Influence of Genotype and Transcriptional Regulation on The Response of Oil Palm (Elaeis guineensis) to Curvularia oryzae Induced Leafspot Disease

Abstract

Oil palm is one of the most productive oil crops, with a global value of USD 50.6 billion in 2021. It is prone to biotic and abiotic stresses, which place major constraints on productivity. Leaf spot disease can significantly impact productivity if not controlled. Breeding resistant varieties is the most economical, effective, and promising strategy. A Genome-Wide Association Study of 210 individual Tenera palms from 7 different (origin) crosses identified genetic loci associated with disease resistance. Two loci on chromosome 2 and chromosome 13 were shown to be significantly associated with leafspot disease resistance. Six genetic variants at the two loci surpassed the threshold for genome-wide significance (p< 10⁻6). These loci are linked to three widely known disease-related genes, analogue 3 (RGA3), analogue 4 (RGA4), and receptor-like protein 9a (RLP9a), which can be used for marker-assisted selection. AUDPC analysis and Kaplan-Meier survival test identified two progenies as highly resistant (G10 and G12), whilst others of similar origin with one progenitor in common were susceptible (G14 and G26). RNA sequencing identified 1,225 differentially expressed genes in the susceptible progeny in response to infection compared to 243 DEGs in the resistant progeny, with 42 common to both progenies. Further studies identified >1,800 DEGs between four different timepoints, whilst only 170 DEGs were found between different progenies. Several genes and transcription factors related to disease-resistance such as RGA, WRKY, WAKL and PR proteins were identified as playing an important role in leafspot disease resistance. These are the first reports of C. oryzae-induced gene expression in oil palm and provide potential molecular targets for breeding programmes.