Screening and Evaluation of Non-Volatile Decision-Making Traits of Oviposition Resistance and Susceptibility of Bactrocera dorsalis

The objective of this study is to analyze the relationship between the non-volatile traits of peach fruit and the oviposition of Bactrocera dorsalis, determine the best indicator of the risk of injury and the range of resistance and susceptibility, and to clarify the classification correlation characteristics of the main indicators.

Using 13 representative peach varieties with different physical, villus, mineral elements and physiological characteristics as test materials, 60 non-volatile decision-making traits of 4 types were determined, and the selection test of the oviposition of B. dorsalis was carried out in the laboratory. The correlation and cluster analysis of the different traits and the average larval number in the fruit were carried out to determine the best indicator of the risk of injury and the range of resistance and susceptibility, and the performance of other main indicators was evaluated.

The average absolute value of the correlation coefficient between the 4 types of non-volatile decision-making traits and the average number of larvae was in the order of physiological indicators (0.21, 18 species)>fruit physics (0.19, 18 species)>villus indicators (0.18, 7 species)=mineral elements (0.18, 17 species). Simple correlation analysis showed that there were 17 indicators above the low correlation level. The absolute values of the correlation coefficient from large to small were magnesium (-0.57)>hardness (-0.53)>calcium (-0.52)>selenium (-0.48)>long/short of villus (-0.45)>density of long villus (-0.44)>shady facets-L* (0.43)>free amino acid (-0.41)>transverse diameter (0.38)>amylum (0.37)>salt (-0.35)>single fruit weight (0.33) = pH (0.33)>tannin (-0.32) = anthocyanin (-0.32) = fruit water content (0.32) = Synthesis-L* (0.32). Shady facets-L and magnesium content showed the maximum positive and negative correlation, respectively, the correlation coefficient of nitrogen and protein was 0. The three indicators of magnesium, hardness and calcium reached a significant correlation level, indicating that the medium elements and hardness had the greatest impact on the oviposition resistance of B. dorsalis. The comprehensive analysis showed that magnesium was the best indicator of peach fruit damage risk. According to the absolute value of magnesium content and the degree of fruit damage, cluster analysis method was used to determine those ≥1.50 g·kg^-1 as low-risk damaged varieties, that was the high-resistance variety, ≤0.92 g·kg^-1 was judged as high-risk victimized varieties, that was the susceptible variety, and the middle were neutral varieties.

The non-volatile trait of peach fruit affects the oviposition selectivity of B. dorsalis. Medium elements (magnesium, calcium) and hardness significantly affect the oviposition selection of B. dorsalis, and all show negative correlation. Magnesium was selected as the best indicator of peach fruit damage risk. There are differences in the effects of 14 low degree related decision-making traits such as selenium on oviposition preference, with 7 positive and 7 negative. The positive correlated traits are all physical indicators except for amylum and pH, while the negative correlated traits are mineral element (1), villus (2), and physiological (4) indicators. Based on the situation of fruit damage, individuals≥1.50 g·kg^-1 were preliminarily classified as high resistance varieties; ≤0.92 g·kg^-1 were susceptible varieties, while the middle were neutral varieties.