Resistance that stacks up: engineering rust and mildew disease control in the cereal crops wheat and barley

Abstract

SummaryStaying ahead of the arms race against rust and mildew diseases in cereal crops is essential to maintain and preserve food security. The methodological challenges associated with conventional resistance breeding are major bottlenecks for deploying resistance (R) genes in high‐yielding crop varieties. Advancements in our knowledge of plant genomes, structural mechanisms, innovations in bioinformatics, and improved plant transformation techniques have alleviated this bottleneck by permitting rapid gene isolation, functional studies, directed engineering of synthetic resistance and precise genome manipulation in elite crop cultivars. Most cloned cereal R genes encode canonical immune receptors which, on their own, are prone to being overcome through selection for resistance‐evading pathogenic strains. However, the increasingly large repertoire of cloned R genes permits multi‐gene stacking that, in principle, should provide longer‐lasting resistance. This review discusses how these genomics‐enabled developments are leading to new breeding and biotechnological opportunities to achieve durable rust and powdery mildew control in cereals.

Sources of Resistance to Powdery Mildew in Wild Barley (Hordeum vulgare subsp. spontaneum) Collected in Jordan, Lebanon, and Libya

“…In addition, modern molecular methods have to be used for the further characterization of resistance genes identified to be efficiently used in barley breeding [3,86,[92][93][94].…”

“…It is used for feed, malt, and food. Recently, the use of barley as a food has become more and more popular due to its health properties [1][2][3][4][5].…”

“…spontaneum) (Hvs). Wild barley differs from cultivated barley in several traits, including a brittle rachis, and it is considered a progenitor of cultivated barley [3,6]. Hvs occurs in Southwest Asia and, most probably due to human activities, populations of Hvs are present in Morocco, Ethiopia, and Tibet [1,2].…”

A diverse panel of 755 bread wheat accessions harbors untapped genetic diversity in landraces and reveals novel genetic regions conferring powdery mildew resistance

“…Due to this constant arms race and the low efficacy of the currently cloned Pm genes (Dracatos et al 2023), the identification of new resistance genes is needed for wheat breeding programs. More than 7,000 distinct NLR-encoding genes are estimated to be present in the wheat gene pool (Walkowiak et al 2020).…”

“…However, race-specific resistance can be rapidly overcome by pathogens by evolving AVRs to evade recognition (McDonald and Linde 2002; Mundt 2014; Brown 2015). Due to this constant arms race and the low efficacy of the currently cloned Pm genes (Dracatos et al 2023), the identification of new resistance genes is needed for wheat breeding programs. More than 7,000 distinct NLR-encoding genes are estimated to be present in the wheat gene pool (Walkowiak et al 2020).…”