Intraspecific variation in Heterobasidion annosum for mortality rate on Pinus sylvestris and Picea abies seedlings grown in pure culture

Abstract

One-month-old Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings were inoculated in vitro with Heterobasidion annosum strains, four each of the P-, S- and F-intersterility groups. Variation among strains and between the IS groups in virulence, expressed in mortality rate, was detected during twelve months after inoculation. Most of the strains were more virulent on spruce than on pine, and mortality of spruce seedlings was significantly higher. The P strains displayed similar virulence on both hosts, while S strains caused higher mortality of spruce seedlings and significantly lower mortality of pine seedlings. Strains of the F group were less virulent, but killed significantly (P < 0.05) more spruce than pine seedlings. In the interspecific analyses with two hosts, the isolates and IS groups accounted for most of the explained variation in the host mortality

• Heterobasidion annosum
• intersterility groups
• mortality rate in vitro
• Norway spruce
• Scots pine

This study was financially supported by the Polish Academy of Sciences and the Polish Committee for Scientific Research, grant No 5 P06H 004 15. The tester strains were kindly provided by Drs. Kari Korhonen from Finland, Paola Capretti from Italy, Panagihiotis Tsopelas from Greece, and Alenka Munda from Slovenia. We also wish to thank Mrs. Anna Błaszkowiak for her skillful technical assistance.