# Investigating the Biocontrol and Plant Growth-Promoting Potential of Pseudomonas yamanorum for Sustainable Management of Tomato Early Blight (Alternaria alternata)

## TL;DR

This study explores how Pseudomonas yamanorum can help control tomato early blight and improve plant growth.

## Contribution

The study identifies Pseudomonas yamanorum as a novel biocontrol agent effective against Alternaria alternata in tomato plants.

## Key findings

- Pseudomonas yamanorum reduced A. alternata mycelial growth by 68.7% and spore germination by 88.7% in vitro.
- Treated plants showed increased disease resistance and improved growth metrics like shoot length and biochemical activity.
- P. yamanorum maintained fruit quality parameters such as firmness and sugar content while reducing stress markers.

## Abstract

Tomato (Solanum lycopersicum L.) is among the most economically significant and nutritionally valuable vegetable crops grown globally. However, fungal diseases such as Early Blight caused by Alternaria alternata are a major factor limiting yield and fruit quality in tomato production. This study investigates the biocontrol potential of locally isolated rhizobacterium Pseudomonas yamanorum against A. alternata, the causal agent of early blight in tomato, under both in vitro and in planta conditions. In vitro assays demonstrated significant antifungal activity; in the dual confrontation assay, P. yamanorum (108 CFU/mL) reduced A. alternata mycelial growth by 68.7%, while spore germination was inhibited by 88.7%. In planta trials demonstrated that plants treated with P. yamanorum (107 CFU/mL) alone exhibited the lowest disease severity (2.5). The treatments also significantly enhanced plant growth, with shoot length reaching 45 cm versus 26 cm in infected controls. Biochemical analyses revealed increased catalase (94.84 units mg−1 protein min−1), peroxidase (5.83), and ascorbate peroxidase (67.01) activities in treated plants. Total polyphenol and protein contents also increased (0.81 mg/g and 15.82 mg/g, respectively). Furthermore, P. yamanorum treatments maintained fruit quality parameters such as firmness (3.13), sugar content (6.43 °Brix), and juice yield (55.88%), while reducing malondialdehyde (2.02 µmol/g Dry Weight) and electrical conductivity (0.59 mS/cm). These findings highlight P. yamanorum as a promising biocontrol agent and plant growth-promoting bacteria that improve disease resistance, which can be combined with salicylic acid to further enhance crop vigor and fruit quality under biotic stress.