Solanum habrochaites, S. Knapp & D. M. Spooner, S. Knapp & D. M. Spooner

Wang, Fumin, Park, Yong-Lak & Gutensohn, Michael, 2020, Glandular trichome-derived sesquiterpenes of wild tomato accessions (Solanum habrochaites) affect aphid performance and feeding behavior, Phytochemistry (112532) 180, pp. 1-11 : 3

2.3. Sesquiterpenes of two S. habrochaites chemotypes affect aphid feeding behavior

To characterize the potential effect of glandular trichome derived terpenes from different S. habrochaites chemotypes on M. euphorbiae in more detail we performed feeding assays. M. euphorbiae apterae were allowed to feed on an artificial diet to which aliquots of terpene containing leaf dip extracts from individual S. habrochaites accessions or S. lycopersicum c.v. M82 had been added. The survivorship of M. euphorbiae on these diets was determined, as well as the investment of gel saliva and the production of honeydew which serve as indicators of the aphid feeding behavior. A set of control experiments demonstrated that addition of methyl tert -butyl ether (MTBE), the solvent used for leaf dip extracts, as well as extracts from S. lycopersicum c.v. M82 to the feeding diet affected neither the survivorship of aphids ( Fig. 2A ) nor the accumulation of gel saliva ( Fig. 2B ) and honeydew drops ( Fig. 2C ) compared to pure feeding diet without added solvent or extracts. Addition of terpene containing leaf dip extracts from accessions of the S. habrochaites chemotypes 1, 2, and 3 to the diet did not appear to affect M. euphorbiae apterae as their survivorship (Supplemental Fig. S1A ) and feeding behavior measured by gel saliva investment and honeydew production (Supplemental Fig. S1B and C , respectively) were not significantly different compared to the performance of aphids feeding on a diet containing extracts from S. lycopersicum c.v. M82. In contrast, the performance of M. euphorbiae was severely affected when they were feeding on diets with added leaf dip extracts from the S. habrochaites chemotypes 4 and 5. The survivorship of aphids ( Fig. 2A ) on diets with the sesquiterpene blend extracted from accessions LA1775 and LA1779, as well as with the β- caryophyllene and α- humulene containing extracts from accessions LA1624 and LA2860 was significantly reduced compared to that of aphids feeding on diets with S. lycopersicum c.v. M82 derived extracts. Likewise, the investment of gel saliva and the production of honeydew by M. euphorbiae was significantly lower on diets with added extracts from S. habrochaites chemotypes 4 and 5 compared to the S. lycopersicum c.v. M82 control ( Fig. 2B and C ). The results of these feeding assays further confirmed the outcome of the previous non-choice assays and suggest that the sesquiterpenes produced in glandular trichomes of S. habrochaites chemotype 4 and 5 exhibit both antibiosis and antixenosis thus considerably affecting the performance of M. euphorbiae and altering their feeding behavior.

Figures

Fig. 2. Feeding performance of M. euphorbiae apterae on artificial diets containing leaf dip extracts of S. lycopersicum c.v. M82 and different S. habrochaites accessions (MTBE solvent control). (A) Kaplan-Meier estimates of survivorship and analysis of log-rank test (α =0.05). (B) Box and violin plots represent mean ±SE of gel saliva density (cm 2) and the probability density, respectively. (C) Number of honeydew drops accumulated in the feeding chambers. Asterisks in (B) and (C) represent significant differences between diets with leaf dip extracts and control based on Dunnett’s test (⋅, P <0.08; *, P <0.05; **, P <0.01; ***, P <0.001).

Fig. 1. Longevity (A) and fecundity (B) of M. euphorbiae apterae arrested on the leaf surface of two S. lycopersicum cultivars and different S. habrochaites accessions. Solanum habrochaites accessions represent five chemotypes characterized by the production of different sesquiterpenes in their glandular trichomes. Values for longevity and fecundity are presented as mean ± SE. Different letters indicate that logarithmic values were significantly different (Tukey’s HSD test, α = 0.05).