Assessment of Needle Cast Resistance in Young Scots Pine Plantations in Latvia

摘要

Needle cast (Lophodermium seditiosum Minter, Staley & Millar) is pathogenic fungi species that affect one-year old needles of Scots pine and is predicted to increase in importance in future climatic and forest management conditions. Therefore the aim of the study is to evaluate differences in needle cast resistance and impact of this disease on survival of young Scots pines. Data for the study were obtained from geographical provenance trial, located in 3 climatically different sites and including altogether 56 provenances and average samples from six phenotypically selected Latvia's Scots pine seed orchards. Data were obtained also from a set of 2 nursery trials, including 15 provenances represented by 282 open-pollinated families. The level of needle cast damage was classified in a five grade scale, based on the percentage of needles damaged by the disease in the shoots of last year. Results reveal significant (p=0.01), but small differences among pines from separate provenance regions in needle cast damage grade. Provenance and family has significant (p=0.01) and pronounced effect on the level of the needle cast damage. That indicates a potential for improvement of the resistance through selection process. Site x provenance interaction is non-significant, ensuring higher precision and effect of selection. The need for improvement of the resistance is emphasized by findings, that correlation between needle cast damage grade and survival in the second growing season is strong and significant and significantly (p=0.01) larger needle cast damage is observed in locations with milder climatic conditions, similar to those predicted in future.