# A novel internal reference microorganism-based method reveals wild-enriched Penicillium for enhancing growth and disease resistance in Fritillaria thunbergii

## TL;DR

A new method identifies beneficial wild microbes, like Penicillium, that help Fritillaria thunbergii grow better and resist disease.

## Contribution

A novel IRM-based method (IRMRADMA) is developed to accurately analyze microorganism abundance in plant rhizospheres.

## Key findings

- Clavatospora was identified as a host-specific internal reference microorganism.
- Wild F. thunbergii rhizospheres contain more beneficial Penicillium strains than cultivated ones.
- Penicillium strains promote plant growth and suppress disease through multiple mechanisms.

## Abstract

Fritillaria thunbergii Miq. is an important traditional Chinese medicinal herb, but bulb rot disease causes severe losses during its cultivation. Screening and reintroducing beneficial microorganisms from the wild rhizosphere is an effective strategy to increase disease resistance in cultivated plants. However, the absolute quantitative characteristics of microorganisms cannot be reflected by traditional methods based on relative abundance analysis due to compositional bias.

In this study, we identified Clavatospora as a host-specific internal reference microorganism (IRM) and established an IRM-based relative abundance differential microorganism analysis (IRMRADMA) method.

Application of this method revealed that wild F. thunbergii possesses greater potential than cultivated plants for mining beneficial rhizosphere microorganisms. Specifically, Penicillium was identified as a key wild-enriched genus. Subsequently, two strains, Penicillium korosum and Penicillium aculeatum, were isolated from the rhizosphere of wild F. thunbergii. Functional tests confirmed that these strains demonstrated dual functions in disease suppression and plant growth promotion by solubilizing phosphate, producing siderophores, antagonizing pathogens, and upregulating defenserelated genes.

This study established the IRM-RADMA method and identified key Penicillium strains from the wild Fritillaria thunbergii rhizosphere. Their confirmed dual functions in growth promotion and disease suppression validate the ‘plant microbiome rewilding’ strategy, offering a new paradigm for the biological control of F. thunbergii diseases.