Genomic insights into the biocontrol and plant growth-promoting activities of the endophytic bacterium Burkholderia diffusa nsu-26 from Trichosanthes kirilowii fruit.

Abstract

Trichosanthes kirilowii Maxim., a medicinal and edible plant widely cultivated in China, is threatened by anthracnose caused by Colletotrichum gloeosporioides, and long-term reliance on chemical fungicides has driven the need for sustainable biocontrol alternatives. Here, we evaluated the biocontrol and plant growth-promoting potential of nsu-26, an endophytic bacterium isolated from T. kirilowii fruits. Strain nsu-26 effectively suppressed C. gloeosporioides NFD-5 mycelial growth, achieving a control efficiency of 91.44% on detached fruits and 84.39% on leaves, while also exhibiting phosphate-solubilizing, potential nitrogen-fixing, siderophore-producing, cellulase-producing, and indole-3-acetic acid producing activities. In vivo experiments confirmed that strain nsu-26 significantly increased the seed germination energy, germination rate, as well as plant height and root length of T. kirilowii seedlings. Through phenotypic, physio-biochemical, and phylogenomic analyses, strain nsu-26 was identified as Burkholderia diffusa. Genome-based screening revealed no high-risk acquired resistance genes, and hemolytic tests and tissue-cultured seedling experiments indicated no detectable pathogenicity under the tested conditions. Whole-genome sequencing revealed a 7.07-Mb genome comprising two circular chromosomes and two plasmids, harboring 30 putative biosynthesis-related gene clusters, including those for siderophore and indole-3-acetic acid biosynthesis, which may contribute to the observed biocontrol and growth-promoting activities. Collectively, these findings indicate that B. diffusa nsu-26 is a promising biocontrol agent for the sustainable management of anthracnose in T. kirilowii.

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