First report of leaf spot caused by Nigrospora hainanensis on Oxalis corymbosa in China

Oxalis corymbosa DC. introduced into China as an ornamental plant in the mid-19th century is commonly known as an important medicinal and edible perennial herb (Zhou et al. 2021). The plant native to South America is also an invasive and widely distributed weed found in agricultural farms, gardens, and lawns, especially in sugarcane fields of Guangxi province, China. The coverage rate of O. corymbosa in sugarcane fields was normally more than 70%, sometimes up to 100%. In March of 2021, a leaf spot disease of O. corymbosa from sugarcane fields was encountered in Nanning city of Guangxi province, China. Early symptoms appeared as small yellowish round spots. The spots turned to be irregularly, usually exhibiting pale brown necrosis in the center with dark brown necrotic well-defined margins. Severely infected leaves turned to be blighted, then dead. To isolate the pathogen, diseased leave tissue fragments (4 mm × 4 mm) were soaked in 75% ethanol for 10 s followed by 2% sodium hypochlorite for 1 min, and rinsed by sterile water for three times. They were transferred to potato dextrose agar (PDA) medium cultured at 25 °C. Pure cultures were obtained by collected hypha tip from upcoming colonies. The colony features were similar to each other, floccose, white at first, becoming brown, dark brown or black on PDA after 7 days fully covered the 90 mm petri-dishes. Conidial determination were conducted on synthetic nutrient-poor agar medium (SNA) according to Wang et al. (2017). Conidia abundantly dispersed on SNA arising from conidiophores, which normally reduced to conidiogenous cells generated from hyphae. The conidiogenous cells were monoblastic, hyaline, globose or ampulliform, 6–8.5 (–12.5) × 5–7.5 (–9) μm in size (n=50). Conidia were solitary, smooth, black, sphaerical or ellipsoidal, (11–) 13–16.5 × (8–) 10–15.5 μm in size (n=100). Setae were not observed during the observation. The fungus was identified as Nigrospora sp. based on the morphology. One of the representative strains (FSC-3) was selected for genomic DNA extraction. The sequences of transcribed spacer region of rDNA (ITS), the partial translation elongation factor (TEF1), and the Beta-tubulin fragment (TUB) were respectively amplified using primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F and EF2 (Carbone & Kohn 1999, Crous et al. 2013) and Bt2a and Bt2b (Glass & Donaldson 1995), deposited in the NCBI GenBank with accession numbers of OK083685 (541 bp), OK184809 (481 bp) and OK086377 (421 bp). BLASTn analysis showed that those ITS, TEF1 and TUB gene sequences shared 99%-100% identity with the type strain (CGMCC3.18129) of Nigrospora hainanensis (GenBank accession nos. NR153480, KY019415, KY019464, respectively). In addition, a maximum likelihood analysis using concatenated gene sequences of ITS, TEF1 and TUB was performed in RAxML v.7.2.8 (Stamatakis 2006) implementing the model of GTRCAT with 1,000 bootstrap replicates. The phylogenetic results indicated that the strain FSC-3 was N. hainanensis, which also confirmed after a morphological comparison with N. hainanensis (Wang et al. 2017). Pathogenicity was tested on living Oxalis corymbosa leaves (3 plants for each test) arising from cultivated roots grown for three weeks. It was conducted by dropping 5 μL conidial suspensions (105 conidia / mL) on the living leaves (two sites per leave) incubated in separate containers at 25 °C with 90-100% relative humidity after inoculation. Controls were treated with sterile distilled water. Pale brown small spots came up after 24 h, and then extended to brown larger spots. Symptoms after inoculation were similar to field ones, while the control plants remained healthy. The pathogenicity test was repeated twice with the similar results. Re-isolation of the pathogen from the inoculated leaves was determined based on morphology and sequence analysis to fulfill Koch's postulates. Nigrospora hainanensis had been found from diseased root and leaf tissues of sugarcane in Liuzhou city, Guangxi province (Raza et al. 2019). The results indicated that O. corymbosa was another host in sugarcane fields in Guangxi, China. To our knowledge, this is the first report of Nigrospora hainanensis causing leaf spot on Oxalis corymbosa in China.

Analysis of Clinical Characteristics of 556 Spinal Tuberculosis Patients in Two Tertiary Teaching Hospitals in Guangxi Province

Spinal tuberculosis (STB), which accounts for half of musculoskeletal tuberculosis, is among the leading causes of extrapulmonary tuberculosis. Guangxi Province, located in southern China, is among the most severely affected provinces in China. In this study, we collected and analyzed data from 2 Class-A tertiary teaching hospitals in Nanning City, Guangxi Province, from 2011 to 2019, with the aim of providing reference points for the prevention, diagnosis, treatment, and prognosis analysis of STB, using the epidemiological characteristics of 556 STB cases. Our results revealed that males had a slightly higher incidence (50.17%) compared to females (49.83%), with 64.93% of cases falling between the ages of 18 and 45 years. Cases from rural communities accounted for 63.49% of the reviewed cases. The average time between onset of symptoms and hospitalization was 18.0 months (range: 1 day-220 months). The most commonly reported symptoms were lower back pain (78.60%), radicular pain (51.98%), and systemic toxemia (43.53%). Additionally, 53.98% of the reviewed cases had varying degrees of neurological impairment. The main pathological lesion locations were the lumbar spine (43.53%) and thoracic spine (32.55%). Among them, 72.66% of cases involved at least 2 vertebral segments, and 62.77% of cases presented with paravertebral abscesses. Among the cases reviewed, 90.65% underwent antituberculosis chemotherapy prior to surgery. Following treatment, the cure rate was 78.41%, while 3.78% of patients had postoperative relapse. There were cases of concomitant illnesses among the cases reviewed, 40.65% of patients also had pulmonary tuberculosis, 15.29% had hepatitis B, 13.30% had diabetes, and 7.91% had hypertension. Our results still demonstrate that spinal tuberculosis remains a serious public health problem in Guangxi Province. Thus, preventive measures should be directed towards rural residents with comorbidities such as the elderly and diabetic.

Phyllagathis chongzuoensis (Melastomataceae), a new species from Guangxi, China

Phyllagathis chongzuoensis, a new species from Guangxi Province, China, is described here. It is similar to P. erecta in having stiffly papery leaf blades with abaxially furfuraceous indumentum, similar leaf vernation, umbellate paniculate inflorescences and cup-shaped capsules, but differs in stoloniferous stem with indistinct internodes, shorter petioles, and obovate to suborbicular leaf blades with irregularly denticulate margin. Phylogenetic analyses based on nrITS and plastid genome confirmed that it is close to P. erecta.

First Report of Burkholderia cepacia Causing Finger-Tip Rot on Banana Fruit in the Guangxi Province of China

Banana (Musa acuminata) is one of the most popular and widely consumed fruit crops in the world. During late October to early November 2020, a banana finger-tip rot disease was observed in the banana (cultivar ‘Brazil’, AAA group) orchard of about 12 hectares located in Zhongcun, Zhangmu Town, Fumian District, Yulin City, Guangxi province, China. The disease incidence was about 0.5% at the surveyed field. Infected fingers and their tips were usually normal in the appearances and then turned to brown to black discoloration in the central fruit pulp adjacent to the fingertips (Fig. 1A). In severe infection, diseased fingers showed brown to black discoloration in both the central and the periphery fruit pulp, and along the longitudinal axis throughout the fruit (Fig. 1B-C). The symptomatic banana fingers were surface-disinfected with 1% sodium hypochlorite for 30 sec, 75% ethanol for 30 sec then rinsed three times with sterile distilled water. The flesh tissues were ground in a sterile mortar and soaked in 1 ml of sterile distilled water for 30 min. A 50 μl of tissue suspensions was streaked onto Luria-Bertani (LB) medium. Single colonies were picked and re-streaked onto new LB medium. The cultures were incubated at 37°C for 24 h. Two representative strains, GX and GX2, were obtained from symptomatic pulps and used in the following studies. To molecularly identify the bacterial species, we performed a polymerase chain reaction (PCR) using 16S rRNA and recA primers (Turner et al. 1999; Lee and Chan 2007) and amplified 1,442 bp and 1,019 bp sequences, respectively. The amplified sequences were deposited in GenBank under the accession numbers MZ267253 and MZ961355 for the 16S rRNA and MZ287336 and MZ983484 for the recA genes. BLASTn searches shared more than 99% similarity with the reference sequences of B. cepacia strains (MK680073.1 and KC261418.1 for 16S rRNA; AY598028.1 and KF812859.1 for recA). Phylogenetic trees were constructed using the 16 rRNA and recA sequences and showed that the representative strains, GX and GX2, strongly clustered with B. cepacia type strains (Fig. 2). To further determine the genomovars of strain GX, we used specific PCR primers to the B. cepacia epidemic strain marker (BCESM), type III secretion gene cluster (bcscV) and cable pilin subunit gene (cblA) (Lee and Chan 2007; Ansari et al. 2019). The presence of bcscV and BCESM were confirmed by PCR, while cblA was not observed in the strains GX and GX2, suggesting that the isolated strains belong to B. cepacia genomovar III and are slightly different from the Iranian and Taiwan strains of B. cepacia (Lee and Chan 2007; Ansari et al. 2019). Pathogenicity test was conducted on banana fingers (cultivar ‘Zhongjiao No.3’) at the immature and full ripe stages. A final suspensions of 106 CFU/ml, was injected into the banana fingers (100 μl per finger) through the center of the stigma (Lee and Chan 2007; Ansari et al. 2019). The fingers inoculated with sterile water were used as negative control. To maintain humidity, the treated fingertips were wrapped with Parafilm. For each treatment, ten independent replicates were conducted. At 10 days post-inoculation (dpi), the pulp of immature bananas exhibited reddish brown decaying tissue, which symptoms were similar to those observed in the field (Fig. 1D). Moreover, the pulp tissues of ripe bananas showed a dark brown discoloration in the tip at 5 dpi, whereas the controls remained symptomless (Fig. 1E). The same bacterium was re-isolated from diseased tissues and its identification confirmed by 16S rRNA, thus fulfilling the Koch’s postulates. This disease was first described in Honduras in Latin America, and then reported in Taiwan province of China, and Iran (Buddenhagen 1968; Lee et al. 2003; Ansari et al. 2019). To our knowledge, this is the first report of banana finger-tip rot caused by B. cepacia in the Guangxi province, China. It is necessary to determine the distribution of B. cepacia and to prevent its spread in Guangxi province of China.

Survey of low pathogenic avian influenza viruses in live poultry markets in Guangxi Province, Southern China, 2016–2019

Low pathogenic avian influenza viruses (LPAIVs) have been widespread in poultry and wild birds throughout the world for many decades. LPAIV infections are usually asymptomatic or cause subclinical symptoms. However, the genetic reassortment of LPAIVs may generate novel viruses with increased virulence and cross-species transmission, posing potential risks to public health. To evaluate the epidemic potential and infection landscape of LPAIVs in Guangxi Province, China, we collected and analyzed throat and cloacal swab samples from chickens, ducks and geese from the live poultry markets on a regular basis from 2016 to 2019. Among the 7,567 samples, 974 (12.87%) were LPAIVs-positive, with 890 single and 84 mixed infections. Higher yearly isolation rates were observed in 2017 and 2018. Additionally, geese had the highest isolation rate, followed by ducks and chickens. Seasonally, spring had the highest isolation rate. Subtype H3, H4, H6 and H9 viruses were detected over prolonged periods, while H1 and H11 viruses were detected transiently. The predominant subtypes in chickens, ducks and geese were H9, H3, and H6, respectively. The 84 mixed infection samples contained 22 combinations. Most mixed infections involved two subtypes, with H3 + H4 as the most common combination. Our study provides important epidemiological data regarding the isolation rates, distributions of prevalent subtypes and mixed infections of LPAIVs. These results will improve our knowledge and ability to control epidemics, guide disease management strategies and provide early awareness of newly emerged AIV reassortants with pandemic potential.

Two new species of cricket genus Anaxiphomorpha Gorochov, 1987 (Orthoptera, Trigonidiidae, Trigonidiinae) in China

Two new species, Anaxiphomorpha nonggangensissp. nov. and Anaxiphomorpha manereserratussp. nov., are reported from Guangxi Province, China. Descriptions and illustrations for the new species and a key to all known species of Anaxiphomorpha are provided.

Classification and Disintegration Characteristics of the Carboniferous Rocks in Guangxi, China

To investigate the disintegration characteristics of the carbonaceous rocks in Guangxi Province, the typical carbonaceous rocks in the section exposed by the Hechi-Baise Expressway were investigated in this study. First, based on their mineral compositions and contents, the carbonaceous rocks were divided into four types: carbonate chert, carbonaceous argillaceous limestone, carbonaceous illite clay mudstone, and carbonaceous illite clay shale. Then, through indoor wet-dry cyclic disintegration test, the disintegration characteristics of the four types of rocks were studied. The test results showed the following: (1) the disintegration residues of the carbonate chert and the carbonaceous argillaceous limestone decrease linearly as the number of wetting-drying cycles increases. (2) The disintegration index of the carbonaceous illite clay mudstone and the carbonaceous illite clay shale decreases exponentially as the number of wetting-drying cycles increases. (3) As the number of wetting-drying cycles increases, the disintegration index curves of the carbonaceous illite clay mudstone and the carbonaceous illite clay shale samples gradually become stable until the disintegration of the samples is completed. (4) The disintegration of carbonaceous rocks is mainly affected by the clay content, followed by the structural form, but it cannot be ignored.

First Report of the Root-Knot Nematode, Meloidogyne enterolobii, on Sweet potato in Guangxi Province, China

Sweet potato (Ipomoea batatas Lam.) is the seventh most widely cultivated food crop in the world and the sixth most widely cultivated food crop in China. In June 2021, sweet potato plants were found to be displaying nutrient deficiencies with red leaves in a sweet potato field in Hepu County, Beihai City, Guangxi Province (21°37′43.41"N，109°10′58.74"E). Black irregular protuberant scars on tubers and nodular galls on roots were found. Thirty-five sweet potato ‘Variety Guiziweishu No. 1’ tubers were randomly collected and 97% were infected with root-knot nematodes. Females (n = 20) had perineal patterns that were oval, with moderate to high dorsal arches, the lateral field was not obvious or absent. Morphological measurement of females (n = 20) were made from micrographs taken with a microscope (Axio Imager, Z2, ZEISS). Measurements (mean + standard error) were: body length (BL) = 932.8 ± 18.4 μm; maximum body width (BW) = 588.8 ± 22.0 μm; vulval slit length = 19.6 ± 0.6 μm; and, vulval slit to anus distance = 22.3±0.8 μm. Morphological measurements of second-stage juveniles (J2; n = 20) were: BL =512.0± 5.9 μm; BW = 17.4 ± 0.6 μm; Stylet length = 13.4 ± 0.2 μm; dorsal pharyngeal gland orifice to stylet base (DGO) =3.4 ± 0.0 μm; and, hyaline tail length = 17.6 ± 0.5 μm. These morphological characteristics fit those of the original description for Meloidogyne enterolobii (Yang and Eisenback 1983). Molecular analyses were conducted to confirm species identification. Genomic DNA was extracted from 12 single J2 (Luo et al. 2020). The rDNA-internal transcribed spacer (ITS) region was sequenced using primers V5367/26S (5′-TTGATTACGTCCCTGCCCTTT-3′/5′-TTTCACTCGCCGTTACTAAGG-3′) (Vrain et al. 1992), and the D2–D3 fragment of the 28S rRNA genes using primers D2A/D3B (5′-GTACCGTGAGGGAAAGTTG-3′/5′-TCGGAAGGAACCAGCTACTA-3′) (De Ley et al. 1999). The target gene sequences were 733 bp (GenBank accession no. MZ413814) and 733 bp (MZ411468), respectively; they were all 99-100% similar to those of M. enterolobii sequences available in the GenBank. Species identification was also confirmed using PCR to amplify rDNA-IGS2 with M. enterolobii-specific primers Me-F/Me-R (5′-AACTTTTGTGAAAGTGCCGCTG-3′/5′-TCAGTTCAGGCAGGATCAACC-3′). The electrophoresis results showed a bright band (∼200 bp) only in the lane with the M. enterolobii-specific primers, similar in size to that previously reported for M. enterolobii (Long et al. 2006). Therefore, this Meloidogyne sp. population on sweet potato was identified as M. enterolobii based on its morphological and molecular characteristics. To verify the pathogenicity of nematodes, sweet potato ‘Variety Guiziweishu No. 1’ seedlings were individually planted in 18 cm diameter, 11 cm deep plastic pots containing 1000 cm3 autoclaved sandy soil (sand/soil = 3:1). A total of 15 seedlings were inoculated with 10,000 eggs (the population was same with nematode population in soil the field) and 5 seedlings without eggs were used as a control. Plants were maintained at 25-28°C in a greenhouse. After 2 months, root of inoculated plants exhibited elongated swellings similar to symptoms observed in the field. The noninoculated plants did not have any galls or swelling. A reproduction factor (nematode final population density/initial population density) value of 18.6 was obtained. These results confirmed the nematodes’ pathogenicity. To our knowledge, this is the first report of M. enterolobii on a member of the Convolvulaceae in Guangxi Province. In 2014, the nematode on sweet potato was reported in Guangdong Province (Gao et al. 2014). Guangxi Province is the largest producer of sweet potato in south China and is the third top producing region in the whole country. Meloidogyne enterolobii is a potential risk to the production of sweet potato in this region, and control measures are needed to prevent any further spread.

Systematic Investigation of Plant-Parasitic Nematodes Associated with Main Subtropical Crops in Guangxi Province, China

Plant parasitic nematodes (PPNs) are a pathogenic group that causes momentous crop yield loss by retarding plant growth and development through plant parasitization. In this study, the distribution of PPNs based on the main crops in Guangxi Province of China was investigated. A total of 425 samples of soil or roots from sugarcane, rice, maize, and soybean were collected in 68 counties, and a total of 48 order/family/genera of PPNs were identified, of which some genera were found in more than one crop. A total of 31 order/family/genera of PPNs were found in rice, among which Hirschmanniella was the most abundant, accounting for 79.23%, followed by Tylenchorhynchus (34.43%). Forty order/family/genera were observed in maize, of which the dominant genera were Pratylenchus and Tylenchorhynchus at 45.14% and 32.64%, respectively. In addition, 30 order/family/genera of PPNs were detected from sugarcane, and the percentages of Tylenchorhynchus and Helicotylenchus were 70.42% and 39.44%, respectively. The main crop of Eastern ecological regions was rice, with a high frequency of Hirschmanniella. The greatest frequency of Pratylenchus was found in the Western eco-region, which had a large area of maize. In the Northern eco-region, rice and maize were popular, with abundant Hirschmanniella and Helicotylenchus. In the Central eco-region, Pratylenchus was detected on the main crop of sugarcane. Hirschmanniella (72.94%) was dominant in clay, and Tylenchorhynchus (54.17%) showed the highest frequency in loam. The distribution of PPNs varied with different altitudes. The diversity of this phenomenon was closely related to host plants. These results could improve understanding of the distribution of PPNs and provide important information for controlling PPNs.