Co-expression network analysis and identification of core genes in the interaction between wheat and Puccinia striiformis f. sp. tritici.

The epidemic of stripe rust, caused by the pathogen Puccinia striiformis f. sp. tritici (Pst), would reduce wheat (Triticum aestivum) yields seriously. Traditional experimental methods are difficult to discover the interaction between wheat and Pst. Multi-omics data analysis provides a new idea for efficiently mining the interactions between host and pathogen. We used 140 wheat-Pst RNA-Seq data to screen for differentially expressed genes (DEGs) between low susceptibility and high susceptibility samples, and carried out Gene Ontology (GO) enrichment analysis. Based on this, we constructed a gene co-expression network, identified the core genes and interacted gene pairs from the conservative modules. Finally, we checked the distribution of Nucleotide-binding and leucine-rich repeat (NLR) genes in the co-expression network and drew the wheat NLR gene co-expression network. In order to provide accessible information for related researchers, we built a web-based visualization platform to display the data. Based on the analysis, we found that resistance-related genes such as TaPR1, TaWRKY18 and HSP70 were highly expressed in the network. They were likely to be involved in the biological processes of Pst infecting wheat. This study can assist scholars in conducting studies on the pathogenesis and help to advance the investigation of wheat-Pst interaction patterns.

Molecular characterization of stable QTL and putative candidate genes for grain zinc and iron concentrations in two related wheat populations.

KEY MESSAGE: Major QTL for grain zinc and iron concentrations were identified on the long arm of chromosomes 2D and 6D. Gene-based KASP markers were developed for putative candidate genes TaIPK1-2D and TaNAS10-6D. Micronutrient malnutrition is one of the most common public health problems in the world. Biofortification, the most attractive and sustainable solution to surmount malnutrition requires the development of micronutrient enriched new crop cultivars. In this study, two recombinant inbred line (RIL) populations, ZM175/XY60 and ZM175/LX987, were used to identify QTL for grain zinc concentration (GZnC), grain iron concentration (GFeC) and thousand grain weight (TGW). Eight QTL for GZnC, six QTL for GFeC and five QTL for TGW were detected. Three QTL on chromosomes 2DL and 4BS and chromosome 6A showed pleiotropic effects on all three traits. The 4BS and 6A QTL also increased plant height and might be Rht-B1a and Rht25a, respectively. The 2DL locus within a suppressed recombination region was identified in both RIL populations and the favorable allele simultaneously increasing GZnC, GFeC and TGW was contributed by XY60 and LX987. A QTL on chromosome 6DL associated only with GZnC was detected in ZM175/XY60 and was validated in JD8/AK58 RILs using kompetitive allele-specific PCR (KASP) marker K_AX-110119937. Both the 2DL and 6DL QTL were new loci for GZnC. Based on gene annotations, sequence variations and expression profiles, the phytic acid biosynthesis gene TaIPK1-2D and nicotianamine synthase gene TaNAS10-6D were predicted as candidate genes. Their gene-based KASP markers were developed and validated in a cultivar panel of 343 wheat accessions. This study investigated the genetic basis of GZnC and GFeC and provided valuable candidate genes and markers for breeding Zn- and Fe-enriched wheat.

What is the spatiotemporal relationship between urbanization and ecosystem services? A case from 110 cities in the Yangtze River Economic Belt, China.

Rapid urbanization has altered landscape patterns and ecological functions, causing a decline in ecosystem service and generating many ecological and environmental issues. Studying the spatiotemporal interaction between urbanization and ecosystem service (ES) can provide effective supports for regional sustainability and policy formulation. This research utilizes the Yangtze River Economic Belt (YREB) as a case to analyze the spatiotemporal interaction between multi-urbanization indicators and multi-ESs over a large-scale region. The results show that the urbanization process in the YREB evolves from a rapidly growing state to a steady state with a slower rise. The urbanization level of the Yangtze River Delta urban agglomeration is relatively higher than the other regions. The distribution pattern of urbanization shows an overall characteristic of lower urbanization in the west and higher in the east. From 2009 to 2016, ecosystem service value (ESV) in the YREB decreased first and then increased, ESV in 2016 showed a reduction of 12.768 billion yuan compared with the 2009 level. ESV increases gradually from highly urbanized areas to those with lower levels of urbanization. Areas with high ESV levels are distributed at the middle reaches of YREB. There is a U-shaped curve relationship between urbanization and ESV, the ESV sharply increased when the urbanization index exceeded 0.6 in 2012. Land urbanization has the greatest impact on ESV among the four subtypes of urbanization indicators. Urbanization and ESV show the synergy relationship mostly in the eastern region, accounting for 18.18% of the total 110 cities. By contrast, they present the trade-off relationship in northern, southern and central regions, occupying 47.27% of the total observations. This study is helpful to provide scientific suggestions regarding the development of new urbanization, the protection of ESV, and the issue of how to achieve synergistic and sustainable development between them.

Mapping QTL for seedling morphological and physiological traits under normal and salt treatments in a RIL wheat population.

KEY MESSAGE: The genetic basis of 27 seedling traits under normal and salt treatments was fully analyzed in a RIL wheat population, and seven QTL intervals were validated in two other genetic populations. Soil salinity seriously constrains wheat (Triticum aestivum L.) production globally by influencing its growth and development. To explore the genetic basis of salt tolerance in wheat, a recombinant inbred line (RIL) population derived from a cross between high-yield wheat cultivar Zhongmai 175 (ZM175) and salt-tolerant cultivar Xiaoyan 60 (XY60) was used to map QTL for seedling traits under normal and salt treatments based on a high-density genetic linkage map. A total of 158 stable additive QTL for 27 morphological and physiological traits were identified and distributed on all wheat chromosomes except 3A and 4D. They explained 2.35-46.43% of the phenotypic variation with a LOD score range of 2.61-40.38. The alleles from XY60 increased corresponding traits for 100 QTL, while the alleles from ZM175 had positive effects for the other 58 QTL. Nearly half of the QTL (78/158) were mapped in nine QTL clusters on chromosomes 2A, 2B, 2D, 4B, 5A, 5B, 5D, and 7D (2), respectively. To prove the reliability and potentiality in molecular marker-assisted selection (MAS), seven QTL intervals were validated in two other genetic populations. Besides additive QTL, 94 pairs of loci were detected with significant epistatic effect and 20 QTL were found to interact with treatment. This study provides a full elucidation of the genetic basis of seedling traits (especially root system-related traits) associated with salt tolerance in wheat, and the developed kompetitive allele-specific PCR markers closely linked to stable QTL would supply strong supports to MAS in salt-tolerant wheat breeding.

Chromosomal composition analysis and molecular marker development for the novel Ug99-resistant wheat-Thinopyrum ponticum translocation line WTT34.

KEY MESSAGE: A novel Ug99-resistant wheat-Thinopyrum ponticum translocation line was produced, its chromosomal composition was analyzed and specific markers were developed. Stem rust caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn (Pgt) has seriously threatened global wheat production since Ug99 race TTKSK was first detected in Uganda in 1998. Thinopyrum ponticum is near immune to Ug99 races and may be useful for enhancing wheat disease resistance. Therefore, developing new wheat-Th. ponticum translocation lines that are resistant to Ug99 is crucial. In this study, a novel wheat-Th. ponticum translocation line, WTT34, was produced. Seedling and field evaluation revealed that WTT34 is resistant to Ug99 race PTKST. The resistance was derived from the alien parent Th. ponticum. Screening WTT34 with markers linked to Sr24, Sr25, Sr26, Sr43, and SrB resulted in the amplification of different DNA fragments from Th. ponticum, implying WTT34 carries at least one novel stem rust resistance gene. Genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization (mc-FISH), and multi-color GISH (mc-GISH) analyses indicated that WTT34 carries a T5DS·5DL-Th translocation, which was consistent with wheat660K single-nucleotide polymorphism (SNP) array results. The SNP array also uncovered a deletion event in the terminal region of chromosome 1D. Additionally, the homeology between alien segments and the wheat chromosomes 2A and 5D was confirmed. Furthermore, 51 PCR-based markers derived from the alien segments of WTT34 were developed based on specific-locus amplified fragment sequencing (SLAF-seq). These markers may enable wheat breeders to rapidly trace Th. ponticum chromosomal segments carrying Ug99 resistance gene(s).

Genome-wide association study of yield and related traits in common wheat under salt-stress conditions.

BACKGROUND: Soil salinization is a major threat to wheat production. It is essential to understand the genetic basis of salt tolerance for breeding and selecting new salt-tolerant cultivars that have the potential to increase wheat yield. RESULT: In this study, a panel of 191 wheat accessions was subjected to genome wide association study (GWAS) to identify SNP markers linked with adult-stage characters. The population was genotyped by Wheat660K SNP array and eight phenotype traits were investigated under low and high salinity environments for three consecutive years. A total of 389 SNPs representing 11 QTLs were significantly associated with plant height, spike number, spike length, grain number, thousand kernels weight, yield and biological mass under different salt treatments, with the phenotypic explanation rate (R2) ranging from 9.14 to 50.45%. Of these, repetitive and pleiotropic loci on chromosomes 4A, 5A, 5B and 7A were significantly linked to yield and yield related traits such as thousand kernels weight, spike number, spike length, grain number and so on under low salinity conditions. Spike length-related loci were mainly located on chromosomes 1B, 3B, 5B and 7A under different salt treatments. Two loci on chromosome 4D and 5A were related with plant height in low and high salinity environment, respectively. Three salt-tolerant related loci were confirmed to be important in two bi-parental populations. Distribution of favorable haplotypes indicated that superior haplotypes of pleiotropic loci on group-5 chromosomes were strongly selected and had potential for increasing wheat salt tolerance. A total of 14 KASP markers were developed for nine loci associating with yield and related traits to improve the selection efficiency of wheat salt-tolerance breeding. CONCLUSION: Utilizing a Wheat660K SNPs chip, QTLs for yield and its related traits were detected under salt treatment in a natural wheat population. Important salt-tolerant related loci were validated in RIL and DH populations. This study provided reliable molecular markers that could be crucial for marker-assisted selection in wheat salt tolerance breeding programs.

Cytogenetic identification and molecular marker development for the novel stripe rust-resistant wheat-Thinopyrum intermedium translocation line WTT11.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. Xiaoyan 78829, a partial amphidiploid developed by crossing common wheat with Thinopyrum intermedium, is immune to wheat stripe rust. To transfer the resistance gene of this excellent germplasm resource to wheat, the translocation line WTT11 was produced by pollen irradiation and assessed for immunity to stripe rust races CYR32, CYR33 and CYR34. A novel stripe rust-resistance locus derived from Th. intermedium was confirmed by linkage and diagnostic marker analyses. Molecular cytogenetic analyses revealed that WTT11 carries a TTh·2DL translocation. The breakpoint of 1B was located at 95.5 MB, and the alien segments were found to be homoeologous to wheat-group chromosomes 6 and 7 according to a wheat660K single-nucleotide polymorphism (SNP) array analysis. Ten previously developed PCR-based markers were confirmed to rapidly trace the alien segments of WTT11, and 20 kompetitive allele-specific PCR (KASP) markers were developed to enable genotyping of Th. intermedium and common wheat. Evaluation of agronomic traits in two consecutive crop seasons uncovered some favorable agronomic traits in WTT11, such as lower plant height and longer main panicles, that may be applicable to wheat improvement. As a novel genetic resource, the new resistance locus may be useful for wheat disease-resistance breeding. Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-021-00060-3.

Mapping QTL for agronomic traits under two levels of salt stress in a new constructed RIL wheat population.

KEY MESSAGE: QTL for 15 agronomic traits under two levels of salt stress in dry salinity field were mapped in a new constructed RIL population utilizing a Wheat55K SNP array. Furthermore, eight QTL were validated in a collected natural population. Soil salinity is one of the major abiotic stresses causing serious impact on crop growth, development and yield. As one of the three most important crops in the world, bread wheat (Triticum aestivum L.) is severely affected by salinity, too. In this study, an F7 recombinant inbred line (RIL) population derived from a cross between high-yield wheat cultivar Zhongmai 175 and salt-tolerant cultivar Xiaoyan 60 was constructed. The adult stage performances of the RIL population and their parent lines under low and high levels of salt stress were evaluated for three consecutive growing seasons. Utilizing a Wheat55K SNP array, a high-density genetic linkage map spinning 3250.71 cM was constructed. QTL mapping showed that 90 stable QTL for 15 traits were detected, and they were distributed on all wheat chromosomes except 4D, 6B and 7D. These QTL individually explained 2.34-32.43% of the phenotypic variation with LOD values ranging from 2.68 to 47.15. It was found that four QTL clusters were located on chromosomes 2D, 3D, 4B and 6A, respectively. Notably, eight QTL from the QTL clusters were validated in a collected natural population. Among them, QPh-4B was deduced to be an allele of Rht-B1. In addition, three kompetitive allele-specific PCR (KASP) markers derived from SNPs were successfully designed for three QTL clusters. This study provides an important base for salt-tolerant QTL (gene) cloning in wheat, and the markers, especially the KASP markers, will be useful for marker-assisted selection in salt-tolerant wheat breeding.

Identification of an Elite Wheat-Rye T1RS·1BL Translocation Line Conferring High Resistance to Powdery Mildew and Stripe Rust.

Wheat-rye T1RS·1BL translocations have been widely used worldwide in wheat production for multiple disease resistance and superior yield traits. However, many T1RS·1BL translocations have successively lost their resistance to pathogens due to the coevolution of pathogen virulence with host resistance. Because of the extensive variation in rye (Secale cereale L.) as a naturally cross-pollinating relative of wheat, it still has promise to widen the variation of 1RS and to fully realize its application value in wheat improvement. In the present study, the wheat-rye breeding line R2207 was characterized by comprehensive analyses using genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization with multiple probes, multicolor GISH, and molecular marker analysis, and then was proven to be a cytogenetically stable wheat-rye T1RS·1BL translocation line. Based on the disease responses to different isolates of powdery mildew and genetic analysis, R2207 appears to possess a novel variation for resistance, which was confirmed to be located on the rye chromosome arm 1RS. Line R2207 also exhibited high levels of resistance to stripe rust at both seedling and adult stages, as well as enhanced agronomic performance, so it has been transferred into a large number of commercial cultivars using an efficient 1RS-specific kompetitive allele specific PCR marker for marker-assisted selection.

Spatial differences of ecosystem services and their driving factors: A comparation analysis among three urban agglomerations in China's Yangtze River Economic Belt.

Understanding the spatial distribution characteristics of ecosystem service value (ESV) and their underlying driving factors is critical for ecosystem service management. Using three national-level urban agglomerations in the Yangtze River Economic Belt, Cheng-Yu (CY), Middle-Reach Yangtze River (MRYR), and Yangtze River Delta (YRD), as a case study, this paper quantifies the ESVs and the spatial distribution characteristics, analyzes the driving factors of ESVs using the stochastic impacts by regression on population, affluence, and technology model (STIRPAT). The results specify that: (1) Over the study period 2009-2016, the total ESV of the three urban agglomerations decreases by 5498.70 million USD. The regulating, supporting, and cultural service decrease by 4607.60, 2648.01, and 1182.25 million USD, respectively, while the provisioning service increases by 2795.15 million USD. (2) ESV in MRYR undergoes the largest reduction of 4269.70 million USD, followed by CY and YRD with 1015.66 and 213.35 million USD from 2009 to 2016. (3) In 2016, among the 70 cities at the prefecture level or above, the cities with high total ESV, per unit area ESV, and per capita EVS are mainly distributed to the areas of the south Yangtze River of MRYR and YRD, MRYR, and MRYR and YRD, respectively. (4) In general, land use and cover, population are the main factors affecting ESVs, followed by economic, social and political factors. Among the three urban agglomerations, population, land use and cover basically have the equally important impacts on ESV in CY; land use and cover, especially the proportion of urban construction land has the greatest impact on ESV in MRYR; population, especially the urbanization rate has the greatest impact in YRD. The comparative analysis of the driving factors of ESVs in different regions is helpful to propose differentiated ecological protection policies and promote the increase of ESV accordingly.

Development of Novel Wheat-Rye Chromosome 4R Translocations and Assignment of Their Powdery Mildew Resistance.

Rye (Secale cereale L.) is an important gene donor for wheat improvement because of its many valuable traits, especially disease resistance. Development of novel wheat-rye translocations with disease resistance can contribute to transferring resistance into common wheat. In a previous study, a wheat-rye T4BL·4RL and T7AS·4RS translocation line (WR41-1) was developed by distant hybridization, and it was speculated that its resistance to powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), was derived from rye based on pedigree analysis. To make accurate use of chromosome 4R in wheat improvement, a set of new 4R translocations involving different arm translocations (e.g., 4RS monosomic, 4RL monosomic, 4RL disomic, 4RS monosomic plus 4RL monosomic, 4RS monosomic plus 4RL disomic, and 4RS disomic plus 4RL disomic translocations) was developed from crosses with common wheat. Those translocations were characterized by genomic in situ hybridization and expressed sequence tag simple sequence repeat marker analysis. To confirm the source of powdery mildew resistance, the translocation plants were tested against Bgt isolate E09. The results indicated that all translocations with 4RL were resistant at all tested growth stages, whereas those with only 4RS translocation or no alien translocation were susceptible. This further indicated that the powdery mildew resistance of WR41-1 was derived from the alien chromosome arm 4RL. To effectively use 4RL resistance in wheat improvement, two competitive allele-specific PCR markers specific for chromosome arm 4RL were developed to detect the alien chromosome in the wheat genome. These new translocation lines with diagnostic markers can efficiently serve as important bridges for wheat improvement.

Does China's Yangtze River Economic Belt policy impact on local ecosystem services?

The ecological protection of the Yangtze River Economic Belt (YREB) is one part of China's national strategy, and to identify the spatiotemporal variation of ecosystem service values (ESV) and examine the YREB policies performances can provide effective knowledge and supports for making ecological protection policies. In this paper, the ESV of YREB's 11 units were measured based on equivalent factor value method. Panal data and regression discontinuity model were used to discuss the impact of the ecological protection policies issued 2012 and 2014 on the ESVs. The results showed that: (1) From 2009 to 2016, the total ESVs of the YREB increased from 617.49 billion USD to 844.84 billion USD, showing a pattern of slow increase (2009-2012), substantial growth (2012-2014) and stability of high level (2014-2016). Forestland and water body were the key types of land to ecological protection. For the average of all measured years, the two lands accounted for 43.24% of total ecological land and provided 82.36% of total ESVs;(2) Generally, all the units were closely related to the ecological protection policy and were positively affected. In the first period (2009-2012), the ESVs of 11 units had three statuses: declined, kept steady and moderately increased. After strong policy implementation, all units rose sharply (2012-2014) and maintained a steady increase at a high level (2014-2016); (3) Ecological protection policies have a significant positive effect on the ESVs. The policy in 2012 suppressed the downward trend of ESVs increase and the policy in 2014 had a positive impact to increase ESVs. This study proved that possible to achieve a win-win situation of urban development and ecological environmental protection by implementing ecological protection policies.

Development and molecular cytogenetic identification of a new wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust and sharp eyespot.

KEY MESSAGE: A wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust, sharp eyespot and high kernel number per spike was developed and characterized by molecular cytogenetic method as novel resistant germplasm. Rye (Secale cereale L.), a close relative of common wheat, is an important and valuable gene donor with multiple disease resistance for wheat improvement. However, resistance genes derived from rye have successively lost resistance to pathogens due to the coevolution of pathogen virulence and host resistance. Development and identification of new effective resistance gene sources from rye therefore are of special importance and urgency. In the present study, a wheat-rye line WR35 was produced through distant hybridization, embryo rescue culture, chromosome doubling and backcrossing. WR35 was then proven to be a new wheat-rye 4R disomic addition line using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization) and ND-FISH (non-denaturing FISH) with multiple probes, mc-GISH (multicolor GISH), rye chromosome arm-specific marker analysis and SLAF-seq (specific-locus amplified fragment sequencing) analysis. At the adult stage, WR35 exhibited high levels of resistance to the powdery mildew (Blumeria graminis f. sp. tritici, Bgt) and stripe rust (Puccinia striiformis f. sp. tritici, Pst) pathogens prevalent in China, and a highly virulent isolate of Rhizoctonia cerealis, the cause of wheat sharp eyespot. At the seedling stage, it was highly resistant to 22 of 23 Bgt isolates and four Pst races. Based on its disease responses to different pathogen isolates, WR35 may possess resistance gene(s) for powdery mildew, stripe rust and sharp eyespot, which differed from the known resistance genes from rye. In addition, WR35 was cytologically stable and produced high kernel number per spike. Therefore, WR35 with multi-disease resistances and desirable agronomic traits should serve as a promising bridging parent for wheat chromosome engineering breeding.

Physical mapping of the blue-grained gene from Thinopyrum ponticum chromosome 4Ag and development of blue-grain-related molecular markers and a FISH probe based on SLAF-seq technology.

KEY MESSAGE: A Thinopyrum ponticum chromosome 4Ag physical map was constructed, the blue-grained gene was localized, and related specific markers and a FISH probe were developed by SLAF-seq. Decaploid Thinopyrum ponticum (2n = 10x = 70) serves as an important gene pool for wheat improvement. The wheat-Th. ponticum 4Ag (4D) disomic substitution line Blue 58, derived from a distant hybridization between Th. ponticum and common wheat (Triticum aestivum L.), bears blue coloration in the aleurone layer. To map the blue-grained gene, eight wheat-Th. ponticum 4Ag translocation lines with different chromosomal segment sizes were obtained from Blue 58 using 60Co-γ ray irradiation and were characterized using cytogenetic and molecular marker analysis. A small-segment blue-grained wheat translocation line L13, accounting for one-fifth of 4AgL, was obtained. A physical map of chromosome 4Ag was constructed containing 573 specific-locus amplified fragment sequencing (SLAF-seq) markers, including three bins with 223 markers on 4AgS and eight bins with 350 markers on 4AgL. The blue-grained gene in three blue-grained translocation lines L5, L9, and L13, was located on bin 4AgL-6 with FL 0.75-0.89. Moreover, 89 blue-grain-related molecular markers and one fluorescence in situ hybridization (FISH) probe, pThp12.19, were identified in this bin. The newly developed translocation lines and the molecular markers and FISH probe will facilitate the application of the Th. ponticum-origin blue-grained characteristic in wheat breeding.

Development of Thinopyrum ponticum-specific molecular markers and FISH probes based on SLAF-seq technology.

MAIN CONCLUSION: Based on SLAF-seq, 67 Thinopyrum ponticum-specific markers and eight Th. ponticum-specific FISH probes were developed, and these markers and probes could be used for detection of alien chromatin in a wheat background. Decaploid Thinopyrum ponticum (2n = 10x = 70) is a valuable gene reservoir for wheat improvement. Identification of Th. ponticum introgression would facilitate its transfer into diverse wheat genetic backgrounds and its practical utilization in wheat improvement. Based on specific-locus-amplified fragment sequencing (SLAF-seq) technology, 67 new Th. ponticum-specific molecular markers and eight Th. ponticum-specific fluorescence in situ hybridization (FISH) probes have been developed from a tiny wheat-Th. ponticum translocation line. These newly developed molecular markers allowed the detection of Th. ponticum DNA in a variety of materials specifically and steadily at high throughput. According to the hybridization signal pattern, the eight Th. ponticum-specific probes could be divided into two groups. The first group including five dispersed repetitive sequence probes could identify Th. ponticum chromatin more sensitively and accurately than genomic in situ hybridization (GISH). Whereas the second group having three tandem repetitive sequence probes enabled the discrimination of Th. ponticum chromosomes together with another clone pAs1 in wheat-Th. ponticum partial amphiploid Xiaoyan 68.

Characterization of a Segregation Distortion Locus with Powdery Mildew Resistance in a Wheat-Thinopyrum intermedium Introgression Line WE99.

Exploitation of host resistance is important for controlling powdery mildew of wheat (Triticum aestivum L.). In this study, a wheat-Thinopyrum intermedium introgression line, designated WE99, conferred seedling resistance to 47 of 49 Blumeria graminis f. sp. tritici isolates. Genetic analysis demonstrated that the resistance segregation deviated significantly from a single gene Mendelian ratio. However, marker analysis indicated that only a single recessive resistance gene, temporarily designated PmWE99, conferred powdery mildew resistance (Pm). PmWE99 was mapped to chromosome arm 2BS and linked to the three simple-sequence repeat markers Gwm148, Gwm271, and Barc55. Using race spectrum analysis, PmWE99 was shown to be significantly different from the documented genes Pm42 and MlIW170 located on chromosome arm 2BS and, thus, appeared to be a new Pm gene. Examination of the genotype frequencies in the F2:3 families showed that a genetic variation in the PmWE99 interval that favored the transmission of the WE99 allele could be the cause of the deviated segregation. Further investigation revealed that the abnormal segregation only occurred at the PmWE99 interval and was not common at other loci in this population. Identification of PmWE99 will increase the diversity of the Pm genes for wheat improvement.

A modified nebulization modality versus classical ultrasonic nebulization and oxygen-driven nebulization in facilitating airway clearance in patients with acute exacerbation of chronic obstructive pulmonary disease: a randomized controlled trial.

BACKGROUND: Ultrasonic nebulization (UN) and oxygen-driven nebulization (ON), two commonly used modalities for nebulization inhalation, are not ideally suitable for patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). METHODS: A total of 91 patients with AECOPD were randomized to three groups given different nebulization modalities: ON, UN, and ultrasonic nebulization with warming and oxygen (UNWO). The sputum clearance, lung function, changes in physiological measures such as peripheral oxygen saturation (SpO2) and tolerance to these nebulization modalities were recorded and compared among the three groups. RESULTS: The time to the first expectoration was shorter and the sputum volume was larger after UN and UNWO than after ON (both P<0.01). Compared with pre-nebulization, SpO2 significantly increased (P<0.01) and the dyspnea decreased significantly (P<0.05) after UNWO. The SpO2 and dyspnea post-UNWO were significantly better than those post-UN (P<0.01, P<0.05), but not statistically different from those post-ON (both P>0.05). UNWO demonstrated significantly greater comfort and longer duration of nebulization than UN (P<0.01, P<0.05), but no significant differences in these respects from ON (both P>0.05). Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow (PEF) decreased significantly after UNWO (P<0.05, P<0.01, and P<0.01, respectively). CONCLUSIONS: UNWO may promote expectoration of sputum with fewer adverse reactions and a higher level of comfort than simple UN and ON. Therefore, it can be used as an adjuvant therapy for AECOPD patients.

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Chromosome Disomic Addition Line with Powdery Mildew Resistance.

Rye (Secale cereale L.) possesses many valuable genes that can be used for improving disease resistance, yield and environment adaptation of wheat (Triticum aestivum L.). However, the documented resistance stocks derived from rye is faced severe challenge due to the variation of virulent isolates in the pathogen populations. Therefore, it is necessary to develop desirable germplasm and search for novel resistance gene sources against constantly accumulated variation of the virulent isolates. In the present study, a new wheat-rye line designated as WR49-1 was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. Using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), mc-GISH (multicolor GISH) and EST (expressed sequence tag)-based marker analysis, WR49-1 was proved to be a new wheat-rye 6R disomic addition line. As expected, WR49-1 showed high levels of resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 19 of 23 Bgt isolates tested at the seedling stage. According to its reaction pattern to different Bgt isolates, WR49-1 may possess new resistance gene(s) for powdery mildew, which differed from the documented powdery mildew gene, including Pm20 on chromosome arm 6RL of rye. Additionally, WR49-1 was cytologically stable, had improved agronomic characteristics and therefore could serve as an important bridge for wheat breeding and chromosome engineering.

Molecular mapping of a new powdery mildew resistance gene Pm2b in Chinese breeding line KM2939.

KEY MESSAGE: An allele of Pm2 for wheat powdery mildew resistance was identified in a putative Agropyron cristatum -derived line and used in wheat breeding programs. Powdery mildew (caused by Blumeria graminis f. sp. tritici, Bgt) is one of the most devastating wheat diseases worldwide. It is important to exploit varied sources of resistance from common wheat and its relatives in resistance breeding. KM2939, a Chinese breeding line, exhibits high resistance to powdery mildew at both the seedling and adult stages. It carries a single dominant powdery mildew resistance (Pm) allele of Pm2, designated Pm2b, the previous allelic designation Pm2 will be re-designated as Pm2a. Pm2b was mapped to chromosome arm 5DS and flanked by sequence characterized amplified region (SCAR) markers SCAR112 and SCAR203 with genetic distances of 0.5 and 1.3 cM, respectively. Sequence tagged site (STS) marker Mag6176 and simple sequence repeat (SSR) marker Cfd81 co-segregated with SCAR203. Pm2b differs in specificity from donors of Pm2a, Pm46 and PmLX66 on chromosome arm 5DS. Allelism tests indicated that Pm2b, Pm2a and PmLX66 are allelic. Therefore, Pm2b appears to be a new allele at the Pm2 locus. The closely linked markers were used to accelerate transfer of Pm2b to wheat cultivars in current production.