Bacterial canker of tomato: revisiting a global and economically damaging seedborne pathogen

The Gram-positive actinobacterium Clavibacter michiganensis is the causal agent of bacterial canker of tomato, an economically impactful disease with a worldwide distribution. This seedborne pathogen systemically colonizes tomato xylem leading to unilateral leaflet wilt, marginal leaf necrosis, stem and petiole cankers, and plant death. Additionally, splash dispersal of the bacterium onto fruit exteriors causes bird’s-eye lesions, which are characterized as necrotic centers surrounded by white halos. The pathogen can colonize developing seeds systemically through xylem and through penetration of fruit tissues from the exterior. There are currently no commercially available resistant cultivars, and bactericidal sprays have limited efficacy for managing the disease once the pathogen is in the vascular system. In this review we summarize research on epidemiology, host colonization, the bacterial genetics underlying virulence, and management of bacterial canker. Finally, we highlight important areas of research into this pathosystem that have the potential to generate new strategies for prevention and mitigation of bacterial canker.

Complete Genomic Data of Burkholderia glumae Strain GX Associated with Bacterial Panicle Blight of Rice in China

Burkholderia glumae is a seedborne pathogen causing bacterial panicle blight of rice. Here, we report the complete genome of B. glumae strain GX, which represents the first whole-genome sequence of an isolate from China. The assembled genome consisted of five contigs, with two circular chromosomes of 3,712,850 and 2,750,046 bp and three plasmids of 201,571, 105,587, and 96,100 bp. This complete genome will provide a valuable resource for further studies on bacterial panicle blight worldwide.

From Native Plants in Central Europe to Cultivated Crops Worldwide: The Emergence of Didymella bryoniae as a Cucurbit Pathogen

Didymella bryoniae (Auersw.) Rehm [anamorph Phoma cucurbitacearum (Fr.) Sacc.], the plant pathogenic fungus that causes gummy stem blight and black rot on cucurbits, was first described in 1869 from Bryonia (bryony or wild hops) in central Europe. Today, this pathogen is found on six continents on at least 12 genera and 23 species of cucurbits. How did D. bryoniae progress from a pathogen of a native plant in central Europe to a worldwide threat to cucurbits cultivated in humid environments? Clues from the early discoveries of this fungus, its characteristics as a seedborne pathogen, and its broad adaptation to cucurbit hosts will provide some answers to this question.