Abstract:

Objective: To build a preliminary evaluation model of resistance to the damages of Curculio chinensis for Camellia oleifera based on fruit properties (capsule shape index, pericarp thickness, tea saponin content) of 8 Changlin clones of C. oleifera and C. chinensis's damage rate at four crucial stages (oviposition period, incubation period of larvae, developmental period of larvae and maturation period of larvae) to provide a theoretical basis for resistance breeding of C. oleifera. Method: The capsule shape index and pericarp thickness of 8 Changlin clones were measured during the peak of oviposition period. The accumulation of tea saponin was determined at four key periods. Finally the damage rate of each clone was counted. StepAIC() function in MASS package in R language was used to construct multiple linear regression model by using various measurements of the fruit properties as variables and the damage rate as dependent variables. Result: There were significant differences in capsule shape index between the 8 clones at the oviposition stage (P < 0.05), with a range of 0.5-1.2. Changlin No. 166 was long and elliptical, and the capsule shape index ranged from 0.5 to 0.7. Among the 8 clones, the pericarp thickness was between 3-6 mm, and the pericarp thickness of Changlin No. 53 was (5.03 ±0.08) mm which was higher than others. The pericarp thickness of all the clones was within the damage range of C. chinensis. The accumulation of tea saponin in the 8 clones at the four key stages showed to be different, and the tea saponin contents were obviously divided into three clusters. Based on the multivariate regression analysis of the 6 variables, the multivariate linear model with damage rate of C. chinensis (Y) as the dependent variable was preliminarily constructed:Y=0.531 6-0.301X₂-0.436 57X₄ + 0.059 526X₅-0.019 4X₆ (X₂:pericarp thickness; X₄:tea saponin content in incubation period of larvae; X₅:tea saponin content in developmental period of larvae; X₆:tea saponin content in maturation period of larvae). The regression model fitted well (P < 0.01, R²=0.773 7). Conclusion: The fruit properties (capsule shape index, pericarp thickness, tea saponin content) of C. oleifera were determined and analyzed. A multiple linear regression model was used to analyze the correlation between C. oleifera fruit properties and damage rate of C. chinensis in the four key periods. A preliminary evaluation model for the resistance to C. chinensis for C. oleifera was established. The establishment of the model is crucial for exploiting plant defensive traits in C. oleifera breeding to manage insect pests.

Key words: Curculio chinensis, Camellia oleifera, fruit properties, capsule shape index, pericarp thickness, tea saponin content, multiple linear regression model