Influence of temperature on the mycorrhizal associations of Pinus radiata D. Don

Abstract

The growth on Melin-Norkrans medium by 12 out of 13 isolates (five species) of mycorrhizal fungi declined rapidly between 20 and 16°C, as did colonization of the rhizosphere of Pinus radiata by four out of five isolates (three species). Mycorrhizal production in soil was optimal at 25° and declined markedly between 20 and 15°.

Large differences occurred between strains within a fungal species in length of root colonized and in the intensity of growth on the root at 16°C. Extremely poor colonization by some fungi at 16° compared with 20° reveals a necessity to select fungi for field inoculation on the basis of root colonization at soil temperatures appropriate to the area and season as well as on ability to stimulate plant growth. The effect of tem- perature on the linear growth of different fungal isolates in a rich laboratory medium was a poor guide to their growth in the rhizosphere.