Pseudomonas fuscovaginae

The pathogen belongs to the kingdom Bacteria, genus Pseudomonas, species Pseudomonas fuscovaginae. These are gram-negative, motile, rod-shaped bacteria classified as facultative anaerobes.

The pathogen has the ability to produce specific enzymes that degrade plant cell walls and tissues. In laboratory settings, the bacterium produces a characteristic brown pigment on growth media.

Biologically, this species is adapted to temperate and tropical climates, where it persists in seeds and plant debris. The pathogen survives in soil for a limited period.

The primary mode of transmission is the use of infected seed material. Spread can also occur through irrigation water and contaminated agricultural tools.

In its natural environment, the bacterium can survive on weeds that serve as alternative hosts during the off-season.

The main crop affected by this phytopathogen is rice. The bacterium causes a disease known as bacterial sheath rot.

The pathogen infects leaf sheaths, stems, and inflorescences of plants. This disrupts the process of panicle emergence and the development of high-quality grain.

Severe infection results in empty panicles (panicle sterility), leading to significant yield losses. In some cases, plant death can occur at early developmental stages.

Besides rice, there is evidence of potential infection of other grass species under conditions favorable to the pathogen.

Economic losses include not only grain weight reduction but also the degradation of seed and quality characteristics.

Disease development is most active during periods of high humidity and moderate temperatures (from +15°C to +25°C).

Infection often manifests during the booting stage and the onset of rice flowering. Rain and heavy dew promote the rapid spread of bacteria across the field.

Extended periods of cool, wet weather create ideal conditions for epiphytotic development of the disease.

The development cycle includes primary inoculation via seeds and subsequent secondary spread via water droplets and wind.

The flowering period is critical, as the plant is most vulnerable to bacterial entry through natural openings.

Initial symptoms appear as dark brown or black stripes on the leaf sheaths surrounding the developing panicle.

Necrosis of the tissues is frequently observed on affected areas. Often, infected sheaths prematurely turn yellow and dry out.

The panicle enclosed in the infected sheath often fails to emerge fully, a process accompanied by tissue darkening and decay.

Under high humidity, a bacterial exudate in the form of droplets or a film may appear on the surface of the infected tissues.

Grains within the infected panicles are often stunted, grey or brown in color, and exhibit reduced germination rates.

The primary preventative measure is the use of healthy, certified seed material free from bacterial contamination.

Effective control methods include seed treatment with specific chemicals that suppress the growth of pathogenic bacteria.

An essential element of agronomy is crop rotation and the destruction of crop residues that serve as a source of infection.

Avoiding excessive nitrogen fertilization is necessary, as it encourages excessive vegetative growth and increases plant susceptibility to diseases.

In regions with a high risk of the disease, it is recommended to plant resistant rice varieties and conduct timely phytosanitary monitoring of crops.