Major Genes for Powdery Mildew Resistance in Research and Breeding of Barley: A Few Brief Narratives and Recommendations

TL;DR

This paper discusses strategies for breeding barley resistant to powdery mildew, emphasizing the use of durable resistance genes like Mlo.

Contribution

The paper recommends the adoption of the durable Mlo resistance gene in barley breeding programs.

Findings

Major genes for powdery mildew resistance in barley conform to a gene-for-gene system with a highly adaptable pathogen.

The Mlo gene provides non-specific, durable resistance and is prevalent in Central and Western European spring barley varieties.

Breeding programs should prioritize durable resistance genes over hypersensitive resistance genes for long-term effectiveness.

Abstract

Genetic resistance is a sustainable way to protect crops from diseases, and breeding resistant varieties is a key objective. However, diseases are caused by pathogens with different life cycles, and the importance of individual evolutionary forces plays a key role in the adaptation of their populations. Therefore, strategies for the use of genetic resistance resources can vary depending on the plant pathosystem. Numerous major genes confer hypersensitive resistance to powdery mildew—one of the most common diseases in barley—but these genes conform to the gene-for-gene system of an extremely diverse and adaptable pathogen. When such resistance genes are transferred into commercial varieties, their efficiency in the field is soon overcome and replacement with newly developed resistant varieties can be slow. Hence, specific resistance genes should not be used in barley breeding programs. Only one monogenic, non-hypersensitive, non-specific and durable major resistance Mlo is known. This predominates in Central and Western European spring varieties and should be widely adopted by barley breeders elsewhere and in other crops where such type of resistance is found. In this paper, the relevant aspects involved in breeding barley resistant to powdery mildew are discussed, with conclusions supported by practical examples. Additionally, future directions for barley improvement are proposed.

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