Using machine learning methods to study the tumour microenvironment and its biomarkers in osteosarcoma metastasis.

Background: The long-term prognosis for patients with osteosarcoma (OS) metastasis remains unfavourable, highlighting the urgent need for research that explores potential biomarkers using innovative methodologies. Methods: This study explored potential biomarkers for OS metastasis by analysing data from the Cancer Genome Atlas Program (TCGA) and Gene Expression Omnibus (GEO) databases. The synthetic minority oversampling technique (SMOTE) was employed to tackle class imbalances, while genes were selected using four feature selection algorithms (Monte Carlo feature selection [MCFS], Borota, minimum-redundancy maximum-relevance [mRMR], and light gradient-boosting machine [LightGBM]) based on the gene expression matrix. Four machine learning (ML) algorithms (support vector machine [SVM], extreme gradient boosting [XGBoost], random forest [RF], and k-nearest neighbours [kNN]) were utilized to determine the optimal number of genes for building the model. Interpretable machine learning (IML) was applied to construct prediction networks, revealing potential relationships among the selected genes. Additionally, enrichment analysis, survival analysis, and immune infiltration were performed on the featured genes. Results: In DS1, DS2, and DS3, the IML algorithm identified 53, 45, and 46 features, respectively. Using the merged gene set, we obtained a total of 79 interpretable prediction rules for OS metastasis. We subsequently conducted an in-depth investigation on 39 crucial molecules associated with predicting OS metastasis, elucidating their roles within the tumour microenvironment. Importantly, we found that certain genes act as both predictors and differentially expressed genes. Finally, our study unveiled statistically significant differences in survival between the high and low expression groups of TRIP4, S100A9, SELL and SLC11A1, and there was a certain correlation between these genes and 22 various immune cells. Conclusions: The biomarkers discovered in this study hold significant implications for personalized therapies, potentially enhancing the clinical prognosis of patients with OS.

Response of the symbiotic microbial community of Dioscorea opposita Thunb. cv. Tiegun to root-knot nematode infection.

Yam is an important medicinal and edible dual-purpose plant with high economic value. However, nematode damage severely affects its yield and quality. One of the major effects of nematode infestations is the secondary infection of pathogenic bacteria or fungi through entry wounds made by the nematodes. Understanding the response of the symbiotic microbial community of yam plants to nematodes is crucial for controlling such a disease. In this study, we investigated the rhizosphere and endophytic microbiomes shift after nematode infection during the tuber expansion stage in the Dioscorea opposita Thunb. cv. Tiegun yam. Our results revealed that soil depth affected the abundance of nematodes, and the relative number of Meloidogyne incognita was higher in the diseased soil at a depth of 16-40 cm than those at a depth of 0-15 cm and 41-70 cm. The abundance of and interactions among soil microbiota members were significantly correlated with root-knot nematode (RKN) parasitism at various soil depths. However, the comparison of the microbial alpha diversity and composition between healthy and diseased rhizosphere soil showed no difference. Compared with healthy soils, the co-occurrence networks of M. incognita-infested soils included a higher ratio of positive correlations linked to plant health. In addition, we detected a higher abundance of certain taxonomic groups belonging to Chitinophagaceae and Xanthobacteraceae in the rhizosphere of RKN-infested plants. The nematodes, besides causing direct damage to plants, also possess the ability to act synergistically with other pathogens, especially Ramicandelaber and Fusarium, leading to the development of disease complexes. In contrast to soil samples, RKN parasitism specifically had a significant effect on the composition and assembly of the root endophytic microbiota. The RKN colonization impacted a wide variety of endophytic microbiomes, including Pseudomonas, Sphingomonas, Rhizobium, Neocosmospora, and Fusarium. This study revealed the relationship between RKN disease and changes in the rhizosphere and endophytic microbial community, which may provide novel insights that help improve biological management of yam RKNs.

How to Choose the Appropriate Posterior Slope Angle Can Lead to Good Knee Joint Function Recovery in Total Knee Arthroplasty?

Objective: In this study, we aim to examine the effects of osteotomy under varying posterior slope angles on knee joint function recovery following knee arthroplasty. Methods: We conducted a retrospective analysis from September 2015 to September 2018 on 240 patients who underwent knee arthroplasty three years previously. The study participants were categorized based on changes in the angle of the posterior slope before and after surgery: Group 1, > 5°; Group 2, 3°-5°; Group 3, 0°-3°; Group 4, -3°-0°; Group 5, < -3°. All participants were affected with knee osteoarthritis. The Knee Society Clinical Rating System (KSS) knee function score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) knee function score, Visual Analogue Scale (VAS) pain score, and postoperative complications were measured 3 years after surgery. Results: The level of pain experienced by the patients decreased significantly than before, with pain scores ranging from 1.0-3.0, and there was a statistical difference between groups (H = 93.400, P < 0.001). The KSS score increased, with group 5 having the lowest median score of 78.0 and group 2 having the highest median score of 97.0, and there was a statistical difference between groups (H = 164.460, P < 0.001). The WOMAC score was reduced, with the median score being 24.0, 11.0, 14.0, 20.0, and 26.0, in the five groups, respectively. Group 5 had the highest score, while Group 2 had the lowest score, and there was a statistically significant difference between groups (H = 164.223, P < 0.001). No symptoms such as periprosthetic femoral fracture, prosthetic loosening, or pad wear were detected in patients postoperatively. Conclusion: Osteotomy at various posterior slope angles in total knee arthroplasty impacts postoperative knee function rehabilitation. An excessive increase or decrease in angle can have an impact on the postoperative recovery of knee function.

Identification of BBX gene family and its function in the regulation of microtuber formation in yam.

BBX proteins play important roles in all of the major light-regulated developmental processes. However, no systematic analysis of BBX gene family regarding the regulation of photoperiodic microtuber formation has been previously performed in yam. In this study, a systematic analysis on the BBX gene family was conducted in three yam species, with the results, indicating that this gene plays a role in regulating photoperiodic microtuber formation. These analyses included identification the BBX gene family in three yam species, their evolutionary relationships, conserved domains, motifs, gene structure, cis-acting elements, and expressional patterns. Based on these analyses, DoBBX2/DoCOL5 and DoBBX8/DoCOL8 showing the most opposite pattern of expression during microtuber formation were selected as candidate genes for further investigation. Gene expression analysis showed DoBBX2/DoCOL5 and DoBBX8/DoCOL8 were highest expressed in leaves and exhibited photoperiod responsive expression patterns. Besides, the overexpression of DoBBX2/DoCOL5 and DoBBX8/DoCOL8 in potato accelerated tuber formation under short-day (SD) conditions, whereas only the overexpression of DoBBX8/DoCOL8 enhanced the accelerating effect of dark conditions on tuber induction. Tuber number was increased in DoBBX8/DoCOL8 overexpressing plants under dark, as well as in DoBBX2/DoCOL5 overexpressing plants under SD. Overall, the data generated in this study may form the basis of future functional characterizations of BBX genes in yam, especially regarding their regulation of microtuber formation via the photoperiodic response pathway.

An investigation into whether changes in the posterior tibial slope affect the outcome of cruciate-retaining total knee arthroplasty by affecting tibiofemoral articular contact kinematics.

Aims: The outcomes of total knee arthroplasty (TKA) are affected by many factors. This study aims to evaluate whether changes in the posterior tibial slope (PTS) affect patients' outcomes after cruciate-retaining TKA by affecting tibiofemoral articular contact kinematics. It was hypothesized that changes in PTS affect the outcomes of PCR TKA by affecting tibiofemoral articular contact kinematics. Methods: A total of 60 knees (30 patients) that underwent posterior cruciate-retaining TKA (with the same size prosthesis) for medial osteoarthritis were assessed preoperatively and one year postoperatively. Before and after TKA, changes in the PTS, as seen on lateral radiographs, were noted. The knees were placed in groups according to these PTS changes (preoperative value - postoperative value): group 1 >3° change and group 2 ≤3° change. Knee kinematics were observed under mid-flexion weight-bearing conditions and were compared between the two groups using the two-dimensional/three-dimensional registration technique. Pain was measured using the visual analog scale, and knee function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Knee Society Score (KSS). Results: Group 2 experienced paradoxical anterior motion of the medial femoral condyle postoperatively, but group 1 did not. A comparison of the results of the TKA between the two groups showed a significant difference in pain using the visual analog scale, and knee function of the KSS and the WOMAC (P < 0.05). The postoperative results were better in group 1 than in group 2. Conclusions: These results suggest that achieving a greater change in the PTS improves outcomes in patients undergoing posterior cruciate-retaining TKA because it reduces the paradoxical motion of the medial femoral condyle.

First Report of Root-Knot Nematode (Meloidogyne incognita) on Dioscorea opposita in Henan Province, China.

Dioscorea opposita is an annual twining plant in China that is used for consumption and medicinal purposes. The planting area of D. opposita is near 500,000 hectares in China, mainly in Shangdong, Hebei, Henan, Jiangxi and Yunnan provinces. In August 2021, we observed that some D. opposita plants grew poorly with smaller and chlorotic leaves in Changyuan (35°8'12"N; 114°43'52"E), Henan Province, China. Galls with hook-shaped roots and tuber damage were also observed, typical of root-knot nematode. Thirty tubers were randomly collected and 60% were infested with root-knot nematodes. During a disease survey in Changyuan, the incidences of root-knot nematode damage were 31.5%, 21%, and 18% in three fields (0.33, 0.67, and 4 ha, respectively) at harvest. The average tuber length of infected plants was decreased by 65.8%, and the average weight was decreased by 70.1% compared to the healthy plants. Males, females, second-stage juveniles (J2s), and eggs were extracted from individual diseased tubers from the three fields for morphological identification. Females were white, pear-shaped with a projecting neck. Males showed a trapezoidal labial region with prominent stylet knobs, including a high head cap which had a stepped outline and was centrally concave in lateral view. Morphological measurements are described in the supplementary material. All data and descriptions conformed to the morphological characteristics of Meloidogyne incognita. Genomic DNA was extracted from J2s (n=9) using PCR lysis buffer, and used for PCR amplification of the sequence characterized amplified region (SCAR) markers specific for M. incognita. Two pairs of the SCAR primers, Mi-F/Mi-R, and Inc-K14-F/Inc-K14-R, were used to diagnose whether these nematodes from D. opposita were M. incognita (Meng et al. 2004; Randig et al. 2002). The PCR produced expected amplification products of 955 and 399 bp, confirming the nematode to be M. incognita. Primers specific for M. arenaria (Far/Rar) and M. javanica (Fjav/Rjav) were used but failed to amplify fragments (Randig et al. 2002; Zijlstra et al. 2000). The obtained PCR fragments were sequenced and deposited in GenBank (accession no. OQ420602.1, OQ427638.1). They showed 99.9 and 100% identity to the available GenBank M. incognita sequence (accession no. MK410954.1, ON861825.1), respectively. A pathogenicity test was conducted in greenhouse conditions. Bulbils of D. opposita were sown in the pots filled with 2,000 ml of autoclaved soil mixture (loamy soil/sand, 1:1). One month later, 15 seedlings (five to six leaf stage) were inoculated with 1,000 M. incognita J2s individually. Five plants without nematode inoculation were used as the control. Two months after inoculation, all of the inoculated roots had galling symptoms similar to those observed in the field, and 100% of root system tissues had galls. The root gall index was ~6 according to a 0 to 10 RKN damage rating scale (Poudyal et al. 2005). No symptoms were found on the control plants. The nematodes were reisolated from root tissue and identified. M. incognita has a broad host range in many species of economic importance including Salvia miltiorrhiza (Wen et al. 2023), Ipomoea batatas (Maleita et al. 2022), and Zea mays (López-Robles et al. 2013). So far, M. incognita has been reported in D. alata and D. rotundata in Africa (Onkendi et al. 2014). To our best knowledge, this is the first record of M. incognita on D. opposita in Henan Province, China. With the increased planting area of D. opposita in China, root-knot nematodes are becoming more serious and reducing tuber production, with yield losses more than 60%. This identification is a preliminary step in developing effective disease management schemes. Declaration of interest The authors declare no conflict of interest. Funding This work was financially supported by the Key Scientific Research Projects of Higher Education Institutions of Henan Province (21A180013), China Agriculture Research System (CARS-21), The Zhongyuan high level talents special support plan-Science and Technology Innovation Leading Talents (224200510011) and Science and Technology Research Project of Henan Province (222102310211). References López-Robles, J., et al. 2013. Plant Dis. 97:694. https://doi.org/10.1094/PDIS-07-12-0674-PDN. Maleita, C., et al. 2022. Plant Dis. 106:2536. https://doi.org/10.1094/PDIS-12-21-2680-PDN. Meng, Q. P., et al. 2004. Acta Phytopathol. Sinica 34:204. https://doi.org/10.13926/j.cnki.apps.2004.03.003. Onkendi, E. M., et al. 2014. Plant Pathol. 63:727. https://doi.org/10.1111/ppa.12202. Poudyal, D. S., et al. 2005. Australas. Plant Pathol. 34:181. https://doi.org/10.1071/AP05011. Randig, O., et al. 2002. Genome 45:862. https://doi.org/10.1139/g02-054. Wen, Y., et al. 2023. Plant Dis. Accepted. https://doi.org/10.1094/PDIS-05-22-0997-PDN. Zijlstra, C., et al. 2000. Nematology 2:847. https://doi.org/10.1163/156854100750112798.

Improving Air Quality by Nitric Oxide Consumption of Climate-Resilient Trees Suitable for Urban Greening.

Nitrogen oxides (NOx), mainly a mixture of nitric oxide (NO) and nitrogen dioxide (NO2), are formed by the reaction of nitrogen and oxygen compounds in the air as a result of combustion processes and traffic. Both deposit into leaves via stomata, which on the one hand benefits air quality and on the other hand provides an additional source of nitrogen for plants. In this study, we first determined the NO and NO2 specific deposition velocities based on projected leaf area (sV d) using a branch enclosure system. We studied four tree species that are regarded as suitable to be planted under predicted future urban climate conditions: Carpinus betulus, Fraxinus ornus, Fraxinus pennsylvanica and Ostrya carpinifolia. The NO and NO2 sVd were found similar in all tree species. Second, in order to confirm NO metabolization, we fumigated plants with 15NO and quantified the incorporation of 15N in leaf materials of these trees and four additional urban tree species (Celtis australis, Alnus spaethii, Alnus glutinosa, and Tilia henryana) under controlled environmental conditions. Based on these 15N-labeling experiments, A. glutinosa showed the most effective incorporation of 15NO. Third, we tried to elucidate the mechanism of metabolization. Therefore, we generated transgenic poplars overexpressing Arabidopsis thaliana phytoglobin 1 or 2. Phytoglobins are known to metabolize NO to nitrate in the presence of oxygen. The 15N uptake in phytoglobin-overexpressing poplars was significantly increased compared to wild-type trees, demonstrating that the NO uptake is enzymatically controlled besides stomatal dependence. In order to upscale the results and to investigate if a trade-off exists between air pollution removal and survival probability under future climate conditions, we have additionally carried out a modeling exercise of NO and NO2 deposition for the area of central Berlin. If the actually dominant deciduous tree species (Acer platanoides, Tilia cordata, Fagus sylvatica, Quercus robur) would be replaced by the species suggested for future conditions, the total annual NO and NO2 deposition in the modeled urban area would hardly change, indicating that the service of air pollution removal would not be degraded. These results may help selecting urban tree species in future greening programs.

Phytoglobin overexpression promotes barley growth in the presence of enhanced level of atmospheric nitric oxide.

To investigate the effect of high atmospheric NO concentrations on crop plants and the role of phytoglobins under these conditions, we performed a long-term study on barley 'Golden Promise' wild type (WT), class 1 phytoglobin knockdown (HvPgb1.1-) and class 1 phytoglobin overexpression (HvPgb1.1+) lines. Plants were cultivated with nitrogen-free nutrient solution during the entire growth period and were fumigated with different NO concentration (ambient, 800, 1500, and 3000 ppb). Analysis of fresh weight, stem number, chlorophyll content, and effective quantum yield of PSII showed that NO fumigation promoted plant growth and tillering significantly in the HvPgb1.1+ line. After 80 d of NO fumigation, dry matter weight, spikes number, kernel number, and plant kernel weight were significantly increased in HvPgb1.1+ plants with increasing NO concentration. In contrast, yield decreased in WT and HvPgb1.1- plants the higher the NO level. Application of atmospheric 15NO and 15NO2 demonstrated NO specificity of phytoglobins. 15N from 15NO could be detected in RNA, DNA, and proteins of barley leaves and the 15N levels were significantly higher in HvPgb1.1+ plants in comparison with HvPgb1.1- and WT plants. Our results demonstrate that overexpression of phytoglobins allows plants to more efficiently use atmospheric NO as N source.

Nitric oxide-fixation by non-symbiotic haemoglobin proteins in Arabidopsis thaliana under N-limited conditions.

Nitric oxide (NO) is an important signalling molecule that is involved in many different physiological processes in plants. Here, we report about a NO-fixing mechanism in Arabidopsis, which allows the fixation of atmospheric NO into nitrogen metabolism. We fumigated Arabidopsis plants cultivated in soil or as hydroponic cultures during the whole growing period with up to 3 ppmv of NO gas. Transcriptomic, proteomic and metabolomic analyses were used to identify non-symbiotic haemoglobin proteins as key components of the NO-fixing process. Overexpressing non-symbiotic haemoglobin 1 or 2 genes resulted in fourfold higher nitrate levels in these plants compared with NO-treated wild-type. Correspondingly, rosettes size and weight, vegetative shoot thickness and seed yield were 25, 40, 30, and 50% higher, respectively, than in wild-type plants. Fumigation with 250 ppbv 15 NO confirmed the importance of non-symbiotic haemoglobin 1 and 2 for the NO-fixation pathway, and we calculated a daily uptake for non-symbiotic haemoglobin 2 overexpressing plants of 250 mg N/kg dry weight. This mechanism is probably important under conditions with limited N supply via the soil. Moreover, the plant-based NO uptake lowers the concentration of insanitary atmospheric NOx, and in this context, NO-fixation can be beneficial to air quality.

Photoprotection mechanism in the 'Fuji' apple peel at different levels of photooxidative sunburn.

The xanthophyll cycle, flavonoid metabolism, the antioxidant system and the production of active oxygen species were analyzed in the peel of 'Fuji' apples re-exposed to sunlight after extended periods of fruit bagging treatment, resulting in different levels of photooxidative sunburn. After re-exposing bagged fruits to sunlight, the production of active oxygen species and the photoprotective capacity in apple peels were both significantly enhanced. As sunburn severity increased, the concentration of hydrogen peroxide increased, while xanthophyll cycle pool size decreased. For the key genes involved in flavonoid synthesis, expressions of MdMYB10 and MdPAL were upregulated, whereas the expressions of MdCHS, MdANS, MdFLS and MdUFGT were downregulated in sunburnt fruit peel. Correspondingly, concentrations of both quercetin-3-glycoside and cyanidin-3-galactoside decreased. Total ascorbate concentrations decreased as sunburn severity increased, with the decrease being faster for oxidized than for reduced ascorbate. Transcription levels of MdGMP, MdGME, MdGGP, MdGPP, MdGalDH and MdGalLDH, the genes involved in ascorbate synthesis, were similar in non-sunburnt and sunburnt fruit peels, whereas activities of l-galactose dehydrogenase and l-galactono-1,4-lactone dehydrogenase decreased in severely sunburnt peel. Although activities of superoxide dismutase and ascorbate peroxidase increased, the activities of monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase decreased as sunburn severity increased. In summary, the occurrence of photooxidative sunburn in 'Fuji' apple peel is closely associated with a relatively lower xanthophyll cycle pool size, reduced levels of ascorbate reduction and synthesis and reduced flavonoid synthesis. Our data are consistent with the idea that ascorbate plays a key role in protecting apple fruit from photooxidative sunburn.

Reactive oxygen species produced via plasma membrane NADPH oxidase regulate anthocyanin synthesis in apple peel.

MAIN CONCLUSION: Solar ultraviolet irradiation regulates anthocyanin synthesis in apple peel by modulating the production of reactive oxygen species via plasma membrane NADPH oxidase instead of other pathways. The synthesis of anthocyanin in apple peels is dependent upon solar irradiation. Using 3-mm commercial glass to attenuate solar UV-A and UV-B light, we confirmed that solar UV irradiation regulated anthocyanin synthesis in apple peels after exposing previously bagged fruit to sunlight. During sunlight exposure, UV attenuation did not affect the expression of MdHY5, MdCOP1, or MdCRY2, but significantly lowered plasma membrane NADPH oxidase activity and superoxide anion concentrations. UV attenuation also reduced the expression levels of MdMYB10, MdPAL, MdCHS, MdF3H, MdDFR, MdANS and MdUFGT1, UDP-glycose:flavonoid 3-O-glycosyltransferase (UFGT) activity, and local concentrations of anthocyanin and quercetin-3-glycoside. In contrast, exogenous application of hydrogen peroxide could enhance anthocyanin and quercetin-3-glycoside synthesis. Xanthophyll cycle pool size on a chlorophyll basis was higher but its de-epoxidation was lower under direct sunlight irradiation than that under UV-attenuating conditions. This suggests that reactive oxygen species (ROS) produced in chloroplast are not major contributors to anthocyanin synthesis regulation. Inhibition of plasma membrane NADPH oxidase activity lowered the production of ROS through this mechanism, significantly inhibited the synthesis of anthocyanin, and increased the total production of ROS in apple peel under direct sunlight irradiation, suggesting that ROS produced via plasma membrane NADPH oxidase regulates anthocyanin synthesis. In summary, solar UV irradiation regulated anthocyanin synthesis in apple peels by modulating the production of ROS via plasma membrane NADPH oxidase.

Different biosynthesis patterns among flavonoid 3-glycosides with distinct effects on accumulation of other flavonoid metabolites in pears (Pyrus bretschneideri Rehd.).

Flavonoid biosynthesis profile was clarified by fruit bagging and re-exposure treatments in the green Chinese pear 'Zaosu' (Pyrus bretschneideri Rehd.) and its red mutant 'Red Zaosu'. Two distinct biosynthesis patterns of flavonoid 3-glycosides were found in 'Zaosu' pear. By comparison with 'Red Zaosu', the biosynthesis of flavonoid 3-galactosides and flavonoid 3-arabinosides were inhibited by bagging and these compounds only re-accumulated to a small degree in the fruit peel of 'Zaosu' after the bags were removed. In contrast, the biosynthesis of flavonoid 3-gluctosides and flavonoid 3-rutinosides was reduced by bagging and then increased when the fruits were re-exposed to sunlight. A combination of correlation, multicollinearity test and partial-correlation analyses among major flavonoid metabolites indicated that biosynthesis of each phenolic compound was independent in 'Zaosu' pear, except for the positive correlation between flavonoid 3-rutincosides and flavanols. In contrast with the green pear cultivar, almost all phenolic compounds in the red mutant had similar biosynthesis patterns except for arbutin. However, only the biosynthesis of flavonoid 3-galactosides was relatively independent and strongly affected the synthesis of the other phenolic compounds. Therefore, we propose a hypothesis that the strong accumulation of flavonoid 3-galactosides stimulated the biosynthesis of other flavonoid compounds in the red mutant and, therefore, caused systemic variation of flavonoid biosynthesis profiles between 'Zaosu' and its red mutant. This hypothesis had been further demonstrated by the enzyme activity of UFGT, and transcript levels of flavonoid biosynthetic genes and been well tested by a stepwise linear regression forecasting model. The gene that encodes flavonoid 3-galacosyltransferase was also identified and isolated from the pear genome.

Anthocyanin contributes more to hydrogen peroxide scavenging than other phenolics in apple peel.

The phenolic compounds in apple peel extracts were quantified in the presence of hydrogen peroxide (H2O2) to identify which phenolic compound contributed more to H2O2 scavenging. The results showed that the phenolics extracted from 'Golden Delicious' apple peel had a strong ability for scavenging H2O2. After incubating with H2O2 for 30 min, cyanidin-3-galactoside concentrations in the phenolic extract decreased as H2O2 concentrations increased. In contrast, the concentrations of other phenolic compounds remained unchanged. Exogenous application of H2O2 enhanced the synthesis of phenolics, especially anthocyanin, in 'Golden Delicious' apple peel under sunlight. After incubating the peel extract of H2O2-treated apples in the dark for 30 min, the concentration of cyanidin-3-galactoside significantly decreased to a greater extent than that of other phenolic compounds. Based on these data, anthocyanin is more sensitive to H2O2 and contributes more to H2O2 scavenging than other phenolic compounds.

Genetic mapping of two powdery mildew resistance genes in einkorn (Triticum monococcum L.) accessions.

Powdery mildew is a severe foliar disease for wheat and could cause great yield loss in epidemic years. To explore new powdery mildew resistance genes, two einkorn accessions including TA2033 and M80, both resistant to this disease, were studied for the inheritance of resistance. Each accession possessed a single but different dominant resistance gene that was designated as Mlm2033 and Mlm80, respectively. Marker mapping indicated that they are both linked to Xgwm344 on the long arm of chromosome 7A. To establish their genetic relationship with Pm1 on 7AL, five RFLP markers previously reported to co-segregate with Pm1a were converted to STS markers. Three of them detected polymorphism between the mapping parents and were mapped close to Mlm2033 or Mlm80 or both. Xmag2185, the locus determined by the STS marker derived from PSR680, one of the RFLP markers, was placed less than 2 cM away from them. The allelism test indicated that Mlm2033 and Mlm80 are likely allelic to each other. In addition, through comparative and EST mapping, more markers linked to these two genes were identified. The high density mapping of Mlm2033 and Mlm80 will contribute to map-based cloning of the Pm1 locus. The markers for both genes will also facilitate their transfer to wheat.