First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Cucumber

Abstract

In March 1999, a foliar bacterial disease was observed in a commercial crop of cucumber (Cucumis sativus L.) cv. Jetset in Gumlu in northern Queensland, Australia. Initial symptoms consisted of angular, chlorotic, water-soaked lesions that later dried to necrotic areas of light brown, dead tissue. White bacterial ooze was commonly found on the undersides of young water-soaked lesions. Lesions were delimited by veins and distributed uniformly over leaf surfaces, and more than 20% of the crop was affected. No symptoms were observed on plant stems or fruits. Bacterial streaming from the edges of freshly cut young lesions was clearly visible in a droplet of water under ×100 magnification in the laboratory. Isolations were made from young lesions on King's medium B (1). A slow-growing, white, gram-negative, nonfluorescent bacterium was consistently isolated. Three isolates of the bacterium were identified, using the Biolog software program (Biolog, Hayward CA), and in each instance, the bacterium was confirmed as Acidovorax avenae subsp. citrulli, with a similarity of >0.80. Koch's postulates were completed with 8-day-old glasshouse-grown cucumber (cv. Jetset) seedlings. Seedlings were misted until runoff with a bacterial suspension of 3 × 108 CFU/ml and enclosed in plastic bags for ≈30 h at 22°C. Water-soaked lesions were observed on cucumber cotyledons 4 days after inoculation. This is the first report of A. avenae subsp. citrulli as a pathogen of cucumber. Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

Origins and Recombination of the Bacterial-Sized Multichromosomal Mitochondrial Genome of Cucumber

“…The bacterial plasmid-like sequence appears to have been transferred from Acidovorax, a destructive seed-borne pathogen and the cause of bacterial fruit blotch in cucumber (Martin et al, 1999) and other cucurbit crops (Makizumi et al, 2011). The mitochondrial genome of Vitis (grapevine) also contains foreign pathogenic sequence, in this case acquired from a grapevine leafroll-associated virus (Goremykin et al, 2009).…”

Bacterial fruit blotch of melon: screens for disease tolerance and role of seed transmission in pathogenicity

“…The disease started to gain importance after severe outbreaks in watermelon fields in the USA during the late 1980s/early 1990s (Wall and Santos 1988;Wall et al 1990;Somodi et al 1991). Since then, BFB has been reported in other cucurbits, such as melon, pumpkin and cucumber, and has spread to many parts of the world, including the Americas, Asia, Europe, the Middle East and Australia (Isakeit et al 1997(Isakeit et al , 1998Langston et al 1999;Martin and O'Brien 1999;O'Brien and Martin 1999;Schaad et al 2003;Walcott et al 2004;Burdman et al 2005).…”

Differences in Pathogenicity between two Genetically Distinct Groups of Acidovorax avenae subsp. citrulli on Cucurbit Hosts

“…Recent trends of devastating BFB outbreaks in melons, pumpkin, cucumber, bitter and bottle gourds in Costa Rica, Brazil, China, Australia, Nicaragua and Taiwan suggest that the host range of A. avenae subsp. citrulli has expanded (Assis et al., 1999; Langston et al., 1999; Martin and O'Brien, 1999; O'Brien and Martin, 1999; Cheng et al., 2000; Zhao et al., 2001; Martin and Horlock, 2002; Munoz and Monterroso, 2002). While the recent increase in reliance on greenhouse‐grown transplants for cucurbit production could be contributing to BFB outbreak frequency, it is more likely that increases in BFB on non‐watermelon hosts are due to changes in the population structure of the pathogen.…”

“…citroides ), prickly paddy melon ( C. myriocarpus subsp. myriocarpus ) and several types of gourds in the USA, Australia, Costa Rica, Nicaragua, Taiwan, China, Japan and Brazil (Isakeit et al., 1997, 1998; Assis et al., 1999; Langston et al., 1999; Martin and O'Brien, 1999; O'Brien and Martin, 1999; Cheng et al., 2000; Shirakawa et al., 2000; Zhao et al., 2001; Martin and Horlock, 2002; Mora‐Umana and Araya, 2002; Munoz and Monterroso, 2002).…”