White spruce resistance against the spruce budworm : genetic control and insect-host interaction

Authors: Méndez Espinoza, Claudia
Advisor: Bauce, ÉricMacKay, John
Abstract: Picea glauca (Moench) Voss (white spruce) is one of the main hosts of the spruce budworm (SBW), anepidemic defoliator that is the most damaging in forests of eastern North America causing tree mortality and large economic losses. A constitutive resistance mechanism against the SBW was recently discovered. In this thesis, we studied this mechanism based on the foliar accumulation of aglycon acetophenones ̶piceol and pungenol ̶resulting from the expression of the Pgglu-1gene; and we refer to them as resistance biomarkers. Picein, the glycoside precursor of piceol was also investigated and we refer to all four traits togetheras defense biomarkers. The first part of this thesis presents a quantitative genetic study, which analysed 874 trees representing 33 full-sib families and 71 clonal lines from seven field locations in Eastern Canada. The goals were to i) determine the genetic control of the defense biomarkers, ii) estimate the genetic and phenotypic correlations among the four defensive traits and growth, and iii) evaluate the occurrence of trade-offs between the defense biomarkers and primary growth. Narrowsense heritability of piceol, pungenol and Pgglu-1 gene expression was moderate (0.55, 0.50 and 0.58, respectively). Slightly higher broad sense heritability estimates were obtained for acetophenones (0.66 and 0.60 respectively), indicating that additive genetic effects playa major role in these resistance biomarkers. Positive genetic correlations were found between the resistance traits and growth (from 0.14 to 0.30), suggesting that the resistance mechanism does not compromise growth in white spruce. In the second partof the thesis, we studied the insect-host interaction by use of insect rearing trials in severalwhite spruce clones. Our objectives were to iv) characterize the developmental and phenological variation of the defense acetophenones, v) evaluate the impact of the matched and delayed host phenology windows on the biological performance of the SBW, and vi) assess the inducibility potential of the resistance traits. Weshow that there are considerable variations in the acetophenone accumulation profiles between individual trees supporting their classification as Resistant (R) and Non-Resistant (NR); that the efficiency of the resistance traits is influenced by the synchronization between the P. glauca phenology and the insect feeding. Finally, we show that the resistance mechanism can be inducible.
Document Type: Thèse de doctorat
Issue Date: 2018
Open Access Date: 7 March 2019
Permalink: http://hdl.handle.net/20.500.11794/33970
Grantor: Université Laval
Collection:Thèses et mémoires

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