Pink rib

Pink rib is a physiological and pathological disorder primarily affecting lettuce crops during maturation and post-harvest handling. The condition is associated with Pseudomonas bacteria, particularly Pseudomonas marginalis, which colonize the tissue, causing the characteristic discoloration that gives the disease its name.

The disease exclusively targets lettuce (Lactuca sativa). The initial symptoms are manifested as pink or reddish discoloration of the midrib, which can subsequently progress to involve the entire leaf blade. In advanced stages, the affected tissue undergoes necrosis, turning brown and becoming susceptible to secondary bacterial soft rot.

Environmental conditions play a crucial role in the development and spread of Pink rib. High temperatures during the head-filling stage and excessive nitrogen fertilization are recognized as primary triggers. Furthermore, post-harvest temperature fluctuations significantly exacerbate the disease, as they create an ideal environment for bacterial proliferation.

The economic impact of Pink rib is significant, primarily due to the rejection of produce. Even minor discoloration makes the lettuce unmarketable according to high retail standards. Furthermore, the presence of the disease significantly shortens the shelf life of the product, leading to increased waste during distribution and storage.

Management of Pink rib relies on integrated agricultural practices. Key preventive measures include harvesting in the early morning hours, prompt cooling of the crop, and maintaining consistent cold chain temperatures (near 0°C) during transport. Growers are also advised to use balanced fertilization plans and select cultivars known for their resistance to physiological stress.