Gansu researchers' five-strain consortium controls onion basal rot with 73.3% efficacy in pot tests

A team led by Xueping Li at the Institute of Plant Protection, Gansu Academy of Agricultural Sciences, built a consortium of five microbial strains that suppressed onion basal rot and reduced soil salinity and alkalinity in pot experiments, EurekAlert reports. The results were published in Microbiology China on 20 October 2026. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗ According to the authors, onion yield and quality in China are threatened by soil salinization and by basal rot outbreaks linked to intensive farming and continuous cropping.

Strain selection and compatibility

From the rhizosphere of diseased onion plants in Jingtai County, Gansu Province, the researchers isolated 20 salt- and alkali-degrading strains. Two of them, LAB2 and LAB3.2, tolerated both 10% NaCl and pH 10.0. In liquid culture, LAB3.2, LAB2 and MX38 lowered alkalinity by 12.3–17.6%, while SYP202, LAB2, MFL22 and MX50 reduced salt content by 10.61–19.26% after 72 hours. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

The most promising isolates were then combined with biocontrol and plant-growth-promoting strains from the team's culture collection for specialty crops in Gansu. Plate confrontation assays were used to check that no member antagonized another. Of three candidate consortia, the one designated A3 performed best: it released 99.13 mg/L of potassium, fixed 0.225 g/L of nitrogen, produced 39.54 siderophore units and 10.66 mg/L of indole-3-acetic acid, and inhibited Fusarium oxysporum, the dominant basal rot pathogen, by 95.15%. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

Composition and pot results

Consortium A3 comprises Staphylococcus sciuri LAB2, Exiguobacterium acetylicum LAB3.2, Bacillus velezensis MP6, B. halotolerans SYP202 and Trichoderma harzianum M3. An orthogonal design set the optimal ratio of M3 : LAB3.2 : LAB2 : MP6 : SYP202 at 9 : 9 : 3 : 7 : 5. The consortium was ultimately designated "Tuweiwei No. 9". eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

In pot experiments, onion seedlings were inoculated with the pathogen and then treated with A3. Control efficacy against basal rot was 73.3%. Soil pH fell by 0.5 units and soluble salt concentration dropped by 44.46 mS/cm. Treated plants were taller, with thicker stems and longer roots than untreated controls. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

The authors note that the results come from a single cultivar and a single pathogen isolate under controlled conditions. Performance under variable field salinity, native microbial communities and real irrigation regimes remains to be tested. The team is studying how the consortium changes the rhizosphere microbiome and soil nutrient status over a full growing season, and is working on a stable, scalable fermentation process for regional biofertilizer production. Li said that compatibility between strains, not only their individual performance, proved decisive in the final formulation.