Mechanisms of <i>Burkholderia arboris</i> M13 in Combating Bacterial Diseases of Horticultural Crops and Facilitating Plant Growth

Bacterial diseases pose a serious threat to horticultural crops, necessitating the exploration of biocontrol resources for sustainable agricultural development. This study characterises Burkholderia arboris M13, a novel biocontrol strain exhibiting broad-spectrum antagonism in vitro against major phytopathogenic bacteria of horticultural crops, including Pseudomonas syringae pv. tomato, Ralstonia solanacearum, Paracidovorax citrulli, and Xanthomonas campestris pv. campestris. Applications of its bacterial suspension or culture supernatant significantly suppressed tomato bacterial speck, bacterial wilt, watermelon bacterial fruit blotch, and cabbage black rot in greenhouse and field trials. The strain also induced plant systemic resistance and promoted plant growth. Genomic analysis revealed significant novelty, as B. arboris M13 possesses two unique plasmids and harbours 20 biosynthetic gene clusters for secondary metabolites, with several showing weak collinearity to close relatives, indicating genetic determinants for its expanded functionality. Furthermore, B. arboris M13 demonstrated compatibility with the plant growth regulator (24-epibrassinolide) but incompatibility with the copper-based bactericide copper hydroxide, which enhances its practical integration into existing crop management strategies. This combination of effective biocontrol, plant growth promotion, distinct genomic features, and chemical compatibility establishes B. arboris M13 as a versatile and promising candidate for sustainable agriculture.