A group from National Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Shandong, China has reported on Bacillus amyloliquefaciens QSB-6 strain isolated from apple orchard soils and its effect on apple tree roots and disease.
https://www.frontiersin.org/articles/10.3389/fmicb.2021.746799/full
Authors compared effects of 4 types of soils on apple tree roots.
- untreated soil from a 31-year-old orchard (CK1)
- the same soil fumigated with methyl bromide (CK2)
- the same soil treated with the manure carrier only (T1)
- the same soil treated with Bacillus amyloliquefaciens strain QSB-6 manure treatment (T2)
Interestingly, the CK2, T2, and T1 treatments significantly promoted the growth of apple tree roots, and the relative treatment effects were ranked from high to low: CK2 > T2 > T1 > CK1.
The number of rhizobacteria increased significantly after T2 treatment by 9.64 times higher in T2 than in CK1, and soil fungal numbers were reduced significantly by 85.58% (in CK2) and 81.74% (in T2) compared with CK1.
Extracellular metabolites from strain QSB-6 showed a strong inhibitory effect on Fusarium hyphal growth and spore germination as shown below.
(A) Fusarium proliferatum, (B) Fusarium solani, (C) Fusarium verticillioides, (D) Fusarium oxysporum
In summary, B. amyloliquefaciens QSB-6 has a good inhibitory effect on Fusarium in the soil and can significantly promote apple tree root growth. It has great potential as a biological control agent against apple disease.