Transcriptomic and Physiological Analysis of the Effects of Exogenous Phloretin and Pterostilbene on Resistance Responses of Stylosanthes against Anthracnose

Anthracnose caused byColletotrichum gloeosporioidesis a destructive disease ofStylosanthes(stylo). Combination treatment of phloretin and pterostilbene (PP) has been previously shown to effectively inhibit the conidial germination and mycelial growth ofC. gloeosporioidesin vitro. In this study, the effects of PP treatment on the growth ofC. gloeosporioidesin vivo and the biocontrol mechanisms were investigated. We found that exogenous PP treatment could limit the growth ofC. gloeosporioidesand alleviate the damage of anthracnose in stylo. Comparative transcriptome analysis revealed that 565 genes were up-regulated and 239 genes were down-regulated upon PP treatment during the infection byC. gloeosporioides. The differentially expressed genes were mainly related to oxidative stress and chloroplast organization. Further physiological analysis revealed that application of PP afterC. gloeosporioidesinoculation significantly reduced the accumulation of O2•−level and increased the accumulation of antioxidants (glutathione, ascorbic acid and flavonoids) as well as the enzyme activity of total antioxidant capacity, superoxide dismutase, catalase, glutathione reductase, peroxidase and ascorbate peroxidase. PP also reduced the decline of chlorophyll a + b and increased the content of carotenoid in response toC. gloeosporioidesinfection. These results suggest that PP treatment alleviates anthracnose by improving antioxidant capacity and reducing the damage of chloroplasts, providing insights into the biocontrol mechanisms of PP on the stylo against anthracnose.Keywords:phloretin;pterostilbene;ROS scavenging;chloroplasts;anthracnose;stylo