T. Burgess et al., VARIATION IN MYCORRHIZAL DEVELOPMENT AND GROWTH-STIMULATION BY 20 PISOLITHUS ISOLATES INOCULATED ON TO EUCALYPTUS-GRANDIS W HILL EX MAIDEN, New phytologist, 127(4), 1994, pp. 731-739
Twenty isolates of Pisolithus, covering a range of hosts, basidiocarp
types and geographic locations were compared on their ability to form
mycorrhiza in vitro with Eucalyptus grandis and to stimulate seedling
growth in vivo. There was a large variation between isolates in the ra
te of mycorrhizal development and this was used to categorize isolates
into six types. Mycorrhiza of seedlings inoculated with type I isolat
es were the most advanced with a dual-layered mantle, a fully-develope
d Hartig net and radially elongated epidermal cells. Mycorrhiza of see
dlings inoculated with types II-V isolates were progressively less adv
anced so that mycorrhiza of type V isolates had a thin single-layered
mantle, the Hartig net was only partially developed and the epidermal
cells were not elongated. Root tips of seedlings inoculated with type
VI isolates were non-mycorrhizal. Inoculated seedlings were transplant
ed directly into undrained pots containing a yellow sand deficient in
phosphorus. Growth stimulation of E. grandis seedlings in the glasshou
se varied greatly between Pisolithus isolates, with dry weight increas
es ranging from two to 45 times that of the non-inoculated control see
dlings. Extent of mycorrhizal development was positively correlated to
growth stimulation in the glasshouse and it is proposed that this cou
ld be used as an indicator of isolate aggressiveness and consequently
the potential of an isolate to promote tree growth.