SUSCEPTIBILITY OF LEMON BALM (Melissa officinalis L.) VARIETIES TO SEPTORIA LEAF SPOT (Septoria melissae Desm.) IN HUNGARY

Abstract

Lemon balm (Melissa officinalis L.) is a widely cultivated plant in Europe. Septoria melissae Desm. is the most important pathogen of lemon balm crops, which may cause serious yield loss by the severe leaf fall. As chemical control of the pathogen is restricted, alternative plant protection methods, like the use of tolerant varieties, should be taken under consideration. The goal of our work was to evaluate the susceptibility of three lemon balm varieties to Septoria leaf spot in field. The trials were carried out in 2016 and 2017 in Budapest-Soroksár, Hungary. Dynamics of infection showed characteristic sharp increase from the beginning of August in both years. The lowest infection levels were observed in cultivar ‘Lemona’. The disease incidence in the middle of August was 19% in the first year and 59% in the second year, while these values were over 40% and 70% in the other cultivars ‘Soroksári’ and ‘Quedlinburger Niederliegende’, respectively. The manifestation of symptomps was also significantly lighter on the ‘Lemona’ plants and they had the highest ratio of healthy leaves (81%) compared to the other cultivars. According to the data, weather conditions might modify the range of the differences among the cultivars. It was concluded that appropriate selection of varieties could be an effective and enviromental friendly plant protection method in the practice of lemon balm cultivation.

Journal of Plant Protection Research

“…The presence of the fallen infected leaves may have served as an inoculum source and thus contributed to a higher infection level on the plantations. In accordance with our previous studies (Kovács et al 2019), the breeding of disease tolerant M. officinalis varieties would be an effective tool in the plant protection of lemon balm. In order to develop the sustainable cultivation practice of this herb, further studies, including other varieties and cultivated forms of lemon balm, are needed.…”

“…Evaluation was carried out by the method described in our previous study (Kovács et al 2019). Assessments of disease level were carried out weekly from the beginning of June to the end of August in 2017 and from the end of April to the end of August in 2018.…”

“…Meyers (2007) reports a moderate resistance of the cultivar 'Citronella' against powdery mildew disease. The cultivar 'Lemona' proved to be the least susceptible to the disease development and severity of the pathogen S. melissae (Kovács et al 2019).…”

Occurrence of pathogenic fungi on commercially available medicinal plants and packaged seeds

“…officinalis was the most infected species (tab.1). In addition to the species listed above, single isolates of S. melissae and U. atrum were obtained in this study, while in field crops S. melissae is often the dominant species [13].…”