Why is the Sm1 gene likely to break down?
The Sm1 gene does not change or “break down”. However, the Sm1 gene is single gene insect resistance, which has a history of becoming ineffective over time as insect populations change. Since a small number of midge carry a mutation allowing them to attack varieties carrying the Sm1 gene and survive (referred to as virulent midge), these can mate with other virulent midge and quickly build up a large population that can feed on wheat varieties with the Sm1 gene. The objective of the interspersed refuge is to slow down the potential shift in the midge population towards the virulent biotype.
