (PCR) assays at a very low bacterial gDNA concentration and the target strains from artificially infected plant tissues, without requiring the extraction of bacterial DNA.
"This is the first report of molecular markers that offer reliable, sensitive, and rapid detection of strains of A. citrulli - the scientists conclude - These markers can detect melon host A. citrulli strains from asymptomatic fields prior to the appearance of symptoms, allowing farmers to employ timely control measures, test seed health prior to planting and ensure transboundary movement of disease-free seeds for quarantine purposes".
Source: Md. Rafiqul Islam, Mohammad Rashed Hossain, Hoy-Taek Kim, Denison Michael Immanuel Jesse, Md. Abuyusuf, Hee-Jeong Jung, Jong-In Park, Ill-Sup Nou, 'Development of Molecular Markers for Detection of Acidovorax citrulli Strains Causing Bacterial Fruit Blotch Disease in Melon', 2019, International Journal of Molecular Sciences, 20(11), 2715