Bacterial seed decay

Bacterial seed decay, triggered by the bacterium Bacillus subtilis, is a significant pathology affecting various leguminous crops, with soybean being particularly susceptible. Although this bacterium is often utilized in bio-fertilizers, it can behave as a pathogen under conditions of high soil moisture, causing the decomposition of seeds before or during germination.

The primary symptoms include the softening and discoloration of seeds, often accompanied by a slimy appearance and an unpleasant smell of decay. Affected seeds exhibit inhibited germination, and if they do sprout, the seedlings often appear necrotic or stunted. In many cases, the seeds completely rot within the soil, leaving empty gaps in the crop stand and reducing the overall plant population density.

The development and spread of the disease are heavily influenced by environmental conditions, particularly prolonged cold and wet weather immediately following planting. High moisture levels in the seedbed, combined with poor soil aeration, create an ideal environment for the bacterial population to multiply rapidly on the seed coat. Mechanical damage to seeds during harvesting also significantly facilitates the infection process.

The economic impact of this disease is primarily associated with reduced field emergence and poor crop establishment. Low plant density significantly limits the yield potential of the soybean field. Furthermore, seeds that are colonized by bacteria but manage to produce seedlings may develop into weak, vulnerable plants, making the crop more susceptible to secondary fungal or bacterial infections throughout the growing season.

Effective management requires a combination of strategies. The use of high-quality, certified seeds that have been properly treated with fungicides and bactericides is essential. Farmers should avoid planting in cold, waterlogged soils and prioritize good seedbed preparation to ensure rapid emergence. Additionally, maintaining proper crop rotation and avoiding excessive soil compaction helps reduce the pathogen's ability to survive and thrive in the field.