Status, gaps and perspectives of powdery mildew resistance research and breeding in cucurbits

Authors: LEBEDA, ALES - Palacky University; KRISTKOVA, EVA - Palacky University; MIESLEROVA, BARBORA - Palacky University; DHILLON, NARINDER - Kasetsart University; McCreight, James - Jim

Submitted to: Critical Reviews in Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2024
Publication Date: 3/6/2024
Citation: Lebeda, A., Kristkova, E., Mieslerova, B., Dhillon, N.P.S., McCreight, J.D. 2024. Status, gaps and perspectives of powdery mildew resistance research and breeding in cucurbits. Critical Reviews in Plant Sciences. 43(4):211-290. https://doi.org/10.1080/07352689.2024.2315710.
DOI: https://doi.org/10.1080/07352689.2024.2315710

Interpretive Summary: Cucurbits are a large family of flowering plants, containing 95 genera and 950–980 species of food and ornamental plants, and wild and weedy species. This review is focused on the most important cucurbit crops melon, cucumber, squashes, and gourds, and some their wild relatives as hosts of powdery mildews. Powdery mildews are one of the most frequently encountered and easily visible group of plant pathogenic fungi. They infect above ground plant tissues, mostly leaves, though they may also colonize stems, petioles, flowers and fruits, and they are usually debilitators, not killers. These parasitic fungi have been problematic on cucurbits for a long time world-wide, causing serious economic losses in yield and quality. All economically important cucurbit crops host powdery mildew. Seven powdery mildew species with different taxonomic positions, host ranges, geographic distributions and ecological requirements are known on cucurbits. Powdery mildew taxonomy and denomination rapidly changed during last few decades through detailed analyses and clarifications. At least three powdery mildew species frequently parasitize cucurbits: the endoparasite Leveillula taurica (Lt) with marginal economic importance; and two ectoparasitic species, Golovinomyces orontii (Go), and Podosphaera xanthii (Px), which are economically important world-wide. The two major pathogens differ in ecological requirements and distribution, though they may occur together in mixed infections. They are highly variable at the population level for virulence, race identities, and fast adaptation of pathogens. Cucurbit-powdery mildew interactions are diverse and complicated, and differ between hosts and their respective pathogen genera and species. Here we present a critical overview of obstacles, gaps and recent progress in these matters for seven cucurbit genera with respect to resistance resources, genetics of resistance, genetic mapping and development of molecular markers, physiology and mechanisms of resistance, patents, and CPM resistance breeding.

Technical Abstract: Cucurbitaceae, the gourd family of flowering plants, is a very large and diverse family, the order Cucurbitales, contains 95 genera and 950–980 species of food and ornamental plants, and wild and weedy species mostly with high genetic diversity. This review is focused on the most important cucurbit crops (Cucumis sativus, Cucumis melo, Cucurbita spp., Citrullus lanatus, Momordica charantia, Lagenaria siceraria, and Luffa acutangula) and some their wild relatives as a hosts of cucurbit powdery mildews (CPM). Powdery mildews (PM) (Ascomycota, Erysiphales) are one of the most frequently encountered and easily visible group of plant pathogenic fungi with > 900 species. They are obligate biotrophs, they colonize above ground plant tissues, mostly leaves, though they may also colonize stems, petioles, flowers and fruits, and they are usually debilitators, not killers. These parasitic fungi have been problematic on cucurbits for a long time world-wide, causing serious economic losses in yield and quality. All economically important cucurbit crops host CPM. Seven PM species with different taxonomic positions, host ranges, geographic distributions and ecological requirements are known on cucurbits. CPM species taxonomy and denomination rapidly changed during last few decades through detailed analyses and clarifications. At least three PM species frequently parasitize cucurbits: the endoparasite Leveillula taurica (Lt) with marginal economic importance; and two ectoparasitic species, Golovinomyces orontii (Go), and Podosphaera xanthii (Px), which are economically important world-wide. The two pathogens differ in ecological requirements and distribution, though they may occur together in mixed infections. They are highly variable at the population level for virulence, race identities, and fast adaptation of pathogens. Cucurbit-CPM species interactions are diverse and complicated, and differ between hosts and their respective pathogen genera and species. Here we present a critical overview of obstacles, gaps and recent progress in these matters for seven cucurbit genera with respect to resistance resources, genetics of resistance, genetic mapping and development of molecular markers, physiology and mechanisms of resistance, developments in mlo-mediated resistance, patents, and CPM resistance breeding.