The use of beneficial microorganisms offers a sustainable alternative to chemical fungicides for managing plant diseases. This study aimed to investigate the biocontrol potential and underlying mechanisms of Serratia marcescens (YNAU-SM-1) for controlling potato late blight caused by Phytophthora infestans. Dual culture assay, fluorescent dye staining, spore germination inhibition assays, in vitro bioassays, greenhouse experiments, and biochemical analyses of defense-related enzymes and osmotic regulators were conducted to determine the effects of YNAU-SM-1 using P. infestans HJG02 as a target pathogen. Dual culture assays revealed that YNAU-SM-1 significantly inhibited the mycelial growth of P. infestans HJG02 by 70.26%. Abnormal hyphal expansion and excessive branching were also observed under microscopic observations. Fluorescent dye staining revealed that YNAU-SM-1 induced intracellular accumulation of reactive oxygen species (ROS) in P. infestans HJG02, leading to sporangial inactivation. Spore germination inhibition assays suggested the bacterial strain strongly inhibited sporangial direct germination (98.86%), zoospore release (70.13%), and cystospore germination (100%). Detached leaf, tuber slice, and greenhouse assays confirmed the efficacy of YNAU-SM-1, with disease control efficiencies of 67.62%, 65.48%, and 71.04% under preventive, simultaneous, and curative treatments, respectively. Biochemical analyses indicated that YNAU-SM-1 increased soluble protein and reduced malondialdehyde (MDA) content, and altered the general trend of peroxidase (POD), and soluble sugar content in potato leaves. These findings suggest that YNAU-SM-1 suppresses P. infestans HJG02 through both direct antagonism and the induction of host defenses, highlighting its potential as an effective biocontrol agent for managing potato late blight.

This research investigates how fourth-instar larvae of the potato tuber moth, Phthorimaea operculella, respond to plant secondary metabolites (sucrose, glucose, nicotine, and tannic acid) both in terms of gustatory electrophysiology and feeding behavior. The objective is to establish a theoretical foundation for employing plant-derived compounds in potato tuber moth control. We employed single-sensillum recording techniques and dual-choice leaf disk assays to assess the gustatory electrophysiological responses and feeding preferences of these larvae towards the mentioned compounds. Sensory neurons responsive to sucrose, glucose, nicotine, and tannic acid were identified in the larvae’s medial and lateral sensilla styloconica. Neuronal activity was influenced by stimulus type and concentration. Notably, the two types of sensilla styloconica displayed distinct response patterns for sucrose and glucose while they had similar firing patterns towards nicotine and tannic acid. Sucrose and glucose significantly promoted larval feeding, while nicotine and tannic acid had significant inhibitory effects. These findings demonstrate that the medial and lateral sensilla styloconica house sensory neurons sensitive to both feeding stimulants and inhibitors, albeit with differing response profiles and sensitivities. This study suggests that sucrose and glucose are promising candidates for feeding stimulants, while nicotine and tannic acid show potential as effective feeding inhibitors of P. operculella larvae.

Soilborne pathogens significantly impact potato productivity by altering rhizosphere enzymatic activities and microbial communities. Pathogen-induced changes in enzyme activities are correlated with shifts in microbial community composition, but causal relationships remain unclear. This study investigates the effects of five key pathogens—Phytophthora infestans, Streptomyces scabies, Spongospora subterranea, Ralstonia solanacearum and Globodera rostochiensis—on soil enzyme activities and microbial community structure in potato rhizosphere soils under continuous cropping. This experiment involved pathogen inoculation and soil sampling in potato rhizosphere soils, with treatments replicated three times. Potatoes were planted on March 22, 2023, and harvested on August 25, 2023. Enzymatic activities were measured at different growth stages, and microbial communities were analyzed using high-throughput sequencing. Pathogen-induced variations in enzymatic activities were observed, potentially promoting disease proliferation. For instance, under S. scabies stress, urease (URE) activity increased significantly at the full flowering and post-flowering stages, while catalase (CAT) activity decreased significantly during the seedling and full flowering stages. Under S. subterranea stress, activities of urease, sucrase (SUC), and alkaline phosphatase (ALP) decreased. M. nematode stress led to a decline in URE and sucrase activities. P. infestans infection led to a decrease in URE activity at the sowing stage. Furthermore, microbial community composition was significantly correlated with disease incidence, with specific taxa such as Planctomycetes and Basidiomycota showing negative correlations with S. subterranea incidence, while Candidatus Dormibacteraeota and Ascomycota were positively associated with P. infestans. These results suggest that pathogen-induced changes in enzymatic activities play a critical role in disease dynamics and microbial interactions. The findings highlight the importance of understanding the effects of soilborne pathogens on soil enzyme activities and microbial communities, providing insights into disease management strategies in potato farming.