Wheat blast, caused by the fungus Magnaporthe oryzae pathotype Triticum is a fast-acting and devastating disease of the crop in the tropical producing areas of Brazil. The pathogen attacks the wheat leaves; however, the most severe damage occurs at the spikes, causing up to 100% loss when environmental conditions are favorable and the genotype is susceptible.

The major resistance gene for wheat head blast comes from the 2NS chromosomal segment, introgressed from Aegilops ventricosa. Chemical control measures have shown limited effectiveness in managing the disease. GDM, a private global multi-crop breeding company, operates three main wheat breeding programs in Brazil: Rio Grande do Sul, Paraná, and the tropical Cerrados region, where blast resistance improvement is a critical objective.

The aim of this study is to show and discuss the results of a middle-term effort on the increase of the genetic resistance of GDM’s wheat germplasm to wheat head blast. Two main selection strategies were applied: i) extensive phenotyping in controlled conditions; and ii) selection for the 2NS chromosomal segment through marker assisted selection, both complementing the field selection. Every year all lines which advance from nursery to first year field trials, pass through both selection strategies, being approximately one thousand lines per year.

As a result, the frequency of the 2NS segment has increased over the last five years, in all three GDM’s wheat breeding programs in Brazil, diagnosed in the lines in third year field trial. For the Cerrados program, the frequency of the segment has increased from 81%, in 2020, to 100%, in 2024 (R2=0.75), comparing to from 78% to 95% (R2=0.65) in Rio Grande do Sul and from 80% to 95% (R2=0.40) in the Paraná program.

The general mean of the Area Under the Disease Progress Curve (AUDPC) in controlled conditions from 2021 to 2023 (data from 2024 is not available at the date of this study), was taken as a measure of the success of the strategies described.

The AUDPC average has diminished from 450 in 2021 to 150 in 2023, which represents a three-times decrease in a curse of three years. As a conclusion, phenotyping in controlled conditions and selection for the 2NS segment resulted in important improvement in wheat blast resistance in GDM’s Cerrados’ germplasm.