Figure 1.
Arrangement of the experimental plots with the 6 maize inbred lines.
The enlargement shows the generalized location of the plants that were infested with Spodoptera frugiperda larvae inside the plot, the actual pattern being somewhat variable among the plots depending on the availability of suitable plants. The six plots to the left and the bigger plot with plants of the variety “Delprim” were used for volatile collections.
Figure 2.
Release of parasitoids and infestation of plants with caterpillars.
A) Numbers of female wasps and parasitized caterpillars released over the experimental period. B) Timing of infestation with neonate Spodoptera frugiperda larvae and of the subsequent recovery of the caterpillars remaining on the infested plants as well as of the volatile collections, whereby each line represents groups of plants that were infested together.
Table 1.
Average quantities (in ng; mean ± s.e; n = 12) of volatiles compounds collected in the field from the headspace of infested maize plants belonging to six different inbred lines.
Table 2.
Overview of the numbers of insects and their status after collection (begin) and after rearing out (end).
Figure 3.
Overview of the parameters assessed for six maize inbred lines arranged in order of increasing total volatile emission.
A-C) plant parameters; D-F) performance of the herbivore Spodoptera frugiperda; G-I) parasitism; J-L) natural infestation with herbivores and potential predators; n = number of plants; N = number of arthropods.
Table 3.
Correlation coefficients r (Pearson product moment correlations) between 6 maize inbred lines for the different parameters assessed in the field, i.e. the mean values shown in Figure 3.
Figure 4.
Performance of Spodoptera frugiperda caterpillars on the six maize inbred lines under laboratory and field conditions (r = 0.81; p = 0.0505).
Figure 5.
Total volatile emission of the six maize inbred lines according to collections conducted in the laboratory (six-arm olfactometer) as compared to collections carried out in the field (r = 0.92, p = 0.0093).
Figure 6.
Principal component analysis (PCA) of herbivore-induced volatile emission and of other plant parameters.
A) Biplots of a PCA of the 36 volatile compounds (for identity see Table 1) released by the individual maize plants. B) PCA of the average values for each line of the volatiles pooled into seven groups and of the other variates (A, B, D–L as in Fig. 3 and Table 3).