Cultural and morphological features of Diaporthe spp. in phytosanitary diagnostics of Vaccinium plants

Most Diaporthe spp. belong to phytopathogenic fungi affecting a wide range of host plants, including the genus Vaccinium. These fungi often cause apical necrosis of stems, leading to plant drying out and death, and also significantly affecting the shelf life and presentation of berries. The pathogens have similar symptoms of disease manifestation on plants, and when isolated into a pure culture, they have similar cultural and morphological features, which makes it difficult to carry out reliable phytosanitary diagnostics. It should be noted that one of the species of the genus Diaporthe vaccinii Shear has a quarantine status for the Russian Federation. In this work, we conducted a study of species of the genus Diaporthe such as Diaporthe eres Nitschke, Diaporthe rudis Nitschke and Diaporthe bohemiae Guarnaccia, Eichmeier & Crous, obtained during the examination of the northern highbush blueberry plantings (V. corymbosum L.) from Kaliningrad Oblast, and the quarantine species D. vaccinii, isolated during phytosanitary examination of large cranberry planting material (V. macrocarpon L.) of imported origin (Belarus). D. bohemiae was first detected in Russia in samples of highbush blueberry from Kaliningrad Oblast. As a result of the research, a method was obtained that accelerates the formation and development of pycnidia and pycnospores, presented in the form of 2 spore types: alpha (α) and beta (β) conidia, tested species of the genus Diaporthe. By cultivating isolates on 2% malt agar with additional illumination with an erythema lamp for 7 days, diagnostically significant morphological structures of D. vaccinii were obtained. The method is applicable in laboratory research of regulated material of plants of the genus Vaccinium for the detection and identification of the causative agent of viscid rot of blueberries D. vaccinii. During the work, cultural and morphological features were described and comparative characteristics of the studied species D. vaccinii, D. eres, D. rudis and D. bohemiae were given.

1. Ali S. et al. Diaporthe eres causes stem cankers and death of young apple rootstocks in Canada // Canadian Journal of Plant Pathology. 2020. Vol. 42 (2). P. 218–227.

2. Dharmaraj K. et al. New real-time PCR assay for detecting the blueberry and cranberry twig blight pathogen //Journal of Phytopathology. 2022. Vol. 170 (10). P. 683–692.

3. EFSA PLH Panel (EFSA Panel on Plant Health). Scientific Opinion on the pest categorisation of Diaporthe vaccinii Shear // EFSA Journal. 2014. Vol. 12(7). P. 3774.

4. Farr D.F, Castlebury L.A, Pardo-Schultheiss R.A. Phomopsis amygdali causes peach shoot blight of cultivated peach trees in the southeastern United States // Mycologia. 1999. Vol. 91. P.1008–1015.

5. Farr D.F., Castlebury L.A, Rossman A.Y. Morphological and molecular characterization of Phomopsis vaccinii and additional isolates of Phomopsis from blueberry and cranberry in the eastern United States // Mycologia. 2002a. Vol. 94. P.494–504.

6. Farr D.F., Castlebury L.A., Rossman A.Y., Putnam M.L. A new species of Phomopsis causing twig dieback of Vaccinium vitis-idaea (lingonberry) // Mycol Res. 2002b. Vol. 106. P.745–752.

7. Gonzalez-Dominguez E., Caffi T., Paolini A., Mugnai L., Latinović N., Latinović J., Languasco L. and Rossi V. Development and Validation of a Mechanistic Model That Predicts Infection by Diaporthe ampelina, the Causal Agent of Phomopsis Cane and Leaf Spot of Grapevines // Front. Plant Sci. 2022. Vol. 13. P.872333.

8. Hilario S., Amaral I. A., Gonçalves F. M. M., Lopes A., Santos & Artur Alves L. Diaporthe species associated with twig blight and dieback of Vaccinium corymbosum in Portugal, with description of four new species // Mycologia. 2020. Vol.112(2). P. 293–308.

9. Lombard L. et. al. Diaporthe species associated with Vaccinium, with specific reference to Europe // Phytopathol. Mediterr. 2014. Vol. 53 (2). P. 287–299.

10. Palmateer A.J., McLean K.S., Morgan-Jones G. Concerning Phomopsis gossypii, the causal organism of boll rot of cotton //Mycotaxon. 2003. Vol. 87. P. 157–172.

11. Schilder A.M.C, Erincik O., Castlebury L., Rossman A., Ellis M.A. Characterization of Phomopsis spp. infecting grapevines in the Great Lakes Region of North America // Plant Dis. 2005. Vol. 89. P.755–762.

12. Udayanga D., Liu X., Crous P.W. et al. A multi-locus phylogenetic evaluation of Diaporthe (Phomopsis)//Fungal Diversity. 2012. Vol. 56. P. 157–171.

13. Udayanga D., Castlebury L.A., Rossman A.Y., Hyde K. D. Species limits in Diaporthe: Molecular re-assessment of D. citri, D. cytosporella, D. foeniculina and D. rudis // Persoonia – Molecular Phylogeny and Evolution of Fungi. 2014. Vol. 32. P. 83–101.

14. Udayanga D., Castlebury L.A., Rossman A.Y. et al. Insights into the genus Diaporthe: phylogenetic species delimitation in the D. eres species complex // Fungal Diversity. 2014. Vol. 67. P. 203–229.

15. Vilka L., Volkova J. Morphological Diversity of Phomopsis vaccinii Isolates from Cranberry (Vaccinium macrocarpon Ait.) in Latvia // Proc.Latv.Univ.Agr. 2015. Vol. 33. P. 8–18.

16. CABI Compendium. Diaporthe eres. (apple leaf, branch and fruit fungus). [Электронный ресурс]. URL: https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.18731 (Accessed: 08.12.2019).

17. EPPO Global Database. Diaporthe vaccinii. Distribution. [Электронный ресурс]. URL: https://gd.eppo.int/taxon/DIAPVA/distribution (Accessed: 11.09.2023).