Pisolithus Isolates Research Articles

Variation in mycorrhizal development and growth stimulation by 20 Pisolithus isolates inoculated on to Eucalyptus grandis W. Hill ex Maiden.

Twenty isolates of Pisolithus, covering u 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 rate of mycorrhizal development and this was used to categorize isolates into six types. Mycorrhiza of seedlings inoculated with type I isolates were the most advanced with a dual-layered mantle, a fully-developed Harris net and radially elongated epidermal cells. Mycorrhiza of seedlings inoculated with types II V isolates were progressively less advanced 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 lips of seedlings inoculated with type- VI isolates were non-mycorrhizal. Inoculated seedlings were transplanted directly into undrained pots containing a yellow sand deficient in phosphorus. Growth stimulation of E. grandis seedlings in the glasshouse varied greatly between Pisolithus isolates, with dry weight increases ranging from two to 45 times that of the non-inoculated control seedlings. Extent of mycorrhizal development was positively correlated to growth stimulation in the glasshouse and it is proposed that this could be used as an indicator of isolate aggressiveness and consequently the potential of an isolate to promote tree growth.

In vitro mycorrhization of Casuarina and Allocasuarina species by Pisolithus isolates

Five Casuarina species and five Allocasuarina species were inoculated in vitro with three isolates of Pisolithus sp. (Ors.X004 and Ors.7870 from Senegal, PR86 from Australia) to test their ability to form ectomycorrhizas. The mycorrhiza-forming ability varied between fungal isolates. The greatest differences occurred between Casuarina and Allocasuarina species. On Casuarina species, Pisolithus isolates formed only a fungal sheath. However, Ors.X004 induced well-developed ectomycorrhizas on Casuarina equisetifolia, whereas PR86 failed to form any fungal sheath on Casuarina cunninghamiana. On Allocasuarina species, Pisolithus isolates formed generally well-developed ectomycorrhizas. In addition, isolates Ors.7870 and PR86 invaded the cortical cells of Allocasuarina luehmannii and Allocasuarina decaisneana, respectively, thus forming ectendomycorrhizas. Epidermal cells of both Casuarina and Allocasuarina mycorrhizas showed tannin deposits. In fully developed ectomycorrhizas, the epidermal cells were radially elongated and the Hartig net never developed beyond the epidermal cells. In general, the ability to form ectomycorrhizas was more common with the genus Allocasuarina than the genus Casuarina.Key words: Casuarina, Allocasuarina, Pisolithus, ectomycorrhizas.

Effects of Aluminum and Manganese on the Growth of Ectomycorrhizal Fungi

Cenococcum graniforme, Suillus luteus, Thelephora terrestris, and three isolates of Pisolithus tinctorius were cultured on modified Melin-Norkrans medium at pH 3.4 and adjusted to 0 to 500 ppm (0 to 500 mug/ml) of aluminum or manganese sulfate. Except for T. terrestris, which was intolerant of aluminum at 150 and 250 to 500 ppm, and P. tinctorius isolate 250, which was intolerant of aluminum at 450 ppm, all fungi showed some growth at all concentrations of aluminum. S. luteus was the most tolerant to aluminum. Manganese was less fungitoxic than aluminum, with all fungi showing at least 65% growth at 500 ppm as compared with the control. C. graniforme was not inhibited at any concentration of manganese, and S. luteus was only affected at 500 ppm. P. tinctorius isolate 230 showed no significant variation in growth when subjected to various concentrations of three forms of manganese salts. Significant differences in growth were detected in response to three aluminum salts, but no detectable pattern was apparent. Genotypic responses to aluminum and manganese were evident for P. tinctorius. Isolates 210 and 230 were more tolerant to manganese than was isolate 250. Aluminum tolerance was in the order of isolate 230 > 210 > 250. Results of in vitro studies concerning tolerance responses of ectomycorrhizal fungi to aluminum and manganese were not consistent with field observations of the successional sequence of these fungi on acid coal spoils.