Genomic Insights into the Pathogenicity and Host Adaptation of Pseudomonas amygdali pv. mori , the Causal Agent of Mulberry Bacterial Blight

Mulberry bacterial blight (MBB), a devastating disease of mulberry ( Morus spp.), causes substantial losses in yield and quality. This study isolated and characterized the highly virulent strain MYC18 from diseased tissues and identified it as Pseudomonas amygdali . The MYC18 genome comprises 6.39 Mb across a single chromosome and three plasmids, encoding 5,979 predicted coding sequences. Comparative genomic analysis indicates an open pan-genome and significant structural diversity among phylogenetically related strains. Genome annotation revealed 322 virulence-associated genes and 21 multidrug resistance determinants, along with a highly conserved type III secretion system (T3SS) encoding 29 predicted effectors. qRT-PCR analysis of eight representative T3SE genes revealed temporally partitioned expression patterns: early transient induction ( hopF1 , hopR1 , hopD2 ), sustained high expression ( hopI1 , hopM1 ), and late-peaking ( hopG1 , hopX1 , avrD ). As the first high-quality reference genome for P. amygdali pv. mori , the MYC18 assembly provides a critical genomic resource for elucidating the pathogenic mechanisms of mulberry bacterial blight and developing targeted disease control strategies.