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

Abstract

Bacterial fruit blotch (BFB) of cucurbits, caused by Acidovorax avenae subsp. citrulli, is a serious threat to the watermelon and melon industries. To date, there are no commercial cultivars of cucurbit crops resistant to the disease. Here we assessed the level of tolerance to bacterial fruit blotch of various commercial cultivars as well as breeding and wild lines of melon, using seed-transmission assays and seedling-inoculation experiments. Selected cultivars were also tested in a greenhouse experiment with mature plants. All tested cultivars/lines were found to be susceptible to the pathogen, and most of them showed different responses (relative tolerance vs. susceptibility) in the different assays; however, some consistent trends were found: cv. ADIR339 was relatively tolerant in all tested assays, and cv. 6407 and wild lines BLB-B and EAD-B were relatively tolerant in seed-transmission assays. We also provide evidence supporting a strong correlation between the level of susceptibility of a cultivar/line and the ability of the pathogen to adhere to or penetrate the seed. To the best of our knowledge, this is the first attempt to assess melon cultivars/lines for bacterial fruit blotch response.

Acidovorax citrulli: generating basic and applied knowledge to tackle a global threat to the cucurbit industry

“…Seeds produced in this manner transmitted BFB to seedlings once planted. In agreement with these findings, Bahar et al (2009b) reported that, under unfavourable conditions for BFB development, over 50% of seeds within asymptomatic melon fruits were infested with A. citrulli. Lessl et al (2007) reported that A. citrulli rapidly colonizes watermelon stigmas, and that there is a strong linear relationship between blossom inoculum dose and seed infection.…”

“…accessions and reported that four C. melo and one C. ficifolius plant introductions showed high levels of BFB resistance. Bahar et al (2009b) also reported BFB tolerance in cultivated and wild melons. They also reported that there was a difference in tolerance depending on the inoculation assay used, and that three cultivars/plant introductions-6401, BLB-B and EAD-B-were tolerant in seedling transmission assays, whereas cv.…”

“…In agreement with these findings, Bahar et al . () reported that, under unfavourable conditions for BFB development, over 50% of seeds within asymptomatic melon fruits were infested with A. citrulli .…”

Biological Control of Bacterial Fruit Blotch of Watermelon Pathogen (Acidovorax citrulli) with Rhizosphere Associated Bacteria

“…BFB, which is caused by Acidovorax citrulli , has been becoming a serious threat to farmers as it spreads through contaminated seeds and caused a significant economic losses in cucurbits worldwide (Bahar et al, 2009). The symptoms of BFB include greasy-appearing, water-soaked dark, olive-green stain, or blotch that develops on the upper surface of fruit which makes the fruit unmarketable and cause severe economic loss (Latin and Hopkins, 1995).…”

Efficacy of a Nonpathogenic Acidovorax citrulli Strain as a Biocontrol Seed Treatment for Bacterial Fruit Blotch of Cucurbits

“…For example, Bahar et al recently reported that, whereas certain melon cultivars had BFB-tolerant foliage, the BFB seed-toseedling transmission rates were still high (2). In the ab.sence of resistance there is a need to develop a comprehensive integrated disease management strategy for BFB.…”