<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>Apple scab caused by the heterothallic ascomycetous fungus <italic>Venturia inaequalis</italic> is one of the most severe diseases in apple-growing regions worldwide. Annual sexual reproduction of the pathogen ensures the formation of populations with high variability and better adaptability to resistant cultivars. The present study aimed to assess the virulence of the <italic>V. inaequalis</italic> population in the experimental orchard where introduction, evaluation and breeding of apple cultivars are carried out, and the apple germplasm collection of Latvia is located. Fifteen differential <italic>Malus</italic> genotypes, obtained within the international Vinquest initiative, were planted in 2016 in the germplasm collection sector of the orchard in five blocks, each containing one tree of each geno-type. In 2017–2021, apple scab symptoms on the leaves were scored according to the methodology used in the Vinquest network. The disease severity increased with each vegetation season, and more genotypes were affected, reaching the maximum in 2021 and clearly indicating the infection source build-up and pathogen’s adaptation on particular genotypes due to the absence of scab control. At least four races of <italic>V. inaequalis</italic> were found to be established in Latvia, and the resistance genes <italic>Rvi1, Rvi3, Rvi4</italic>, and <italic>Rvi8</italic> have been overcome. On h(9) and h(13), the first symptoms appeared in 2021, indicating the first signs of <italic>Rvi9</italic> and <italic>Rvi13</italic> gene breakdown.</p>
</abstract>

Apple scab caused by the heterothallic ascomycetous fungus Venturia inaequalis is one of the most severe diseases in apple-growing regions worldwide. Annual sexual reproduction of the pathogen ensures the formation of populations with high variability and better adaptability to resistant cultivars. The present study aimed to assess the virulence of the V. inaequalis population in the experimental orchard where introduction, evaluation and breeding of apple cultivars are carried out, and the apple germplasm collection of Latvia is located. Fifteen differential Malus genotypes, obtained within the international Vinquest initiative, were planted in 2016 in the germplasm collection sector of the orchard in five blocks, each containing one tree of each geno-type. In 2017–2021, apple scab symptoms on the leaves were scored according to the methodology used in the Vinquest network. The disease severity increased with each vegetation season, and more genotypes were affected, reaching the maximum in 2021 and clearly indicating the infection source build-up and pathogen’s adaptation on particular genotypes due to the absence of scab control. At least four races of V. inaequalis were found to be established in Latvia, and the resistance genes Rvi1, Rvi3, Rvi4, and Rvi8 have been overcome. On h(9) and h(13), the first symptoms appeared in 2021, indicating the first signs of Rvi9 and Rvi13 gene breakdown.

Evaluation of Apple Scab and Occurrence of <italic>Venturia Inaequalis</italic> Races on Differential <italic>Malus</italic> Genotypes in Latvia

Latvia University of Life Sciences and Technologies

Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Evaluation of Apple Scab and Occurrence of  Races on Differential  Genotypes in Latvia

Apple scab caused by the heterothallic ascomycetous fungus Venturia inaequalis is one of the most severe diseases in apple-growing regions worldwide. Annual...

Evaluation of Apple Scab and Occurrence of Venturia Inaequalis Races on Differential Malus Genotypes in Latvia

Published Online: Oct 14, 2022

Page range: 488 - 494

Received: Feb 08, 2021

Accepted: Jun 27, 2022

DOI: https://doi.org/10.2478/prolas-2022-0075

Keywords
diversity, fungi, plant pathogen, resistance, virulence

© 2022 Olga Sokolova et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Evaluation of Apple Scab and Occurrence of Venturia Inaequalis Races on Differential Malus Genotypes in Latvia

Published Online: Oct 14, 2022

Page range: 488 - 494

Received: Feb 08, 2021

Accepted: Jun 27, 2022

DOI: https://doi.org/10.2478/prolas-2022-0075

Keywordsdiversity, fungi, plant pathogen, resistance, virulence

© 2022 Olga Sokolova et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
diversity, fungi, plant pathogen, resistance, virulence