Variography and kriging allow screening Pinus pinaster resistant to Armillaria ostoyae in field conditions

Armillaria ostoyae is an important disease of Pinus pinasterin north-west Spain, which kills trees following a heterogeneousspatial structure. In a progeny trial of P. pinaster seedlings,spatial heterogeneity and autocorrelation of neighbour mortalitycaused by A. ostoyae impeded proper analysis of the diseaseincidence. We used variography and kriging methods to describethe spatial distribution of the infection probability and thegenetic variation of the resistance to A. ostoyae among families.The spatial structure of disease incidence was modelled, andthe probability of survival was corrected by kriging at eachtree location. Cumulative mortality 3 years after planting was65.1 per cent. Significant differences among P. pinaster familiesin terms of mortality to A. ostoyae were found, with low individual(h = 0.08) and moderate family (h = 0.35) heritability estimates. According to a theoretical semivariogram, the patch size ofthe disease incidence was 63 m wide. This is the first timevariography and kriging are used to select P. pinaster resistantto Armillaria root rot. It is concluded that geostatistics providesforest pathologists with a powerful tool for screening resistanttrees in field conditions.