The host‐pathogen system of Gremmeniella abietina (Lagerb.) Morelet and Scots pine; effects of non‐pathogenic phyllosphere fungi, acid rain and environmental factors

Abstract

S i; M M .'\ R YScots pine seedlings (1-yr-old) were inoculated eitbe;-once, or three times, with the conidia of two saprophytic Hormonema species. After these inoculations, the seedlings were inoculated later with conidia of the pathogenic fungus Gremmeniella abietina (Lagerb.) Morelet. Seedlings received irrigation with simulated acid rain at pH 3, with water of pH 6, or no irrigation, during and after the inoculation treatments. The severity of tbe symptoms caused by G. abietina, and the isolation frequency of endophytic (symptomless) G. abietina and the saprophytes, were measured 11 months after G. abietina inoculation. The isolation frequencies of the two Hormonema species increased significantly in the seedlings inoculated three times witb saprophyte conidia. Irrigation treatments did not affect tbe saprophytes. The disease symptoms caused by G. abietma were positively correlated with tree density. Symptomless G. abietina was isolated most often from the seedlings that had received irrigation at pH 6. The isolation frequency was lowest in seedlings with acidic irrigation. The seedlings inoculated tbree times with conidia of Hormonerrta sp. 1 bad a lower frequency of G. abietina isolations than other seedlings, but the difference was not statistically significant.

Effects of sulphuric acid and heavy‐metal deposition on frequency of asymptomatic infections of Gremmeniella abietina in Scots‐pine seedlings

“…This parallels the results of earlier experiments which have shown that simulated acid rain (BRAGG and MANION 1984;VuoRiNEN 1990;RANTA and NEUVONEN 1994;RANTA et al 1995) and SO2 (LAURENCE et al 1984) alone do not, in the short term, increase the amount of G. abietina on pine. However, lowered soil pH may be related to increased disease occurrence (BRAGG and MANION 1984).…”

“…The positive effect of water irrigation on G. abietma was also detected in an experiment made with 2-year-old seedlings in the same study area (RANTA and NEUVONEN 1994). Precipitation and high air humidity are essential for the dispersal and survival of the conidia in the early stages of infection (BERGDAHL 1984;BARKEUND 1989), and the extra water may have been important in this respect.…”

Relationships between Vaccinium Vitis-Idaea and the Frequency of Its Fungal Pathogen Exobasidium Splendidum, and the Environment

“…Climate may contribute to the plantpathogen system by affecting the growth of the host plant populations or by affecting the growth, reproduction, and transmission of pathogens (e.g., Sundströ m, 1964;Ranta and Neuvonen, 1994;Green and Bayley, 2000;Roy et al, 2004). Availability of nutrients can affect the interaction between hosts and pathogens by altering the concentrations of amino acids in plant tissues (Strengbom et al, 2002).…”

Susceptibility of Six Scots Pine Clones to the Pathogenic Fungus Gremmeniella abietina

“…This variation, however, was connected with small-scale environmental factors but not with differences between clones. Site factors are known to affect Kurkela 1985, Ranta & Neuvonen 1994.…”

“…Both isolates were taken from adult Scots pine trees heavily diseased with Scleroderris canker and from branches situated at least 2.5 m above ground, to ensure that the isolates belonged to a type infecting shoots above the snow cover (Hellgren 1995, Uotila & Terho 1995. The fungi were isolated in the autumn of 1995 by placing surface-sterilized tissue on MA medium in Petri dishes (malt extract 2% and agar 1.5%; Ranta & Neuvonen 1994). The mycelium was then transferred to Erlenmeyr flasks containing a sterilized medium made of barleycorns and crushed pine needles.…”