Fig. 4.

SA content and expression of genes involved in the SA signaling pathway in two Medicago truncatula genotypes grown under well-watered or drought conditions with and without pea aphid infestation. (a) SA content; (b) pathogenesis-related protein (PR); (c) β-1,3-glucanase (BGL); and (d) endochitinase (CHTN) expression. Each value is the mean (±SE) of eight replicates. Different lower case letters indicate significant differences among the combinations of aphid treatment and water treatment within the same genotype. Different upper case letters indicate significant differences between genotypes within the same water treatment and aphid treatment as determined by Tukey’s multiple range test at P<0.05.