Suillus collinitus

The fruit body of Suillus collinitus is a medium to large, fleshy bolete. The cap is initially rounded, becoming convex and finally flat, reaching up to 11 cm (4.3 in) in diameter. The cap is covered with a brown cuticle of variable shade that is decorated with minuscule radial striations, which become more obvious in fully expanded specimens and especially in dry weather. The cap is often shaped irregularly and becomes viscid (sticky) when damp. The tubes are short and their stem attachment is usually slightly decurrent to adnate. The small and angular pores are yellow but darken with age. Young, fresh specimens sometimes bear droplets of a clear fluid that collect on the pore surface. The cylindrical stem is often short and stubby, typically 4–7 cm (1.6–2.8 in) tall by 1–2 cm (0.4–0.8 in) thick, coloured yellowish and ornamented with sparse reddish-brown granules. There is no ring. The base of the stem bears pink overtones and is attached to distinctively pink mycelial threads, which are visible when the fruit body is uprooted. The flesh is yellowish, thick and soft. In a colour reaction test with ammonia solution, the flesh turns reddish. The spores are seen ochre-brown in mass, but pale yellow when viewed with a light microscope. They are fusiform (tapered at each end), sized 8–10.5 by 3–4.5 μm. …

Suillus collinitus is found throughout Europe. It is an ectomycorrhizal fungus, forming mutually beneficial symbiotic relationships with several species of pine (Pinus). These include several two-needled European species of pine: Aleppo pine (P. halepensis) European black pine (P. nigra), stone pine (P. pinea), and Scots pine (P. sylvestris). The fungus favours limestone soils. S. collinitus is thermophilic, commonly occurring in southern Europe. It is rarely seen in more northern regions, such as the British Isles and Poland. It is red-listed in Denmark as near-threatened, and in Estonia as endangered. It has also been collected in Iran. The mushroom was reported in the municipality of Paipa, in the department of Boyaca, in Colombia. It was reported by mycologyst Juan Camilo Rodríguez Martínez.

Suillus collinitus is the most frequent fungus associating with Aleppo pine – a hardy tree utilised for reforestation schemes and soil conservation against erosion in the Mediterranean region. A study performed in the south of France discovered that S. collinitus and S. mediterraneensis are multi-stage ectomycorrhizal fungi, associating with both young and mature stands of Aleppo pine. These two species may play a key role in the survival and adaptation of this species of pine on disturbed calcareous sites. Roots mycorrhizal with S. …