# “Secreted in Xylem” Genes (SIX Genes): Relationship to the Aggressiveness of Fusarium oxysporum f. sp. albedinis

## TL;DR

This study explores how certain genes in a fungus that causes a deadly disease in date palms are linked to how aggressive the fungus is.

## Contribution

The study is the first to show a correlation between the number and type of SIX genes and the aggressiveness of Fusarium oxysporum f. sp. albedinis.

## Key findings

- Highly aggressive Foa isolates had 9–12 SIX genes, while less aggressive ones had 0–6.
- SIX12 and SIX13 were present in all aggressive isolates, suggesting a role in virulence.
- There is a positive correlation between SIX gene count and pathogenicity in Foa isolates.

## Abstract

Fusarium oxysporum f. sp. Albedinis (Foa) is the causal agent of Bayoud disease, responsible for the loss of 75% of date palm trees in Morocco and posing a threat to its cultivation across North Africa. This study examined ten Foa isolated from various Moroccan locations for the presence of the transposable element Fot1 and the distribution of “Secreted in Xylem” (SIX) genes. Pathogenicity assays on date palm seedlings revealed varying levels of aggressiveness among isolates, with a positive correlation between aggressiveness and SIX gene count. Highly aggressive isolates harbored 9–12 SIX genes, while hypo-aggressive and moderately aggressive isolates carried 0–6. SIX2, SIX6, SIX7, SIX11, SIX12, and SIX13 were differently dispersed among aggressive isolates, whereas SIX12 and SIX13 were present in all aggressive isolates, suggesting their potential role in virulence. This study is the first to highlight a correlation between Foa aggressiveness and SIX gene distribution, providing a foundation for future functional analyses to elucidate their role in pathogenicity.