Mildew locus o (MLO) is a plant-specific gene family.
Specific members of the Mildew Locus O gene family act as powdery mildew susceptibility factors.
Their inactivation, as the result of a loss-of-function mutation, gene knock-out, or knock-down, is associated with a peculiar form of resistance, referred to as mlo resistance.
[1] [2] The mlo gene family is widely conserved across the plant kingdom with some members evolving as early as the first land plants.
[1] TaMLO genes are the MLOs in bread wheat, Triticum aestivum.