Diseases

Phytophthora Root Rot of Alfalfa

Medicago sativa L.

Phytophthora root rot of alfalfa, caused by the oomycete Phytophthora medicaginis, leads to seedling death and stunting of mature plants, manifesting as reddish-brown lesions on the roots and yellowing of the foliage.

In the reference 41 varieties crop Alfalfa, where this is mentioned in the description.

The primary causal agent of alfalfa Phytophthora root rot is the oomycete Phytophthora medicaginis, previously classified as Phytophthora megasperma f. sp. medicaginis or Phytophthora cryptogea. In rare cases, the pathogen can be Phytophthora cactorum. The disease most frequently occurs in heavy, poorly drained soils and areas with standing water, where infected plants form characteristic patches.

At the seedling stage, seedling damping-off is observed, accompanied by stem constrictions at the soil surface. Mature plants exhibit stunting, yellowing or reddening of the leaves, and destruction of the root system. Water-soaked, reddish-brown lesions form on the roots, which eventually blacken, causing the taproot to rot and allowing the plant to be easily pulled from the ground.

A specific classification of pathogen races is not standardized, nor are alphanumeric designations for resistance genes. In agronomic practice, variety resistance is evaluated using resistance scales, such as "moderately resistant" or "highly resistant," and variety selection is based on proven breeding resistance to Phytophthora medicaginis.

General information about the subject — on the page Late blight.

Sources8

Varieties of Alfalfa mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.