Corynebacterium flaccumfaciens

Systematic position and pathogen nature: Corynebacterium flaccumfaciens (currently classified as Curtobacterium flaccumfaciens) belongs to the kingdom Bacteria, phylum Actinomycetota, and the genus Curtobacterium. It is a Gram-positive, aerobic, non-motile rod-shaped bacterium known as a destructive plant pathogen that primarily colonizes the vascular system.

Diseases and host plants: This organism is the primary cause of bacterial wilt in common beans. It also affects other legumes such as soybeans and peas. The typical symptoms include wilting of leaf margins, yellowing, and eventual tissue necrosis, which results in the wilting and death of the entire plant.

Biology and life cycle: The pathogen survives within infected seeds, soil, and crop debris. Infection occurs through wounds or natural openings like stomata. Once inside, the bacteria multiply rapidly in the xylem, clogging it and obstructing water transport. Dissemination in the field is facilitated by rain splashes, irrigation, contaminated tools, and insect vectors.

Conditions for development: The development of the disease is highly favored by warm temperatures, typically ranging from 24 to 30 °C, combined with high humidity. Frequent rainfall and prolonged warm periods significantly accelerate the spread of the pathogen, leading to rapid disease progression throughout the field.

Harmfulness and control measures: Due to the severity of the disease and the lack of effective curative chemical treatments, integrated management is essential. Prevention is the cornerstone of control:

• Use of pathogen-free, certified seeds.
• Implementation of crop rotation cycles to break the infection chain.
• Proper disposal of plant residues after harvest.
• Deployment of resistant crop varieties and strict management of insect populations that may spread the bacteria.