Cadophora gregata

Cadophora gregata is a significant soil-borne fungal pathogen belonging to the Ascomycota phylum. It is the causal agent of Brown Stem Rot (BSR) in soybeans, a vascular disease that disrupts water and nutrient uptake, leading to severe yield reductions in many soybean-producing regions worldwide.

The host range is primarily limited to soybeans (Glycine max). The fungus enters the plant through the roots and migrates into the xylem tissues. Once established, it produces phytotoxins that degrade the plant's vascular integrity, causing the characteristic browning of the pith and inner stem tissue that gives the disease its name.

The life cycle of Cadophora gregata is characterized by its ability to persist as mycelia or conidia within infected crop residue in the soil for several years. Infection typically begins early in the season, but symptoms often remain latent until later stages of growth, particularly during reproductive phases when moisture demands are highest.

Environmental conditions play a critical role in disease severity. Cooler soil temperatures and high moisture levels during the early vegetative stages favor infection. As the season progresses, the fungus spreads upward through the stem, and under stress, it manifests as foliage wilting and interveinal chlorosis before the premature death of the plant.

Management of Brown Stem Rot requires an integrated approach. Genetic resistance is the most effective tool, and growers should select resistant soybean varieties. Additionally, long-term crop rotation (3-4 years) with non-host crops is essential to reduce the inoculum level in the soil. Tillage practices that promote the rapid decomposition of infected soybean debris are also recommended to disrupt the pathogen's life cycle.