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Research
The Department of Plant Pathology and Microbiology
The Robert H. Smith Faculty of Agriculture, Food and Enviroment
The Hebrew University of Jerusalem
Basic and applied research on bacterial fruit blotch (BFB) disease
Acidovorax avenae subsp. citrulli (Aac) is the causal agent of bacterial fruit blotch (BFB) disease of cucurbits. BFB gained attention after several devastating outbreaks in watermelon fields in the US during the late 80s'. Then, in few years the pathogen spread to many parts of the world mainly through seed transmission, and today it is a serious threat in several countries at the Americas, Europe, Asia, the Middle East, and Australia. In addition to watermelon, several other cucurbit plants are affected by the pathogen, including melon, cucumber and pumpkin. Since Aac is a seedborne pathogen and there is a lack of reliable methods for its detection in infested seeds, BFB is also a serious threat for seed companies and seedling nurseries. We are cooperating with other researchers to develop more efficient and reliable techniques for detection of Aac in contaminated seed lots as well as screening for BFB resistance sources.
We are also conducting basic research to increase our knowledge on BFB pathogenesis. Despite the economic importance of BFB, very little is known about the basis aspects of this disease. We optimized molecular techniques as well as inoculation assays and we are screening for bacterial genes that contribute to virulence of Aac. We have found that a functional Hrp-type III secretion system is required for Aac pathogenicity, and also demonstrated that polar flagella and type IV pili play an important role in virulence of this pathogen.
Our collaborators in Aac projects are Prof. Ron Walcott (University of Georgia, USA), Prof. Bingyu Zhao (Virginia Tech, USA), Prof. Gregory Welbaum (Virginia Tech, USA), Prof. Leonardo De La Fuente (Auburn University, USA) Dr. Johannes Sikorski (DSMZ, Germany) and Dr. Shulamit Manulis-Sasson (Volcani Center)
Cucurbit plants affected by Aac following different inoculation
methods. A-F: Foliar
inoculation of 3-week-old seedlings: melon (A, D), cucumber (B, E) and watermelon (C, F)
inoculated with strains M6 (A-C) and W1 (D-F). Arrows indicate inoculated leaves. Pictures
were taken 7 days after inoculation (d.a.i.). G: Seed inoculation of melon with bacterial
suspensions of strain M6 (highly virulent on melon; right), strain W1 (weakly virulent on
melon; middle), or water (left). Picture was taken 10 d.a.i. H-I: Inoculation of detached
fruits (H-J): watermelon inoculated with strain W1 (H, I); melon inoculated with strain M6.
Pictures were taken 5 d.a.i. (Burdman et al., Plant Disease 2005).