The autophagy-related protein PlAtg26b regulates vegetative growth, reproductive processes, autophagy, and pathogenicity in <i>Peronophythora litchii</i>

<i>Peronophythora litchii</i> is an oomycete pathogen responsible for litchi downy blight, a significant threat to global litchi production. Autophagy, a conserved degradation pathway crucial for the growth, development, and pathogenicity of phytopathogenic organisms, remains an area of active investigation. In this study, we characterized the function of the Atg26 homolog PlAtg26b in <i>P. litchii</i>. Using the CRISPR/Cas9 genome editing system, we generated <i>PlATG26b</i> knockout mutants and determined that PlAtg26b localizes to mitochondria under stress conditions. Although deletion of <i>PlATG26b</i> did not impair selective autophagy, it markedly reduced Atg8-PE synthesis, vegetative hyphal growth, asexual and sexual reproduction, and zoospore release. Furthermore, <i>PlATG26b</i>-deficient mutants exhibited significantly reduced virulence on litchi fruits and leaves. Collectively, our findings demonstrate that PlAtg26b plays a pivotal role in the biological development and pathogenicity of <i>P. litchii</i>.