Mevalonate pathway genes expressed in chilli CM334 inoculated with Phytophthora capsici and infected by Nacobbus aberrans and Meloidogyne enterolobii

The chilli pepper landrace CM334 (Capsicum annuum L.) is resistant to Phytophthora capsici (Pc), but susceptible to Meloidogyne enterolobii (Me) and Nacobbus aberrans (Na). Resistance to Pc is associated with capsidiol (sesquiterpene phytoalexin). To know the transcriptional alterations that Na or Me induce in CM334 plants, the expression levels of some genes of the mevalonate pathway were determined by RT-qPCR. At 3 or 21 days after inoculation with nematode (dai), plant stems were inoculated with Pc (NaPc and MePc treatments), furthermore, there were also plants inoculated only with Pc, Na, and Me. At 6, 24 and 48 h after inoculation with Pc (haio), the transcripts accumulation of HMG2 (hydroxymethylglutaryl-CoA reductase 2), EAS (5-epiaristolochene synthase) (associated with sesquiterpene phytoalexin biosynthesis), HMG3 and SS genes (squalene synthase) was assessed; also capsidiol accumulation was evaluated at 144 haio. The transcript levels were generally lower in NaPc, MePc, Na and Me than those recorded in the Pc treatment (p˂0.05) at 3 and 21 dai with Na or Me. Only when Pc was inoculated at 21 dai with the nematode, the capsidiol levels were significantly lower in stems of plants infected by NaPc and MePc compared to Pc treatment. In contrast, in roots the differences between Pc vs NaPc and Pc vs MePc, were significant both at 3 and 21 dai (p˂0.05). The two nematodes altered the expression of defense genes systemically (stems), and reduced capsidiol levels locally and systemically, possibly to create a favorable environment that allowed them to complete their life cycle.