The Diversity of Associated Microorganisms in Different Organs and Rhizospheric Soil of Arctium lappa L.

Arctium lappa L. is widely used for medicinal purposes across China, and significant effort has been directed toward enhancing its quality. Association with microorganisms has been shown to influence both plant growth and metabolites, providing a possible avenue for its quality improvement. In this study, we investigated the microorganism compositions of the root, stem, leaf, fruit and rhizospheric soil of A. lappa through high-throughput Illumina sequencing of 16S rRNA genes and ITS regions. A total of 796,891 16S rRNA and 626,270 ITS reads were obtained from the samples. Analysis of the sequencing data revealed that bacterial and fungal communities were more diverse in the rhizospheric soil sample compared with other samples. Cyanobacteria, Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes phyla were found in all samples. Cyanobacteria was particularly enriched in the root, stem, leaf and fruit at 88.59%, 86.15%, 98.31% and 93.57%, respectively; Actinobacteria was the highest in rhizospheric soil, at 37.53%. Ascomycota was the most dominant fungal phylum, representing 69.17%, 58.18%, 87.93%, 90.18% and 80.21% in the root, stem, leaf, fruit, and rhizospheric soil, respectively. Several novel unclassifiable bacterial and fungal species were also detected. In total, we detected about 922 bacterial and 334 fungal species, which include a number of unclassifiable species. Additionally, the root, stem, leaf, fruit and rhizospheric soil of A. lappa were sources for screening new bioactive metabolites.

Xanthium italicum, Xanthium strumarium and Arctium lappa as new hosts for Diaporthe helianthi.

Sunflower (Helianthus annuus) stem canker caused by Diaporthe helianthi is one of the most important sunflower diseases in Croatia. Until recently, sunflower was the only known host for D. helianthi. In our research carried out in the area of Eastern Croatia, isolates of Diaporthe/Phomospis were collected from Xanthium italicum, X. strumarium and Arctium lappa. Using morphological, cultural and molecular ITS rDNA data, isolates from these weeds were identified as D. helianthi. The following isolates were used in the pathogenicity test: one isolate originated from sunflower (Su5/04), three from X. italicum (Xa2, Xa3 and Xa5), two from X. strumarium (Xa9 and Xa12), one from Xanthium sp. (Xa13) and one from A. lappa (Ar3). According to the results, it was determined that isolate Xa5 (originated from X. italicum) was the most pathogenic to sunflower stems. The average length of the lesion was 11.3 cm. The lowest level of pathogenicity was found in Xa9 (isolated from X. strumarium). The length of the lesion was 0.1 cm.