Apple replant disease (ARD) is mainly caused by biological factors, and it severely restricts the development of the apple industry.  The use of biological control measures to alleviate ARD is critically important for the sustainable development of the apple industry.  The effects of raw amino acid powder and Trichoderma harzianum fertilizer on plant biomass, leaf and root indexes, soil physical and chemical properties, soil enzyme activities, and the soil fungal community were studied under pot and field conditions using Malus hupehensis Rehd. seedlings and grafted trees (Fuji New 2001/M9T337) as experimental materials.  We found that the application of the materials significantly promoted plant growth, increased the leaf photosynthesis and chlorophyll content, root respiration rate, root antioxidant enzyme activities, and soil enzyme activities, significantly reduced the number of Fusarium sp. in soil, and significantly increased the abundance of beneficial fungi.  In conclusion, the mixed application of raw amino acid powder and T. harzianum fertilizer is an effective method for the prevention and management of ARD.

Litchi downy blight, caused by the plant pathogenic oomycete Peronophythora litchii, is one of the most devastating diseases on litchi and resulted in huge economic losses.  Autophagy plays an essential role in the development and pathogenicity of the filamentous fungi.  However, the function of autophagy in oomycetes remain elusive.  Here, an autophagy-related protein Atg3 homolog PlAtg3 was identified and characterized in P. litchii.  The absence of PlATG3 through the CRISPR/Cas9 gene replacement strategy compromised vegetative growth and sexual/asexual development.  Cytological analyses revealed that the deletion of PlATG3 impaired autophagosome formation with monodansylcadaverine (MDC) staining and significantly disrupted zoospore release due to defects of sporangial cleavage with FM4-64 staining.  Atg8 is considered to be an autophagy marker protein in various species.  Western blot analysis indicated that PlAtg3 is involved in degradation of PlAtg8-PE.  Interestingly, PlAtg3 was unable to interact with PlAtg8 in yeast two hybrid (Y2H) assays, possibly due to the absence of the Atg8 family interacting motif (AIM) in PlAtg3.  Furthermore, pathogenicity assays revealed that the deletion of PlATG3 considerably reduced the virulence of P. litchii.  Taken together, our data reveal that PlAtg3 plays an important role in radial growth, asexual/sexual development, sporangial cleavage and zoospore release, autophagosome formation, and pathogenicity in P. litchii.  This study contributes to a better understanding of the pathogenicity mechanisms of P. litchii and provides insights for the development of more effective strategies to control oomycete diseases.