Background: Weeds in farmland seriously threaten crop yield and cause huge economic losses. Due to the extensive use of chemical herbicides, a series of problems have been arisen, such as environmental pollution, soil degradation and pesticide residues. To assess the herbicidal activity, crop safety, taxonomic identity and infection process of strain HZ-011, the methods of inoculation on detached leaves in vitro and pot plants in vivo, as well as scanning electron microscopy, were used in this study. Results: The results indicated that strain HZ-011 had pathogenic effects on detached leaves of four weeds, including Amaranthus retroflexus Linn., Elsholtzia densa Benth., Malva crispa Linn. and Chenopodium album Linn. in vitro. Strain HZ-011 also showed high pathogenicity to C. album and A. retroflexus in vivo, in which the pathogenicity rates were 100%, meaning all plants died after 7 days in the pot test, while the pathogenicity rates for E. splendens and M. crispa were 60.00 and 29.60%, respectively. This strain was safe for local crops, including Vicia faba Linn., Pisum sativum Linn., Brassica napus Linn., Hordeum vulgare Linn. and Triticum aestivum Linn. Strain HZ-011 was identified as the fungus Botrytis euroamericana based on its morphology, molecular biology and a constructed phylogenetic tree. The infection process of B. euroamericana HZ-011 in C. album was studied by plant histopathological observations after pathogen infection. This procedure showed that the mycelium of strain HZ-011 invaded C. album tissues from the stomata, infected and propagated within the tissues, and the spores produced further damage in the C. album tissues and lesions occurred on the surfaces of C. album leaves. Conclusion: These tests provide a basis for fungus B. euroamericana HZ-011 as a potential microbial herbicide.

Trichoderma polysporum (Link) Rifai HZ-31 fermentation broth was separated and purified by extraction, column chromatography, and high-performance liquid chromatography. Four monomer compounds with strong herbicidal activity were obtained: p-hydroxyphenyl-2,3-dihydroxypropyl ether, o-hydroxy-3-carbonyl-1-phenylpropanol, 1,8-propanediol o-xylene, and 2-3-dihydroxypropyl propionate. The biological activity verification test indicated that the four monomer compounds could inhibit the germination of wild oat (Avena fatua L.) and canola (Brassica napus L.) seeds. Of the four, compound 3 (1,8-propanediol o-xylene) had obvious inhibitory effects on the germination of A. fatua and B. napus seeds, with inhibition rates of 83.33% and 86.67%, respectively. Therefore, the identification of this monomer compound lays a foundation for the further development of a novel microbial herbicide by directly utilizing it and developing new derivatives with herbicidal functions as lead compounds.

Potato blackleg disease is caused by Pectobacterium atrosepticum, can seriously destroy potatoes’ growth and development. To accurately evaluate the expression levels of genes involved in potato (Solanum tuberosum) responses to P. atrosepticum infection, seven candidate reference genes (EF1α, eIF5A3, Tubulin, Ubiquitin, GAPDH, Actin, and CYP3) were systematically assessed for their expression stability at 1, 3, and 5 days after inoculation (dai) using the geNorm, NormFinder, BestKeeper, ∆Ct, and RefFinder algorithms. The results demonstrated that EF1α exhibited the highest stability among all experimental conditions, followed by eIF5A3 and Tubulin, whereas Ubiquitin displayed the least stability. To validate the screening outcomes, the expression patterns of four disease resistance-related genes (RBOHC, WRKY24, MPK3, and CPK32) were analyzed in both resistant and susceptible potato cultivars using the EF1α as the most stable and Ubiquitin as the least stable. Validation experiments revealed that the expression levels of disease resistance-related genes were stable and consistent with the RNA-Seq data when EF1α was used as a reference gene. In contrast, using Ubiquitin as a reference gene led to significant variability. Therefore, EF1α can be employed as the reference gene when studying the interaction between the potato and P. atrosepticum, providing a standardized reference for the subsequent studies on screening of disease resistance genes and exploring of disease resistance mechanism in potato.

The herbicidal efficacy and crop safety of Fusarium acuminatum strain HL-29, an endophytic fungus isolated from infected Amaranthus retroflexus in Qinghai Province, were evaluated. In vitro leaf assays demonstrated its pathogenicity against four broadleaf weeds, with efficacy ranked as follows: Elsholtzia densa = Senecio vulgaris = Chenopodium album > Malva verticillata. Pot trials further confirmed that the HL-29 fermentate caused 100% disease incidence in S. vulgaris, C. album, and E. densa. Notably, the strain showed no pathogenicity toward seven major local crops, indicating excellent selectivity. Scanning electron microscopy (SEM) revealed key morphological changes during the infection process on C. album leaves. These results establish F. acuminatum HL-29 as a promising biocontrol candidate against broadleaf weeds in the Qinghai–Tibet Plateau, providing a theoretical foundation for developing alpine-adapted mycoherbicides.

In screening for biocontrol strains with broad-spectrum and efficient herbicidal activity, strain GD-011 isolated from naturally susceptible M. sativa (Medicago sativa L.) roots was selected as a promising candidate. The control effects of strain GD-011 on nine weeds of Qinghai farmland were evaluated in vitro and in vivo, and its safety to five local crops was tested. The in vivo spray inoculation test showed that strain GD-011 had a strong pathogenic effect on the weeds M. verticillata (Malva verticillata L.), E. densa (Elsholtzia densa Benth), and A. fatua (Avena fatua L.), with incidence rates of more than 80.87% and fresh weight control effects of more than 71.8%. Crop safety tests showed that the B. napus (Brassica napus L.) crop is moderately susceptible to strain GD-011, with slight reactions in H. vulgare (Hordeum vulgare L.), but strain GD-011 is safe for T. aestivum (Triticum aestivum L.), P. sativum (Pisum sativum L.), and V. faba (Vicia faba L.) Observations on the morphological characteristics combined with a sequence analysis of the ribose rDNA internal transcribed spacer (rDNA ITS), the Elongation factor (EF-1α) gene, and the antigen-related protein gene (Alt a1) identified strain GD-011 as Alternaria gaisen. Scanning electron microscopy observations showed that the mycelia of strain GD-011 invaded the leaf tissue through the stomata on the surface, with the formation of a parasitic mycelium network on the surface of the tissue, the metabolism of E. densa leaf tissues was disturbed, and leaf tissues appeared to be broken. From the perspective of its herbicidal potential, the metabolites of strain GD-011 have good control effects on most weeds and are relatively safe for crops.