Isolation, identification and herbicidal potential of weed pathogenic strain HL-12

The development of microbial herbicides in the alpine ecological zone of the Qinghai-Tibet Plateau remains largely unexplored. This study isolated strain HL-12 from naturally infected Setaria viridis leaves and evaluated its herbicidal potential. The taxonomic status of HL-12 was determined through morphological characteristics and multi-locus (ITS, 28S rDNA-LSU, and TEF1-α) phylogenetic analysis. Its herbicidal potential was assessed against four dominant broadleaf weeds in the Qinghai-Tibet Plateau (Chenopodium album, Elsholtzia densa, Malva verticillata, and Senecio vulgaris) using detached leaf and pot experiments. Safety evaluations were conducted on six major crops and three cold-tolerant vegetables in Qinghai Province. Scanning Electron Microscopy (SEM) was employed to observe the infection mechanisms, and nutritional optimisation experiments identified the optimal carbon and nitrogen sources. HL-12 was identified as Bipolaris sivanesaniana. Seven days post-inoculation, disease incidence rates in potted plants of the four species listed above reached 90.48%, 90%, 100%, and 100%, respectively. Regarding crop safety, HL-12 was safe for Triticum aestivum and Solanum melongena but unsafe for Hordeum vulgare, Zea mays, Brassica napus, Cucumis sativus, Solanum lycopersicum, Vicia faba, and Pisum sativum. The hyphae of HL-12 invaded S. vulgaris leaves through stomata and wounds. Corn meal and soybean meal were identified as the optimal carbon and nitrogen sources, respectively, as they yielded superior mycelial growth and spore production. Strain HL-12 demonstrates good potential as a bioherbicide agent in alpine regions. Further optimisation of culture parameters, formulation development, and field efficacy evaluation are warranted.