Pathogenic fungi influencing safety of raw material of oregano (Origanum vulgare L.) in Latvia

Many fungal species infect oregano (Origanum vulgare L.) during cultivation, some of them produce substances of toxic character – mycotoxins, secondary metabolites [1]. In 2020, the research on diversity of fungi colonizing and damaging leaves of oregano was carried out. The samples of plant material were selected from an ex situ collection of aromatic and medicinal plantsʼ genetic resources. Fungi, potential causing agents, were isolated from tissue of diseased leaves and were identified by sequencing nuclear ITS-rDNA region.

Quantitatively the most extensive group were represented by Alternaria sp. (36%), Epicoccum sp. (25%) and Phoma sp. (11%). Single isolates of Ascomycota sp., Mucor sp., Botrytis sp., Stemphylium sp. and Chaetosphaeronema sp. were also obtained from the leaves of oregano.

In scientific literature it is described Alternaria species produces more than 70 phytotoxins, they are accumulated in plant tissues [2], [3]. Also is the genus Phoma are producer of mycotoxins [4]. Boeremia exigua var. exigua (syn. Phoma exigua var. exigua) we were observed in our study on oregano leaves.

The negative aspect of the occurrence of Alternaria and Boeremia exigua var. exigua) on oregano leaves, in addition to reducing the amount of ‘Herba Origani’ yield, is the ability to accumulate toxic substances, produced by the pathogens in the tissues. These species should be considered as particularly dangerous for oregano in Latvia.

• References

• 1 Zimowska B. Fungi threatening the cultivation of oregano (Origanum vulgare L.) in south-eastern Poland. Acta Sci Pol Hort Cult 2015; 14: 65-78
• 2 Kalra A, Singh HB, Pandey R. et al. Diseases in mint: causal organisms, distribution and control measures. J Herbs Spices Med Plants 2004; 11: 71-91
• 3 Tylkowska K, Grabarkiewicz-Szczęsna J, Iwanowska H. Production of toxins by Alternaria alternata and A. radicina and their effects on germination of carrot seeds. Seed Sci Tech 2003; 31: 309-316
• 4 Grinbergs D, France A, Varrelmann M. First report of Boeremia exigua var. exigua (syn. Phoma exigua var. exigua) causing black root rot on industrial chicory (Cichorium intybus var. sativum) in Chile. Plant Dis 2016; 11

Publication History

Article published online:
12 December 2022