Table 2.
Summary of the multiple regression analysis explaining the resistance to the pine weevil using the concentration of individual PSM as predictor variables in constitutive (upper part of the table) and in inducibility (lower part of the table) defensive modes in 102 genotypes from 10 maritime pine populations.
| Defensive mode | Plant secondary chemicals | β | Partial R2 |
|---|---|---|---|
| Constitutive PSM | β-Phellandrene + Limonene | -0.98 | 0.150 |
| (N = 87) | Lignan hexoside derivative 1 | -1.58 | 0.077 |
| Intercept = 7.908 | Ferulic acid | -0.33 | 0.028 |
| Model adjusted R2 = 0.70 | α-Copaene | -1.89 | 0.025 |
| F18,62 = 18.97 | Unk P11 | -0.35 | 0.024 |
| P < 0.001 | α-Cubebene + α-Longipinene | -0.76 | 0.016 |
| Coumaric acid hexoside | 0.60 | 0.079 | |
| Methyl thymyl ether | 0.57 | 0.054 | |
| α-Phellandrene | 0.52 | 0.040 | |
| Methyl eugenol | 0.87 | 0.035 | |
| Elemol | 0.75 | 0.031 | |
| Eugenol | 0.36 | 0.029 | |
| Bicyclosesquiphellandrene | 1.31 | 0.028 | |
| Myrcene | 0.56 | 0.022 | |
| Lignan xyloside derivative 2 | 0.40 | 0.021 | |
| Citronellyl propionate | 0.46 | 0.018 | |
| Sabinene | 0.53 | 0.015 | |
| Unk P6 | 0.39 | 0.011 | |
| Inducibility of PSM | Unk P5 | -22.46 | 0.234 |
| (N = 93) | Lignan hexoside derivative 2 | -19.17 | 0.060 |
| Intercept = -36.03 | Isopimaric acid | -10.05 | 0.060 |
| Model adjusted R2 = 0.68 | Elemol | -12.11 | 0.058 |
| F12,78 = 17.32 | cis-β-Ocimene | -9.04 | 0.048 |
| P < 0.001 | Methyl thymyl ether | -10.36 | 0.040 |
| Pimaric acid | -11.76 | 0.029 | |
| trans-Pinocamphone | -10.15 | 0.022 | |
| Oleic acid C18:1 | 10.03 | 0.048 | |
| Abietic acid | 31.24 | 0.039 | |
| Ferulic acid hexoside | 8.03 | 0.024 | |
| trans-β-Ocimene | 4.78 | 0.019 | |
The regression coefficients (β) and partial R2 of PSM included in the model after stepwise selection method are shown. PSM associated with resistance to weevil damage (negative β) are typed in bold. Linear regression model at each defensive mode is significant at p < 0.05. Genotypic sample size of each defensive state is indicated in brackets. Due to the fact that some clonal replicates (control or MJ-induced) were not available for several genotypes, sample size for the inducibility dataset was slightly lower than the original number of genotypes used. Unk P#, unidentified phenolic compound.