Transcriptomic Analysis Reveals Resistance Mechanisms of Pecan ( <i>Carya illinoinensis</i> ) to <i>Colletotrichum fructicola</i> and Characterization of a Novel Resistance-Related Gene <i>CiCP12</i>

Carya illinoinensis (pecan) is an important fruit and woody oil tree species widely cultivated in China, but its production is severely affected by Colletotrichum fructicola . Transcriptome analysis indicated that the differentially expressed genes (DEGs) of pecan were significantly enriched in terms associated with disease resistance (e.g., defense response, protein autophosphorylation, and abscisic acid (ABA)-activated signaling) and pathways (e.g., plant-pathogen interaction, MAPK signaling, flavonoid biosynthesis). A key gene, named CiCP12, was screened and identified, which enhanced the resistance of Nicotiana benthamiana to C. fructicola infection by upregulating defense-related genes and having a higher basal antioxidant level. Conversely, silencing CiCP12 in pecan reduced resistance to C. fructicola infection by suppressing the expression of multiple defense-related genes. CiCP12 could also enhance broad-spectrum disease resistance against various pathogens in N. benthamiana . This study identified a key disease-resistance-related gene and provided insights into pecan defense mechanisms against C. fructicola .