Search

Orthorhombic olivine-structured LiTmRO4 (R = Si, Ge) ceramics were synthesized using a solid-state reaction. Promising microwave dielectric properties of εr = 8.18, τf = 13.7 ppm/°C and a high-quality factor (Q × f) of 24,274 GHz for LiTmSiO4 were obtained at 1130 °C, and εr = 8.67, τf = − 24.4 ppm/°C and Q × f = 19,231 GHz for LiTmGeO4 were achieved at 1090 °C. According to the bond valence results, Tm3+ and Ge4+ presented a compressed state, but Li+ exhibited a strong rattling state in LiTmGeO4, which led to a higher εr than εtheo. The integrated effect of the rattling cations (Li+ and Si4+) and a compressed cation (Tm3+) in LiTmSiO4 resulted in a smaller positive deviation ∆εr. The larger packing fraction of LiTmSiO4 contributed to a higher Q × f than that of LiTmGeO4. The R–O bond in both ceramics played a leading role in influencing Q × f according to the Phillips–Van Vechten–Levine chemical bond theory. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the status of weed Solanum nigrum L. as a transitional host for Meloidogyne enterolobii and its effect on the population base of the nematodes in the next season. The nematode species infecting S. nigrum L. in a fallow field was identified by morphological identification and molecular diagnosis, and parasitic characteristics of the nematodes in S. nigrum L., including development of the nematode in S. nigrum L., the histopathological response of S. nigrum L. to M. enterolobii, and the host suitability of S. nigrum L., were studied. The M. enterolobii soil population density was evaluated before and after S. nigrum L. planting. Species identification revealed that it was M. enterolobii infection. Developmental observation indicated that juveniles of M. enterolobii developed fast in S. nigrum L., establishing feeding sites by 5 days after inoculation (DAI) and forming obvious egg masses on the root at 25 DAI. Histopathological observation showed the typical susceptible response of S. nigrum L., including giant cells with thick cell walls, uniformly dense cytoplasm, and less vacuolation, mainly inside the vascular cylinder. Host suitability assays suggested that S. nigrum L. is a good host for M. enterolobii with an average reproduction factor (RF) of 48.04 ± 14.71. Population densities assays revealed that S. nigrum L. increased the population density of M. enterolobii for two consecutive years from 0.48 ± 0.25 and 0.53 ± 0.31 J2/cm3 to 1.33 ± 0.16 and 1.56 ± 0.43 J2/cm3 of soil. These results indicated that M. enterolobii could reproduce well by infecting S. nigrum L. during the fallow season, and it increased the population base of M. enterolobii to the next season during vegetable production, which suggested a novel direction for the control of root-knot nematodes by controlling weeds as transitional hosts of M. enterolobii in the fallow season. [ABSTRACT FROM AUTHOR]

The cucurbit vegetable chieh-qua (Benincasa hispida var. chieh-qua How) is an important crop in South China and southeast Asian countries. Viral diseases cause substantial loss of chieh-qua yield. To identify the viruses that affect chieh-qua in China, ribosomal RNA-depleted total RNA sequencing was performed using chieh-qua leaf samples with typical viral symptoms. The virome of chieh-qua comprises four known viruses (melon yellow spot virus (MYSV), cucurbit chlorotic yellows virus (CCYV), papaya ringspot virus (PRSV) and watermelon silver mottle virus (WSMoV) and two novel viruses: cucurbit chlorotic virus (CuCV) in the genus Crinivirus and chieh-qua endornavirus (CqEV) in the genus Alphaendornavirus. The complete genomes of the two novel viruses in chieh-qua and three other isolates of CuCV in pumpkin, watermelon and cucumber were determined and the recombination signals of pumpkin and watermelon isolates of CuCV were detected. A reverse transcriptase PCR indicated that the dominant viruses of chieh-qua in Hainan are MYSV (66.67%) and CCYV (55.56%), followed by CuCV (27.41%), WSMoV (7.41%), cucumber mosaic virus (8.15%), zucchini yellow mosaic virus (6.67%), PRSV (6.67%) and CqEV (35.56%). Our findings support diagnostic and prevalence studies of viruses infecting chieh-qua in China, enabling sustainable control strategies for cucurbit viruses worldwide. [ABSTRACT FROM AUTHOR]

The viromic profile of Polyscias balfouriana cv. Marginata, a perennial woody and ornamental plant, was determined using ribosomal RNA-depleted total RNA (rRNA-depleted totRNA) sequencing. Five viruses (i.e., polyscias mosaic virus, PoMV; one potential novel rhabdovirus; and three novel viruses of Betaflexiviridae and Closteroviridae) were detected and prevalence-surveyed in Hainan province, China. The genomes of polyscias capillovirus 1 (PCaV-1) and polyscias citrivirus 1 (PCiV-1) of family Betaflexiviridae were completed, and the genomes of polyscias crinivirus 1 (PCrV-1) of Closteroviridae were nearly completed lacking the 5′ and 3′ termini. PCaV-1 shares 68% genome nucleotide (nt) identity and 66% replicase (Rep) amino acid (aa) identity with homologues in apple stem grooving virus (ASGV). PCiV-1 shares 65% genome nt identity and 64% Rep aa identity with homologs in citrus leaf blotch virus (CLBV). Meeting the species demarcation criteria, PCaV-1 and PCiV-1 were considered to be new species in genera Capillovirus and Citrivirus, respectively. PCrV-1 shares high genome nt identity (62%), heat shock protein 70-like protein (HSP70h) and RNA-dependent RNA polymerase (RdRp) aa identity (78–80%) with homologues in tomato chlorosis virus (ToCV). We tentatively consider PCrV-1 to be an unclassified member of the Crinivirus genus. PoMV, PCaV-1, PCiV-1, and PCrV-1 are the prevalent viruses with >73% occurrence in the Xinglong Tropical Botanical Garden, Hainan, China. [ABSTRACT FROM AUTHOR]

Areca palm, rubber tree, and coffee are always planted adjacent to each other or intercropped with each other, and Colletotrichum siamense was found to be the dominant species of Colletotrichum from these crops in Hainan, China. To study the population structure, pathogenicity, and fungicide sensitivity of C. siamense from these three crops in Hainan, isolates were first identified by their morphological characteristics and multilocus phylogeny. Then both permutational multivariate analysis of variance (PERMANOVA) and pairwise FST analysis showed that the original host and geographical origin (counties) had significant effects on genetic variation in the C. siamense population, explaining 5.6% and 16.3% of genetic variation, respectively. There were significant genetic differentiations between coffee and rubber tree populations but the genetic differentiation was small (FST = 0.04), while significant differentiations were observed among all populations from different counties except those between Haikou and Chengmai. Pathogenicity analysis using artificial inoculation showed that isolates had significantly higher disease incidence and diseased lesion diameter on wounded leaves than on nonwounded leaves. However, the original host of an isolate and geographical origin did not significantly affect the pathogenicity of the C. siamense populations from these three hosts. In vitro tests showed that there were no significant differences in the sensitivity of C. siamense populations to carbendazim, prochloraz, difenoconazole, and propiconazole from different original hosts and geographical origins. The present study suggests that host specialization of C. siamense has not occurred yet in coffee, rubber tree, and areca palm. [ABSTRACT FROM AUTHOR]

Black pepper (Piper nigrum L.) is one of the most ancient spice crops in the world. Hainan Province is the largest black pepper‐producing region in China. Viral disease is one of the main factors affecting black pepper. However, there are rarely studies on black pepper viral disease in China. We performed a survey in five major black pepper‐growing counties (Qionghai, Wenchang, Wanning, Haikou and Ding'an) of Hainan Province and collected 589 samples, with virus‐like symptoms from 2014 to 2019. Various viruses were identified including cucumber mosaic virus (CMV), piper yellow mottle virus (PYMoV), Piper DNA virus 1 (PDV‐1) and Piper DNA virus 2 (PDV‐2) using small RNA deep sequencing. The RT‐PCR screening of field samples indicated three types of infection: CMV alone (5.56%), PYMoV + PDV‐1 + PDV‐2 (25.00%) and PYMoV + CMV +PDV‐1 + PDV‐2 (69.44%). The data suggested that PYMoV might be the main pathogen causing virus diseases of black pepper. Two complete genome sequences of PYMoV were obtained. Phylogenetic analysis showed that PYMoV isolates from China were placed in a branch distinct from PYMoV isolates from India. To our knowledge, this is the first report of PYMoV, PDV‐1 and PDV‐2 naturally infecting black pepper, and the first genome sequence of PYMoV in China. [ABSTRACT FROM AUTHOR]

Powdery mildew is an important disease of rubber trees worldwide. To assess the effects of temperature and leaf age on conidial germination and disease development, conidia were inoculated onto rubber tree seedlings with leaves at three phenological stages (copper bronze, colour‐changing, and light green) and then incubated at six constant temperatures (10, 15, 20, 25, 30, and 35°C). Leaf age did not affect conidial germination (p =.296) whilst temperature did (p <.0001), although conidia were able to germinate at all tested temperatures. The estimated optimal temperature for conidial germination was 23.2°C. Leaf age, temperature, and their interactions had significant effects on conidial infection and hypha number (p <.0001). At 10 and 35°C, more than 2 and 4 days were needed for infection to complete, respectively, compared to <2, 1, 0.5, and 0.5 days for 15, 20, 25, and 35°C, respectively. Sporulation and mildew symptoms were only observed on those inoculated leaves of all stages at 20 and 25°C, and at the copper bronze stage only at 15°C. The latent period on the copper bronze leaves at 15°C was longer (9 days) than at 20 and 25°C (4 days). The latent period at 20 and 25°C increased from 4 to 7 days as the leaf development stage increased from copper bronze to light green. Therefore, temperature affected germination and postgermination growth of rubber tree powdery mildew, whereas leaf age primarily affected postgermination growth of the pathogen. [ABSTRACT FROM AUTHOR]

Acute myeloid leukemia (AML) is the second most common type of leukemia worldwide. It was previously reported that expression of the long noncoding RNA LOC285758 is positively associated with AML cell proliferation, but the underlying mechanisms have not previously been reported. Here, we report that LOC285758 expression is higher in clinical AML blood samples and cultured AML cells. miR‐204‐5p was confirmed to be a target gene of LOC285758 by bioinformatics analysis and luciferase assay. LOC285758 overexpression promoted AML cell viability and invasion abilities, which were effectively inhibited by miR‐204‐5p overexpression; moreover, miR‐204‐5p overexpression also regulated the expression of E‐cadherin, N‐cadherin and Twist1. The data also showed that increased LOC285758 expression could effectively suppress the earlier effects of miR‐204‐5p on AML cells. Our findings suggest that targeting of miR‐204‐5p by LOC285758 promotes the cell viability and invasion of AML cells, and thus LOC285758 may have potential as a therapeutic target for AML treatment. [ABSTRACT FROM AUTHOR]

We previously reported that oroxylin A, a γ-aminobutyric acid A (GABA) receptor antagonist, ameliorates drugs-induced memory impairments. We synthesized several oroxylin A derivatives in efforts to find a substance that has pro-cognitive effects as well as improves sensorimotor gating. The aim of the present study is to investigate the effect of a novel oroxylin A derivative, 5,7-dihydroxy-6-methoxy-2(4-phenoxyphenyl)-4 H-chromene-4-one (DMPC), on pharmacological models of schizophrenia, which exhibit memory impairment and sensorimotor gating deficit. Memory impairment was induced by scopolamine, a muscarinic receptor antagonist, or MK-801, an N-methyl- d-aspartate receptor antagonist. Sensorimotor gating deficits were induced by MK-801 and measured by prepulse inhibition (PPI) of the acoustic startle response task. DMPC treatment (20 mg/kg) significantly attenuated scopolamine- or MK-801-induced memory impairment and it even enhanced cognitive performance of normal animals. Furthermore, DMPC significantly ameliorated MK-801-induced PPI deficits in the acoustic startle response task. In an in vitro study, DMPC (20 μM) inhibited intracellular Cl influx induced by muscimol, a selective GABA receptor agonist. These results suggest that DMPC would be a potential candidate for alleviating cognitive dysfunction and sensorimotor gating deficits in schizophrenia, and that its effects may be mediated, in part, via blockade of the GABAergic neurotransmitter system. [ABSTRACT FROM AUTHOR]

In July 2008, Stylosanthes guianensis with witches'-broom symptoms and Stylosanthes capitata with yellows symptoms were observed in Hainan Province, China. From the symptomatic S. guianensis, the phytoplasma-specific 16S rRNA gene fragment of 1.4 kb was amplified by a direct PCR, and a fragment of 16S rRNA gene of 1.2 kb was obtained from the symptomatic Stylosanthes capitata by a nested PCR. Sequencing results and NCBI BLASTn analysis showed that the two phytoplasmas belonged to group 16SrII. Polygenetic analysis and virtual RFLP classified the two phytoplasmas into subgroup 16SrII-A. [ABSTRACT FROM AUTHOR]

Abstract: A series of 1,5-diarylimidazoles with 4-methylsulfonylphenyl group were prepared and evaluated for the inhibitory activities against COX-2 catalyzed PGE2 production from LPS-induced RAW 264.7 cells. Most of synthesized 1,5-diarylimidazoles exhibited strong inhibitory activities regardless of the position of the 4-methylsulfonylphenyl group. The 1,5-diarylimidazoles with a halogen atom (3c–3h, 3n–3p) gave mostly excellent inhibitory activities regardless of the position and species of the halogen atom. Whereas the 1,5-diarylimidazoles with two fluorine atoms (3k, 3l, 3r, 3s) showed rather reduced inhibitory activities. [Copyright &y& Elsevier]

Codiaeum variegatum is a valuable ornamental plant with distinct bright yellowing and golden spots on dark green leaves, which resemble virus symptoms. To investigate the factors, especially viral agents, associated with the variegated leaf color of Codiaeum variegatum, we performed virome profiling of a single C. variegatum 'Gold Dust' leaf sample collected from Hainan, China using ribosomal RNA-depleted total RNA sequencing on an Illumina NovaSeq 6000 platform. Two novel viruses, with two variants each, belonging to the family Closteroviridae were detected and characterized: Croton golden spot-associated virus C variants 1 and 2 (CGSaVC-v1, and CGSaVC-v2) of the genus Crinivirus and Croton golden spot-associated virus A variants 1 and 2 (CGSaVA-v1 and CGSaVA-v2) of the genus Ampelovirus. Transmission electron microscopy showed long, flexuous, filamentous virus particles approximately 15 nm in diameter and 760-770 nm in length. Molecular screening of ninety-seven variegated individual plant leaves showed a high prevalence of CGSaVA-v1 (90.7%), CGSaVA-v2 (75.3 %), CGSaVC-v1 (70.1%), and CGSaVC-v2 (47.4%), while asymptomatic leaves near the meristem tip were mostly free of the target viruses. To our knowledge, this is the first study to demonstrate the significant association between closterovirids and the golden spots. The findings provide novel insights into the genetic diversity of the family Closteroviridae and inform future germplasm conservation and new cultivar development of Codiaeum Variegatum.

Phytoplasmas are a group of plant prokaryotic pathogens distributed worldwide. To comprehensively reveal the diversity of the pathogens and the diseases they cause on Hainan, a tropical island with abundant biodiversity in China, a survey of phytoplasmal diseases was performed from 2009 to 2022. Herein, molecular identification and genetic analysis were conducted based on the conserved genes of phytoplasmas. The results indicated that phytoplasmas could be detected in 138 samples from 18 host plants among 215 samples suspected to be infected by the pathogens. The phytoplasma strains from 27 diseased samples of 4 host plants belonged to the 16SrI group and the strains from 111 samples of 14 hosts belonged to the 16SrII group. Among them, 12 plants, including important tropical cash crops such as Phoenix dactylifera , cassava, sugarcane, and Piper nigrum , were first identified as hosts of phytoplasmas on Hainan Island. Based on BLAST and i PhyClassifier analyses, seven novel 16Sr subgroups were proposed to describe the relevant phytoplasma strains, comprising the 16SrI-AP, 16SrI-AQ, and 16SrI-AR subgroups within the 16SrI group and the 16SrII-Y, 16SrII-Z, 16SrII-AB, and 16SrII-AC subgroups within the 16SrII group. Genetic variation and phylogenetic analysis indicated that the phytoplasma strains identified in this study and those reported previously on Hainan Island mainly belong to four 16Sr groups (including I, II, V, and XXXII) and could infect 44 host plants, among which the 16SrI and 16SrII groups were the prevalent 16Sr groups associated with 43 host plant species. The diversity of host plants infected by the phytoplasmas made it difficult to monitor and control their related diseases. Therefore, strengthening inspection and quarantine during the introduction and transit of the related phytoplasmal host crops would effectively curb the spread and prevalence of the phytoplasmas and their related lethal diseases., Competing Interests: The author(s) declare no conflict of interest.

Root-knot nematodes ( Meloidogyne spp.) are the most economically damaging group of plant-parasitic nematodes. They are considered to be a major constraint of pepper ( Capsicum annuum L.) crops worldwide. In China, Hainan Island is the main producer of pepper, where the climatic conditions and cropping patterns are favorable for infection by Meloidogyne spp. In this study, we conducted a detailed investigation of the occurrence, severity, and population distribution of root-knot nematodes infesting pepper throughout Hainan Island. We also tested the level of resistance to M. enterolobii and M. incognita of the common pepper cultivars in Hainan. Our results showed that root-knot nematodes belonging to M. enterolobii , M. incognita , and M. javanica were found in Hainan, and the dominant population was M. enterolobii , which is the predominant species in the tropical area. Notably, all the pepper cultivars in this study were highly susceptible to M. enterolobii , which is probably a reason for its rapid spread throughout Hainan. The pepper cultivars exhibited different levels of resistance to M. incognita . This study promotes the comprehensive understanding of the root-knot nematode distribution and host resistance level of Meloidogyne in Hainan, which will guide the effective control of root-knot nematodes., Competing Interests: The author(s) declare no conflict of interest.

Colletotrichum siamense was demonstrated as the dominant species among Colletotrichum spp. that infected rubber tree, areca palm, and coffee in Hainan, China. However, the extent of genetic differentiation within the species C. siamense in relation to geographical regions and host species is not known. In this study, 112 C. siamense isolates were genotyped with 12 microsatellite markers. In total, there were 99 multilocus genotypes. Results from permutational multivariate analysis of variance and analysis of molecular variance indicated that there was no significant genetic differentiation between fungal populations with respect to host, location (county), and year. Discriminant analysis of principal components and STRUCTURE analysis showed that C. siamense isolates grouped into three clusters; further analysis confirmed that there were significant ( P < 0.001) genetic differences among the three clusters. However, each cluster had isolates from different hosts, counties, or years, supporting the lack of genetic differentiation with respect to host, county, and year. Statistical analyses of allelic associations indicated some evidence for recombination within the populations defined on the basis of host or county. The present findings provide insights into the genetic structure of C. siamense on the three perennial host species in Hainan and suggest that the disease on these three crops can be effectively considered as one disease and, hence, needs to be controlled simultaneously in mixed plantations.

Viral diseases are one of the main categories of diseases that cause substantial yield losses in black pepper. Disease symptoms in black pepper are generally complex and are often caused by both known and undescribed viruses. To identify and clarify the etiology of viral diseases in black pepper in Hainan, China, we conducted high-throughput sequencing (HTS) by targeting purified double-stranded RNA (dsRNA) and ribosomal RNA depleted total RNA (rRNA-depleted totRNA). Analysis of the data revealed the presence of one known virus, piper yellow mottle virus (PYMoV), and three newly identified viruses: black pepper virus F (BPVF) in the genus Fabavirus , black pepper virus E (BPVE) in the genus Enamovirus , and black pepper virus B (BPVB) in the genus Badnavirus . The dominant viruses in P. nigrum sampled in Hainan are PYMoV, with an incidence of 100%, followed by BPVF (84%, 133 of 158) and BPVB (66%, 105 of 158). Mechanical inoculation of sap extracts from source plants containing PYMoV, BPVF, and BPVB gave negative results on both herbaceous and woody host plants 60 days postinoculation (dpi). BPVF and PYMoV were successfully transmitted to virus-free seedlings of black pepper through bark grafting, while BPVB was experimentally undetectable up to 150 dpi. Seed transmission experiments showed that no target viruses were present in all 59 germinated seedlings. This study provides information on diagnosis, prevalence, and transmission of black-pepper-associated viruses.

Genus Colletotrichum is one of the most important genera of plant-pathogenic fungi affecting numerous species, particularly tropical and subtropical crops and fruit trees. In this study, 43 Colletotrichum strains were isolated from areca palm leaves with anthracnose symptoms in 11 areca palm plantations in eight counties of Hainan, China. Based on the morphology, phylogenetic analysis of six loci (internal transcribed spacer, actin, chitin synthase 1, glyceraldehyde-3-phosphate dehydrogenase, β-tubulin, and mating type locus MAT1-2), and pathogenicity tests, eight Colletotrichum species were distinguished, comprising five previously known species ( C. cordylinicola , C. fructicola , C. gloeosporioides , C. siamense , and C. tropicale ), one unidentified Colletotrichum species, a new species ( C. arecicola ) in the gloeosporioides species complex, and C. karstii in the boninense species complex. C. siamense was the most common species found in areca palm in Hainan, followed by C. arecicola . Pathogenicity tests showed that all eight species could cause anthracnose symptoms on areca palm leaves using a wound inoculation method and that the isolates from the gloeosporioides species complex caused larger lesions than the isolates from the boninense species complex. Further research is needed to understand the epidemiology of these pathogenic species on areca palm in order to develop management strategies.

Colletotrichum gloeosporioides and C. acutatum have been reported to be causal agents of anthracnose disease of rubber tree. Recent investigations have shown that both C. gloeosporioides and C. acutatum are species complexes. The identities of Colletotrichum species causing anthracnose disease of rubber tree in Hainan, China, are unknown. In this study, 106 isolates obtained from rubber tree with symptoms of anthracnose were collected from 12 counties of Hainan and identified at the species complex level based on the ITS sequences and colony morphologies. Seventy-four isolates were identified as C. gloeosporioides species complex and the other 32 isolates as C. acutatum species complex. Forty-two isolates were selected for further multilocus phylogenetic analyses in order to identify the isolates to the species level. Twenty-six isolates from the C. gloeosporioides species complex were characterized for partial sequences of seven gene regions (ACT, TUB2, CHS-1, GAPDH, ITS, ApMat, and GS), and the other 16 isolates from the C. acutatum species complex for five gene regions (ACT, TUB2, CHS-1, GAPDH, and ITS). Three species were identified: C. siamense and C. fructicola from the C. gloeosporioides species complex, and a new species C. wanningense from the C. acutatum species complex. Artificial inoculation of rubber tree leaves confirmed the pathogenicity of the three species. The present study improves the understanding of species causing anthracnose on rubber tree and provides useful information for the effective control of the disease.

Colletotrichum gloeosporioides and C. acutatum species complexes are causal agents of Colletotrichum leaf disease (CLD) of rubber trees worldwide. To determine the geographic distribution of Colletotrichum species complexes associated with CLD of rubber trees in Hainan, China, and their sensitivity to fungicides used in the region, a total of 275 Colletotrichum isolates were collected from 52 rubber tree plantations in 11 counties. These isolates were identified based jointly on morphological characteristics and PCR-based methodology. Of these isolates, 78 and 22% belonged to the C. gloeosporioides species complex (CGSC) and the C. acutatum complex (CASC), respectively. The incidence of CGSC isolates was greater than the CASC in all counties sampled. The incidence of CASC isolates appeared to be lower in the western and central south of Hainan than in other regions. There was no association in their presence at a given plantation between the two species complexes. The in vitro sensitivity of these two species complexes to carbendazim, chlorothalonil, and four demethylation inhibitor (DMI) fungicides (difenoconazole, propiconazole, myclobutanil, and prochloraz) was determined. Carbendazim was effective against CGSC but not against CASC with mean ED 50 values of 0.176 and 2.182 µg/ml, respectively. CASC isolates were more sensitive to difenoconazole, propiconazole, and myclobutanil (mean ED 50 values of 0.177, 0.129, and 1.424 µg/ml, respectively) than CGSC isolates (mean ED 50 values of 0.710, 0.348, and 3.496 µg/ml, respectively). Mean ED 50 values of CGSC against chlorothalonil and prochloraz were 173.341 and 0.035 µg/ml, respectively; corresponding values for CASC were 151.441 and 0.040 µg/ml. These results suggest that prochloraz, propiconazole, and difenoconazole are effective against both species complexes.

Papaya is an important fruit crop cultivated in tropical and subtropical regions. Papaya little leaf (PLL) disease was observed in China. The phytoplasma 16S rRNA gene was detected from symptomatic papaya trees via PCR using phytoplasma universal primers P1/P7 followed by R16F2n/R16R2. No amplification products were obtained from templates of asymptomatic papaya trees. These results indicated a direct association between phytoplasma infection and PLL disease. Comparative and phylogenetic analyses of 16S rRNA gene sequences indicated that the papaya-infecting phytoplasmas under study belonged to the peanut witches' broom phytoplasma group (16SrII). Genotyping through use of computer-simulated RFLP analysis of 16S rRNA genes and coefficients of RFLP pattern similarities (0.97) reveal that the PLL phytoplasma was placed in a new subgroup. In this article, we describe the molecular characterization of a new phytoplasma associated with PLL disease and propose that the PLL phytoplasma be considered as a novel subgroup, 16SrII-U.