Optimizing the application of a Metarhizium brunneum strain to mitigate iron deficiency in tomato plants

Abstract: Metarhizium brunneum (strain EAMa 01/58-Su) not only acts as a biological control agent but also contributes to improved plant nutrition, alleviating symptoms of iron (Fe) deficiency and contributing to plant growth promotion. This study aims to optimize its role as plant growth promoter, through the application method, and to uncover the molecular
mechanisms involved in Fe deficiency responses in tomato plants (Strategy I). For this aim,
plants were inoculated with M. brunneum using three methods: root immersion (RI), foliar
spraying (FS), and seed dressing (SD). Chlorophyll content (SPAD), ferric reductase activity
(FRA), and expression of Fe-related genes (SlFER and SlIRT1) were measured by qRT-PCR.
Results showed that RI and SD increased FRA and gene expression, with a 20 % increase in
total plant fresh weight when the SD method was applied. This work highlights the potential of M. brunneum as a biostimulant and growth promoter.