Tea gray blight disease and its existing control measures have had a negative impact on the sustainable development of tea gardens. However, our knowledge of safe and effective biological control measures is limited. It is critical to explore beneficial microbial communities in the tea rhizosphere for the control of tea gray blight. In this study, we prepared conditioned soil by inoculating Pseudopestalotiopsis camelliae-sinensis on tea seedling leaves. Thereafter, we examined the growth performance and disease resistance of fresh tea seedlings grown in conditioned and control soils. Next, the rhizosphere microbial community and root exudates of tea seedlings infected by the pathogen were analyzed. In addition, we also evaluated the effects of the rhizosphere microbial community and root exudates induced by pathogens on the performance of tea seedlings. The results showed that tea seedlings grown in conditioned soil had lower disease index values and higher growth vigor. Soil microbiome analysis revealed that the fungal and bacterial communities of the rhizosphere were altered upon infection with Ps. camelliae-sinensis. Genus-level analysis showed that the abundance of the fungi Trichoderma, Penicillium, and Gliocladiopsis and the bacteria Pseudomonas, Streptomyces, Bacillus, and Burkholderia were significantly (p < 0.05) increased in the conditioned soil. Through isolation, culture, and inoculation tests, we found that most isolates from the induced microbial genera could inhibit the infection of tea gray blight pathogen and promote tea seedling growth. The results of root exudate analysis showed that infected tea seedlings exhibited significantly higher exudate levels of phenolic acids and flavonoids and lower exudate levels of amino acids and organic acids. Exogenously applied phenolic acids and flavonoids suppressed gray blight disease by regulating the rhizosphere microbial community. In summary, our findings suggest that tea plants with gray blight can recruit beneficial rhizosphere microorganisms by altering their root exudates, thereby improving the disease resistance of tea plants growing in the same soil.

An unknown root-knot nematode was found at high density on grape roots collected from Yunnan Province. Morphometric traits and measurements, isozyme phenotypes, and molecular analysis clearly differentiated this nematode from previously described root-knot nematodes. This new species is described, illustrated and namedMeloidogyne vitissp. nov. The new species can be distinguished from otherMeloidogynespp. by a unique combination of characters. Females display a prominent neck, an excretory pore is located on the ventral region between 23rd and 25th annule behind lips, an EP/ST ratio of approximately 2.5 (1.98–2.96), a perineal pattern with two large and prominent phasmids, and a labial disc fused with the medial lips to form a dumbbell-shaped structure. Males display an obvious head region, a labial disc fused with the medial lips to form a dumbbell-shaped structure, no lateral lips, a prominent slit-like opening between the labial disc and medial lips, a distinct sunken appearance of the middle of the medial lips, and four incisures in the lateral field. Second-stage juveniles are characterized by a head region with slightly wrinkled mark, a labial disc fused with the medial lips to form a dumbbell-shaped structure, a slightly sunken appearance of the middle of the medial lips, a slit-like amphidial openings between the labial disc and lateral lips, and four incisures in the lateral field. The new species has rare Mdh (N3d) and Est phenotypes (VF1). Phylogenetic analysis based on ITS1-5.8S-ITS2, D2D3 fragments of rDNA, and coxI and coxII fragments of mtDNA sequences clearly separated the new species from other root-knot nematodes, and the closest relative wasMeloidogyne mali.Meloidogyne maliwas collected for amplifying these sequences as mentioned above, which were compared with the corresponding sequences of new species, the result showed that all of these sequences with highly base divergence (48–210 base divergence). Moreover, sequence characterized amplified region (SCAR) primers for rapid identification of this new species were designed.

To identify the root-knot nematodes (RKNs) infecting onions in Yuanmou County, Yunnan Province, morphological and molecular biological techniques were used. Observation of their life cycle and pathogenicity was conducted through artificial inoculation experiments in a greenhouse. The results show that the morphological characteristics and measurement data of the second-stage juveniles (J2s) and females of RKNs infecting onion roots are highly consistent with those of Meloidogyne graminicola (M. graminicola). Sequence alignment of the mitochondrial DNA (mtDNA) COXI region and 28S rDNA D2-D3 region revealed sequence similarities of 99.51–100.00% and 99.48–99.61%, respectively, compared with M. graminicola sequences from GenBank. The specific primers Mg-F3/Mg-R2 reliably amplified a characteristic 369 bp band. Inoculation experiments confirmed that the pathogen can complete its entire life cycle (approximately 26 days (ds)) on the roots of healthy onion seedlings, inducing typical root-knot symptoms and females. In conclusion, the pathogen was identified as M. graminicola, which is the first report of M. graminicola infecting onions in China. This study provides important theoretical support for the molecular diagnosis of onion root-knot nematode disease and the green control of Allium L. vegetables in China.

Bletilla striata (Thunb. ex Murray) Rchb. F. (Orchidaceae) is an endangered traditional Chinese medicinal plant and has been traditionally used for hemostasis and detumescence in China (Wang et al. 2022). In March of 2021, during a field survey in Xuanwei city, Yunnan province, China, some B. striata plants with symptoms of plant dwarfing and leaf yellowing were observed. Roots of diseased plants presented numerous galls, typical symptoms of root-knot nematodes (RKNs) infection. The diseased area was approximately 66667 m2, showing a patchy disease distribution pattern. To identify the species of RKNs, females and eggs were isolated from galled tissue, and second-stage juveniles (J2s) were collected from eggs hatched. Nematodes were identified through comprehensive morphological and molecular methods. The perineal pattern of females is round to ovoid with a flat or moderately high dorsal arch and has two conspicuous lateral line striae. Morphological measurements of females (n=20) included body length (L) = 702.9 ± 70.8 (556.2-780.2) μm, body width (BW) = 404.1 ± 48.5 (327.5-470.1) μm, stylet length = 15.5 ± 2.2 (12.3-18.6) μm, distance from base of stylet to dorsal esophageal gland opening (DGO) = 3.7 ± 0.8 (2.1-4.9) μm. The morphometrics of J2s (n=20), L = 438.4 ± 22.6 (354.1-464.8) μm, BW = 17.4 ± 2.0 (12.9-20.8) μm, stylet length = 13.5 ± 0.4 (13.0-14.2) μm, DGO = 3.2 ± 0.6 (2.6-4.7) μm, and hyaline tail terminus = 12.3 ± 1.9 (9.6-15.7) μm. These morphological characteristics were similar to the original descriptions of Meloidogyne javanica (Rammah and Hirschmann 1990). DNA extraction was done 60 times, each from a different single females following the method of Yang et al. (2020). Amplification of ITS1-5.8S-ITS2 region of rDNA and the coxI region of mtDNA was done by using primers 18S/26S (5′-TTGATTACGTCCCTGCCCTTT-3′/5′-TTTCACTCGCCGTTACTAAGG-3′) (Vrain et al. 1992) and cox1F/cox1R (5′-TGGTCATCCTGAAGTTTATG-3′/5′-CTACAACATAATAAGTATCATG-3′) (Trinh et al. 2019) respectively. The PCR amplification program followed the method described by Yang et al. (2021). The ITS1-5.8S-ITS2 gene sequence (768 bp, GenBank Accession No. OQ091922) showed 99.35-100% identical to the known sequences of M. javanica (GenBank Accession Nos. KX646187, MW672262, KJ739710, KP901063, MK390613). The coxI gene sequence (410 bp, OQ080070) showed 99.75%-100% identical to the known sequences of M. javanica (OP646645, MZ542457, KP202352, KU372169, KU372170). Furthermore, M. javanica species-specific primers Fjav/Rjav (5′-GGTGCGCGATTGAACTGAGC-3′/5′-CAGGCCCTTCAGTGGAACTATAC-3′) were used for PCR amplification. An expected fragment of approximately 670 bp was obtained, which was identical to that previously reported for M. javanica (Zijlstra et al. 2000). To verify pathogenicity of this nematode on B. striata, six 1.6-year-old tissue culture seedings of B. striata were maintained in 10-cm-diameter × 9-cm-high plastic pots containing a sterilized mixed soil (humus soil: laterite soil: perlite=3:1:1), and each plant was inoculated with 1000 J2s hatched from eggs of M. javanica. Three non-inoculated B. striata were used as the negative controls. All plants were placed in a greenhouse at approximately 14～26 ℃. After 90 days, the inoculated plants presented symptoms of leaf yellowing, and the roots with root knots identical to those observed in the fields. The root gall rating was 2 according to the 0-5 RKNs rating scale (Anwar and McKenry, 2002) and the reproductive factor (RF= final population/initial population) was 1.6. No symptoms or nematodes were observed on control plants. The nematode was reisolated and identified as M. javanica by morphological and molecular methods as above. To our knowledge, this is the first report of infection of M. javanica on B. striata. The infection of this economically important medicinal plant with M. javanica could pose a great threat to B. striata production in China, and further research will be necessary to develop control strategies.