Genetic and phenotypic relationships between weevil (Pissodes strobi) resistance and height growth in spruce populations of British Columbia

Abstract

Strong genetic differences were demonstrated for both resistance to white pine weevil (Pissodes strobi (Peck)) attack and juvenile height growth in an open-pollinated progeny test of interior spruce. This test was a large (139 families), 10-year-old test in south central British Columbia with 8 years of accumulated weevil attack. Individual-tree heritability for genetic resistance was >0.4. Strong differences among families for this resistance was shown by a coefficient of variation of 46%. Besides strong family effects, the source of origin of parent trees, as indicated by biogeoclimatic zone, was a significant effect in the model. Individual-tree heritability was also high for juvenile height growth (>0.5). Although there is a significant positive phenotypic correlation (rP = 0.11) between leader growth and weevil attack (the weevils preferring longer leaders), there is a strong negative genetic correlation (rA = n0.61) indicating that inherently faster growing families have higher levels of genetic resistance. This high and favorable negative genetic correlation is accompanied by a positive environmental correlation of the same magnitude (rE = 0.46), indicating that environmental effects, which make longer leaders more attractive to the weevils, are independent of the fact that more vigorous families are more likely to have effective resistance to weevil attack.