The microbial communities in rhizosphere soil play important roles in plant health and crop productivity. However, the microbial community structure of rhizosphere soil still remains unclear. In this study, the composition, diversity and function of the microbial communities in the rhizosphere soil of healthy and diseased plants were compared using Illumina MiSeq high-throughput sequencing. The Sobs (richness) and Shannon (diversity) indices of the soil microbial communities were higher in the rhizospheres of 2- and 3-year-old susceptible plants than in those of the healthy plants. With the increase in planting time, the numbers of fungi tended to decrease, while those of the bacteria tended to increase. Fungal diversity could be used as a biological indicator to measure the health of Knoxia roxburghii. The microbial composition and differential analyses revealed that the rhizosphere soil infested with fungi had a higher relative abundance at the phylum level in Ascomycota and Basidiomycota, while the bacteria had a higher relative abundance of Chloroflexi and a lower relative abundance of Actinobacteriota. At the genus level, the rhizosphere soil infested with fungi had relatively more abundant unclassified_f__Didymellaceae and Solicoccozyma and relatively less abundant Saitozyma and Penicillium. The bacterial genus norank_f__Gemmatimonadaceae was the most abundant, while Arthrobacter was less abundant. In addition, the abundance of Fusarium in the fungal community varied (p = 0.001). It tended to increase in parallel with the planting years. Therefore, it was hypothesized that the change in the community composition of Fusarium may be the primary reason for the occurrence of root rot in K. roxburghii, and the change in the abundance of Fusarium OTU1450 may be an indication of the occurrence of root rot in this species. The community function and prediction analyses showed that the pathogenic fungi increased with the increase in planting years. In general, soil fungi can be roughly divided into three types, including pathotrophs, symbiotrophs, and saprotrophs. An analysis of the differences in the prediction of different rhizosphere functions showed that D and L were significantly different in the COG enrichment pathway of the K. roxburghii rhizosphere bacteria (p < 0.05). The soil physical and chemical properties, including the pH, AK, total potassium (TK), and catalase (S_CAT), had the most significant effect on the soil fungal community, and most of the soil physical and chemical properties significantly correlated with the bacterial community. This study demonstrated that the occurrence of root rot had an important effect on the diversity, structure and composition of microbial communities. In addition, the results will provide a theoretical basis to prevent and control root rot in K. roxburghii.

Knoxia roxburghii (syn. Knoxia valerianoides), locally known as ‘Zi Daji’, is a perennial herb that belongs to the Rubiaceae family, cultivated in different areas of China and recognized for its me...

Rhizome rot is a destructive soil-borne disease of Polygonatum kingianum and adversely affects the yield and sustenance of the plant. Understanding how the causal fungus Fusarium oxysporum infects P. kingianum may suggest effective control measures against rhizome rot. In germinating conidia of infectious F. oxysporum, expression of the zinc finger transcription factor gene Zfp1, consisting of two C₂H₂ motifs, was up-regulated. To characterize the critical role of ZFP1, we generated independent deletion mutants (zfp1) and complemented one mutant with a transgenic copy of ZFP1 (zfp1 tZFP1). Mycelial growth and conidial production of zfp1 were slower than those of wild type (ZFP1) and zfp1 tZFP1. Additionally, a reduced inhibition of growth suggested zfp1 was less sensitive to conditions promoting cell wall and osmotic stresses than ZFP1 and zfp1 tZFP1. Furthermore pathogenicity tests suggested a critical role for growth of zfp1 in infected leaves and rhizomes of P. kingianum. Thus ZFP1 is important for mycelial growth, conidiation, osmoregulation, and pathogenicity in P. kingianum.

Angelica sinensis (Oliv.) Diels, is a perennial herbaceous plant of the Umbelliferae family. It has a long history of cultivation and is highly valued as a traditional Chinese medicine in China (Zhang et al. 2012). In September 2023, leaf blight on A. sinensis with an average disease incidence of 56% was recorded in an approximately 6.7-ha production field in Lijiang, Yunnan province, China (26.8215°N, 100.2369°E). At first, small, chlorotic lesions appeared on the leaves. They subsequently increased in density and gradually merged, causing leaves to yellow and wither. Ultimately the blight casused death of the entire foliage. In order to identify the causal agent, cross-sectional segments (5×5 mm2) were cut from the edge of leaf lesions, surface disinfected with a 1% sodium hypochlorite solution for 3 min and rinsed three times with sterile distilled water. They were subsequently placed on potato dextrose agar (PDA) plates and incubated for 3 days under a 12-h photoperiod at 28℃. A total of ten isolates with similar morphological characteristics were obtained by single spore isolation. After 10 days of incubation on PDA, the colony morphology of these isolates was characterized by a brownish central area with a white edge. Aged colonies became wrinkled in the center of the colony. Conidia (n = 30) were elliptical and brown, with a size range of 4.11 to 6.55 μm (average 5.37±0.74 μm) × 3.17 to 4.62 μm (average 3.92±0.43 μm). Chlamydospores (n = 30) formed chains in series, spherical or elliptical in shape, ranging from yellow-brown to dark brown, with a size range of 12.30 to 13.70 μm (average 12.98±0.46 μm) × 4.20 to 5.30 μm (average 4.63±0.26 μm). The nuclear ribosomal internal transcribed spacer region (ITS), the second largest subunit of RNA polymerase II (RPB2), and the 28S nuclear ribosomal large subunit rRNA (LSU) region of two isolates were amplified with the primer pairs ITS1/ITS4 (White et al. 1990), fRPB2-5F/fRPB2-7cR (Liu et al. 1999), and LR0R/LR5 (Schoch et al. 2012), respectively. These amplicons were sequenced bidirectionally and assembled. The two isolates produced the same nucleotide sequences, and the sequences of a representative isolate (AsDp1) were deposited in GenBank. BLASTn analyses showed that the ITS (PP510616), RPB2 (PP526010), and LSU (PP550143) sequences of isolate AsDp1 were 100%, 99.66%, and 100% identical with those of Didymella pomorum ex-type isolate CBS 354.52 (MH857081, KT389616, and MH868616), respectively. A phylogenetic tree was constructed based on the ITS, RPB2, and LSU concatenated nucleotide sequences using the maximum likelihood method in MEGAX. Isolate AsDp1 was clustered with four D. pomorum isolates. According to the morphological and nucleotide sequences analyses, isolate AsDp1 was identified as D. pomorum (Chen et al. 2015). To determine pathogenicity, 1-year-old A. sinensis plants (approximately 20 cm tall) grown in 7-liter pots filled with sterilized field soil were sprayed until runoff with a 1×106 conidia/ml suspension of isolate AsDp1 onto the foliage, while control plants were sprayed with sterile water. All plants were cultivated under a 12-h photoperiod at 25℃. The pathogenicity tests were performed in triplicate with ten plants in each treatment. After fifteen days, numerous chlorotic lesions appeared on the leaves of all inoculated plants. The symptoms were similar to those found on naturally infected plants in the field, while the control plants remained asymptomatic. Subsequently, D. pomorum was reisolated from the diseased leaves, and the identity was confirmed based on its ITS sequence and morphological characteristics. D. pomorum causing stem canker on Rosa spp. was reported in Canada (Ilyukhin 2022). To our knowledge, this is the first report of D. pomorum causing leaf blight on A. sinensis in China. This etiological finding will potentially pave the way for the development of control strategies of this disease.

Fusarium oxysporum strain PkF01 is the causal agent of Polygonatum kingianum rhizome rot. Here, we report, for the first time, the genome assemblies of the F. oxysporum strain PkF01 using the PacBi...