Erosion of Quantitative Resistance in Wheat and Barley to fusarium Head Blight: Gene Pyramiding Achieves and Durability Study

Fusarium head blight (FHB), caused by several fusarium species, is one of the diseases causing the greatest worldwide damage to small grain cereals, especially wheat and barley. FHB outbreaks can substantially diminish grain yield and end-use quality due to sterile florets and withered mycotoxin-contaminated grain kernels. Great effort has been accomplished to combat FHB in the past decades; however, solutions to prevent FHB damage are limited. The development of quantitative resistant cultivars is considered a sustainable and highly desired approach to reducing FHB damage.

This review aims to combine novel data related to the potential ability of pathogens to evolve aggressiveness, erosion of quantitative head blight resistance in wheat and barley, and applying gene pyramiding which enhances host resistance to FHB infection to achieve durable head blight resistance.

Although FHB-resistance resources have been successfully utilized by resistant parents in wheat and barley breeding programs globally, this policy does not ensure high resistance to FHB since resistance will erode due to aggressiveness shifts of the head blight population. The increasing practice of monoculture wheat and barley cultivation has perhaps raised the rate of head blight pathogen evolution and obligated the natural balance shifting in favor of the pathogen, creating more repeated and grave epidemics, even in provinces where FHB has not been earlier recorded. More aggressive FHB populations have emerged in the field and under experimental laboratory conditions. It suggests adaptation followed by a spread of some strains in their environment, including adaptation to FHB-resistant breeds and possible erosion of wheat and barely resistance. Therefore, the pyramiding of several QTLs with high impact in one cereal cultivar may extend durability.

If a pyramiding of multiple resistances improving QTL combined with selection against suspected susceptibility factors is achieved in novel cultivars, the evolution of FHB pathogens might be slowed owing to reduced exposure to the pathogen, disruptive selection on FHB populations and subsequently reduced fitness of fusarium fungi. This would stabilize the pathogen population and contribute to the durability of FHB resistance.