I n agricultural ecosystI n agricultural ecosystems, continuous monoculture frequently leads to increased  disease severity, a phenomenon closely associated with crop genetic uniformity and  disruptions in the soil microbial community (1). Root exudates play a crucial role in the rhizosphere ecosystem. On the one hand,  root exudates supply abundant carbon and nitrogen sources, as well as energy  substrates, thereby attracting and supporting the aggregation and proliferation of  microorganisms in the rhizosphere (2–4). Besides, the composition and content of root  exudates differ substantially among crop species, determining their specific attractiveness and selectivity for distinct microbes. For example, the root exudates of certain  plants are enriched with specific sugars and amino acids, which facilitate the targeted  recruitment of nitrogen-fixing bacteria, phosphate-solubilizing bacteria, or beneficial microbes that secrete plant hormones, thereby promoting their dominance within the  rhizosphere microbial community (5–7). On the other hand, some secondary metabolites in root exudates possess inherent antimicrobial, bacteriostatic, or allelopathic  properties, inhibiting the growth and proliferation of certain harmful microorganisms,  thereby contributing to the regulation of rhizosphere microbial community balance  and supporting the maintenance of healthy plant growth (8–10). Phenolic acid-like  compounds secreted by the root system of wheat promote the inter-root colonization of  Streptomyces spp. in pea and bolster resistance to pea wilt disease caused by Fusarium  oxysporum spp. (11). Sulfur-containing compounds secreted by the root system of garlic  promote the colonization of Bacillus spp. in the inter-root of peppers and inhibit the  greening disease induced by Ralstonia solanacearum spp. (12). Furthermore, thioglucosides secreted by the root system of oilseed rape promote the proliferation of Actinobacillus actinomycetemcomitans and suppress Rhizoctonia spp. induced root rot in chickpea  (13). These metabolites play crucial roles in enhancing plant immune responses and  improving disease resistance. Crucially, such beneficial interactions mediated by root  exudates are also evident in intercropping systems involving pepper (Capsicum annuum).  For instance, pepper benefits from intercropping with rosemary through reduced pest  pressures (14), while in a maize-pepper system, soil-borne disease suppression occurs via  plant-plant-microbe mechanisms (15). These findings solidly establish pepper as both a  recipient and a potential contributor in interspecific interactions. However, the specific role of pepper root exudates in enhancing the soil-borne disease resistance of snap  beans remains unexplored. Phaseolus vulgaris L. (snap bean) root rot limits yields wherever the crop is grown  and constitutes a major constraint to dry edible and snap bean production worldwide  (16). Reported root rot caused by Fusarium solani in the United States could cause yield  losses of up to 84%. Reported yield losses from bean root rot complex are even more  devastating in the developing world. Disease pressure is likely worse in developing  countries because of higher abiotic stress. As a result of increased stress, bean root  rot complex has been attributed to yield losses of up to 100% in Uganda and up  to 70% in Rwanda (17). Cultural and chemical disease control methods are of limited  value against root rots. Seed or soil treatments with selective fungicides, crop rotations,  cover crops, seedbed preparations, and other measures have, in some cases, improved  yield in the presence of Aphanomyces euteiches and F. solani root rot disease. However,  few of these measures have proven consistently economical or effective against root  rot (18). For the purpose of investigating the disease-suppressive effect of Capsicum  annuum L. (pepper) root exudates on snap bean root rot and its microbiological  mechanisms, root application of exogenous pepper root exudates was employed in  this study to simulate their potential role within a natural intercropping system. The  aim was to investigate whether the application of pepper root exudates alone could  effectively mitigate root rot infection in snap beans by modulating the rhizosphere  microbial community to recruit beneficial microorganisms, particularly those with plant  disease-suppressive capabilities, and thereby effectively alleviate snap 

I n agricultural ecosystI n agricultural ecosystems, continuous monoculture frequently leads to increased  disease severity, a phenomenon closely associated with crop genetic uniformity and  disruptions in the soil microbial community (1). Root exudates play a crucial role in the rhizosphere ecosystem. On the one hand,  root exudates supply abundant carbon and nitrogen sources, as well as energy  substrates, thereby attracting and supporting the aggregation and proliferation of  microorganisms in the rhizosphere (2–4). Besides, the composition and content of root  exudates differ substantially among crop species, determining their specific attractiveness and selectivity for distinct microbes. For example, the root exudates of certain  plants are enriched with specific sugars and amino acids, which facilitate the targeted  recruitment of nitrogen-fixing bacteria, phosphate-solubilizing bacteria, or beneficial microbes that secrete plant hormones, thereby promoting their dominance within the  rhizosphere microbial community (5–7). On the other hand, some secondary metabolites in root exudates possess inherent antimicrobial, bacteriostatic, or allelopathic  properties, inhibiting the growth and proliferation of certain harmful microorganisms,  thereby contributing to the regulation of rhizosphere microbial community balance  and supporting the maintenance of healthy plant growth (8–10). Phenolic acid-like  compounds secreted by the root system of wheat promote the inter-root colonization of  Streptomyces spp. in pea and bolster resistance to pea wilt disease caused by Fusarium  oxysporum spp. (11). Sulfur-containing compounds secreted by the root system of garlic  promote the colonization of Bacillus spp. in the inter-root of peppers and inhibit the  greening disease induced by Ralstonia solanacearum spp. (12). Furthermore, thioglucosides secreted by the root system of oilseed rape promote the proliferation of Actinobacillus actinomycetemcomitans and suppress Rhizoctonia spp. induced root rot in chickpea  (13). These metabolites play crucial roles in enhancing plant immune responses and  improving disease resistance. Crucially, such beneficial interactions mediated by root  exudates are also evident in intercropping systems involving pepper (Capsicum annuum).  For instance, pepper benefits from intercropping with rosemary through reduced pest  pressures (14), while in a maize-pepper system, soil-borne disease suppression occurs via  plant-plant-microbe mechanisms (15). These findings solidly establish pepper as both a  recipient and a potential contributor in interspecific interactions. However, the specific role of pepper root exudates in enhancing the soil-borne disease resistance of snap  beans remains unexplored. Phaseolus vulgaris L. (snap bean) root rot limits yields wherever the crop is grown  and constitutes a major constraint to dry edible and snap bean production worldwide  (16). Reported root rot caused by Fusarium solani in the United States could cause yield  losses of up to 84%. Reported yield losses from bean root rot complex are even more  devastating in the developing world. Disease pressure is likely worse in developing  countries because of higher abiotic stress. As a result of increased stress, bean root  rot complex has been attributed to yield losses of up to 100% in Uganda and up  to 70% in Rwanda (17). Cultural and chemical disease control methods are of limited  value against root rots. Seed or soil treatments with selective fungicides, crop rotations,  cover crops, seedbed preparations, and other measures have, in some cases, improved  yield in the presence of Aphanomyces euteiches and F. solani root rot disease. However,  few of these measures have proven consistently economical or effective against root  rot (18). For the purpose of investigating the disease-suppressive effect of Capsicum  annuum L. (pepper) root exudates on snap bean root rot and its microbiological  mechanisms, root application of exogenous pepper root exudates was employed in  this study to simulate their potential role within a natural intercropping system. The  aim was to investigate whether the application of pepper root exudates alone could  effectively mitigate root rot infection in snap beans by modulating the rhizosphere  microbial community to recruit beneficial microorganisms, particularly those with plant  disease-suppressive capabilities, and thereby effectively alleviate snap