Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust,caused by Puccinia triticina(Pt),is an important foliar disease that has an important influence on wheat yield.The most economic,safe and effective way to control the disease is growing resistant cultivars.In the present study,a total of 46 wheat landraces and 34 wheat lines with known Lr(leaf rust resistance)genes were inoculated with 16Pt pathotypes for postulating seedling resistance gene(s)in the greenhouse.These cultivars and five wheat differential lines with adult plant resistance(APR)genes(Lr12,Lr22b,Lr34,Lr35 and Lr37)were also evaluated for identification of slow rusting resistance in the field trials in Baoding,Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.Furthermore,10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.Nonetheless,Lr1 was detected only in Hongtangliangmai.The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.Lr genes namely,Lr9,Lr19,Lr24,Lr28,Lr29,Lr47,Lr51 and Lr53 were effective at the whole plant stage.Lr18,Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage.Lr34 as a slowing rusting gene showed good resistance in the field.Four race-specific APR genes Lr12,Lr13,Lr35 and Lr37 conferred good resistance in the field experiments.Seven race-specific genes,Lr2b,Lr2c,Lr11,Lr16,Lr26,Lr33 and LrB had lost resistance.The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.     

Genetic diversity of Russian common wheat varieties for leaf rust resistance

The results of evaluating resistance to leaf rust pathogen in Russian common wheat varieties recommended for growing in the Russian Federation are given. Their diversity with respect to Lr genes is assessed with the use of phytopathological and molecular methods and representativeness in growing regions is analyzed. A low genetic diversity among resistant varieties with domination of genes Lr9 and Lr19 and their confinement to Volga, Ural, and West Siberian regions are revealed.     

Identification and Genetic Analysis of a Novel Rice Spotted-Leaf Mutant with Broad-Spectrum Resistance to Xanthomonas oryzae pv. oryzae

A spotted-leaf mutant of rice HM143 was isolated from an EMS-induced IR64 mutant bank. Brown lesions randomly distributed on leaf blades were observed about 3 wk after sowing. The symptom lasted for the whole plant growth duration. Histochemical analysis indicated that cell death occurred in and around the site of necrotic lesions accompanied with accumulation of hydrogen hyperoxide. Agronomic traits were largely similar to the wild type IR64 except seed setting rate and 1 000-grain weight which were significantly decreased in the mutant. Disease resistance of the mutant to multiple races of Xanthomonas oryzae pv. oryzae was significantly enhanced. Genetic analysis showed that the mutation was controlled by a single recessive gene, tentatively termed splHM143. In addition, using molecular markers and 1023 mutant type individuals from an F2 segregating population derived from the cross HM143/R9308, the spotted-leaf gene was finally delimited to an interval of 149 kb between markers XX25 and ID40 on the long arm of chromosome 4. splHM143 is likely a novel rice spotted-leaf gene since no other similar genes have been identified near the chromosomal region.     

Characterization and fine mapping of a semi-rolled leaf mutant srl3 in rice

Moderate leaf rolling can maintain leaf erectness, improve light transmittance in the population, and improve light energy utilization, thereby increasing rice yield. This study used ethyl methanesulfonate (EMS) to treat Yunjing 17 (YJ17) and obtained a semi-rolled leaf mutant that was named semi-rolledleaf3 (srl3). We found that the rolled-leaf phenotype was due to the aberrant development of bulliform cells and the loss of sclerenchymatous cells. In addition, the shoot and root length of srl3 seedlings differed from the wild type. The srl3 mutant had significantly lower plant height and seed-setting rate but notably greater tiller number, panicle length, and primary branch number per panicle than the wild type. Genetic analysis showed that a single recessive nuclear gene defined the srl3 mutant, and it was precisely located in a 144-kb region between two insertion-deletion (InDel) markers, M8 and M19, on chromosome 2. In this region, no leaf-rolling-related genes have been reported previously. Thus, the study indicated that SRL3 is a novel leaf-rolling-related gene, and the results laid the foundation for the cloning and functional analysis of the SRL3 gene.     

十个粳稻品种对稻瘟病抗性和抗性遗传分析

 10个粳稻品种,在3～4叶期和抽德初期于温室内,用7个稻瘟病菌生理小种即ZA₁,ZB₁₃,ZC₁₃,ZD₁,ZE₁,ZF₁和ZG₁进行人工接种,结果表明:苗叶瘟和穗瘟的抗性85.70%反应一致,呈正相关。10个品种与广谱感病品种丽江新团黑谷的杂交组合,根据F₁,F₂,B₁F₁分析结果:F₁95%抗性呈显性、不完全显性和隐性各占2%;该10个品种对多个测试小种的抗性,多受两对或1对显性基因控制,少数受1对隐性基因或3对显性基因控制。基因分析表明:这10个抗源品种至少各含有两对不尽相同的抗瘟性基因,在抗瘟性遗传上属不同抗源。根据6个杂交组合的正、反交分析结果,稻瘟病抗性属细胞核遗传,但也有的受细胞质作用影响。     

Identification of a Resistance Gene bls1 to Bacterial Leaf Streak in Wild Rice Oryza rufipogon Griff.

Bacterial leaf streak (BLS) of rice, caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a worldwide destructive disease. Development of resistant varieties is considered to be one of the most effective and eco-friendly ways to control the disease. However, only a few genes/QTLs having resistance to BLS have been identified in rice until now. In the present study, we have identified and primarily mapped a BLS-resistance gene, bls1, from a rice line DP3, derived from the wild rice species Oryza rufipogon Griff. A BC₂F₂ (9311/DP3//9311) population was constructed to map BLS-resistance gene in the rice line DP3. The segregation of the resistant and susceptible plants in BC₂F₂ in 1:3 ratio (χ²=0.009, χ²_{0.05, 1}=3.84, P>0.05), suggested that a recessive gene confers BLS resistance in DP3. In bulked segregant analysis (BSA), two SSR markers RM8116 and RM584 were identified to be polymorphic in resistant and susceptible DNA bulks. For further mapping the resistance gene, six polymorphic markers around the target region were applied to analyze the genotypes of the BC₂F₂ individuals. As a result, the BLS-resistant gene, designated as bls1, was mapped in a 4.0-cM region flanked by RM587 and RM510 on chromosome 6.     

How Specific is Non-Hypersensitive Host and Nonhost Resistance of Barley to Rust and Mildew Fungi？

Full nonhost resistance can be defined as immunity, displayed by an entire plant species against all genotypes of a plant pathogen. Interesting biological questions are, whether the genes responsible for the nonhost status of a plant species have a general or a specific effectiveness to heterologous （＂nonhost＂） pathogens？ Is the nonhost resistance to pathogens of plant species that are related to the nonhost based on R-genes or on other types of genes？ We study this question in barley （Hordeum vulgare L.）, which is a near-nonhost to several rusts （Puccinia） of cereals and grasses. By crosses and selection we accumulated susceptibility and developed an experimental line, SusPtrit, with high susceptibility to at least nine different heterologous rust taxa such as the wheat and Agropyron leaf rusts （P. triticina and P. persistens, respectively）. At the microscopic level there is also some variation among barley accessions in the degree that the heterologous wheat powdery mildew （Blumeria graminis f.sp. tritici） is able to form haustoria in epidermal cells. So, also the genetics of the variation in level of nonhost resistance to heterologous mildew fungi can be studied in barley. Our data obtained on mapping populations involving three regular nonhost-immune accessions （Vada, Cebada Capa and Golden Promise） suggest that nonhost resistance is the joined effect of multiple, quantitative genes （QTLs） and very occasionally a major gene （R-gene？） is involved. Most QTLs have effect to only one or two heterologous rusts, but some have a wider spectrum. This was confirmed in a set of QTL-NILs. Those QTL-NILs are used to fine-map the effective genes. In some cases, a QTL region with effectiveness to several heterologous rusts might be a cluster of genes with a more narrow spectrum of effectiveness. Our evidence suggests that nonhost resistance in barley to rust and powdery mildew fungi of related Gramineae is not due to R-genes, but to pathogen species-specific quantitative resistance genes.     

日光温室秋冬番茄多抗优良品种的筛选

本试验主要对14个番茄材料进行了Ty-1,Ty-2,Ty-3,Mi-1和Cf-9共5个抗性基因的检测,并在自然条件下观察番茄植株对黄化曲叶病毒病、叶霉病、根结线虫病的抗性.生物学检测结果表明, 14个材料均含有黄化曲叶病毒病抗性基因、根结线虫抗性基因Mi-1和番茄叶霉病抗性基因Cf-9.其中, 2个番茄材料含有5个抗性基因, 8个材料含有4个抗性基因, 4个材料含有3个抗性基因.田间抗病性调查并未发现显著的感病情况.此外,还对其生长习性等13个农艺性状进行了调查和统计.综合抗病能力以及田间表现, 14,21,金棚8B等3个品种抗病能力强,生长势好,产量较高,比较适宜日光温室秋冬茬番茄的种植.     

Systemic acquired resistance,NPR1, and pathogenesis-related genes in wheat and barley

In Arabidopsis, systemic acquired resistance (SAR) is established beyond the initial infection by a pathogen or is directly induced by treatment with salicylic acid (SA) or its functional analogs, 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole (BTH). NPR1 protein is considered the master regulator of SAR in both SA signal sensing and transduction. In wheat (Triticum aestivum) and barley (Hordeum vulgare), both pathogen infection and BTH treatment can induce broad-spectrum resistance to various diseases, including powdery mildew, leaf rust, Fusarium head blight, etc. However, three different types of SAR-like responses including acquired resistance (AR), systemic immunity (SI), and BTH-induced resistance (BIR) seem to be achieved by activating different gene pathways. Recent research on wheat and barley NPR1 homologs in AR and SI has provided the initial clue for understanding the mechanism of SAR in these two plant species. In this review, the specific features of AR, SI, and BIR in wheat and barley were summarized and compared with that of SAR in model plants of Arabidopsis and rice. Research updates on downstream genes of SAR, including pathogenesis-related (PR) and BTH-induced genes, were highlighted.     

Development of Molecular Marker Linked to Cf-10 Gene Using SSR and AFLP Method in Tomato

The leaf mould resistance gene Cf-10 on tomato confered resistant or immune to all prevalent physiological races of Cladosporium fulvum presented in three northeastern provinces of China in inoculation...     

Evaluation and Genetic Analysis of Five Parental Varieties Resistant to Rice Blast Pathogen in Heilongjiang Province

Five F2 segregation populations, derived from crosses between the susceptible japonica cultivars （cvs.） Kongyul31 and donor cvs. Aichi Asahi （AA）, BL1, Digu, Pai-kan-tao （PKT） and Oryzica Llanos 5 （ORL...     

Pathogenesis-related protein genes involved in race-specific all-stage resistance and non-race specific high-temperature adult-plant resistance to Puccinia striiformis f. sp. tritici in wheat

Interactions of the stripe rust pathogen (Puccinia striiformis f. sp. tritici) with wheat plants activate a wide range of host responses. Among various genes involved in the plant-pathogen interactions, the expressions of particular pathogenesis-related (PR) protein genes determine different defense responses. Different types of resistance have been recognized and utilized for developing wheat cultivars for resistance to stripe rust. All-stage resistance can be detected in seedling stage and remains at high levels throughout the plant growth stages. This type of resistance is race-specific and not durable. In contrast, plants with only high-temperature adult-plant (HTAP) resistance are susceptible in seedling stage, but become resistant when plants grow older and the weather becomes warmer. HTAP resistance controlled by a single gene is partial, but usually non-race specific and durable. The objective of this study was to analyze the expression of PR protein genes involved in different types of wheat resistance to stripe rust. The expression levels of 8 PR protein genes (PR1, PR1.2, PR2, PR3, PR4, PR5, PR9 and PR10) were quantitatively evaluated at 0, 1, 2, 7 and 14 days after inoculation in single resistance gene lines of wheat with all-stage resistance genes YrTr1, Yr76, YrSP and YrExp2 and lines carrying HTAP resistance genes Yr52, Yr59, Yr62 and Yr7B. Races PSTv-4 and PSTv-37 for compatible and incompatible interactions were used in evaluation of PR protein gene expression in wheat lines carrying all-stage resistance genes in the seedling-stage experiment while PSTv-37 was used in the HTAP experiment. Analysis of quantitative real-time polymerase chain reaction (qRT-PCR) revealed that all of the PR protein genes were involved in the different types of resistance controlled by different Yr genes. However, these genes were upregulated at different time points and at different levels during the infection process among the wheat lines with different Yr genes for either all-stage resistance or HTAP resistance. Some of the genes were also induced in compatible interactions, but the levels were almost always higher in the incompatible interaction than in the compatible interaction at the same time point for each Yr gene. These results indicate that both allsalicylic acid and jasmonate signaling pathways are involved in both race-specific all-stage resistance and non-race specific HTAP resistance. Although expressing at different stages of infection and at different levels, these PR protein genes work in concert for contribution to different types of resistance controlled by different Yr genes.     

Donors of spring common wheat resistance to leaf rust and powdery mildew with genetic material of the species Aegilops speltoides L., Aegilops triuncialis L., and Triticum kiharae Dorof. et Migusch

Spring wheat donors obtained by the wide hybridization method with several leaf rust and powdery mildew resistance genes effective for the Non-Chernozem Zone of the Russian Federation have been identified. The presence of effective genes of resistance to leaf rust (Lr37, Lr39, Lr46, Lr50) and powdery mildew (Pm2, Pm13) that can be used in breeding for immunity with STS and SSR markers has been established.     

Identification of the resistance gene to powdery mildew in Chinese wheat landrace Baiyouyantiao

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most damaging diseases to wheat in the world. The cultivation of resistant varieties of wheat is essential for controlling the powdery mildew epidemic. Wheat landraces are important resources of resistance to many diseases. Mapping powdery mildew resistance genes from wheat landraces will promote the development of new varieties with disease resistance. The Chinese wheat landrace Baiyouyantiao possesses characteristic of disease resistance to powdery mildew. To identify the resistance gene in this landrace, Baiyouyantiao was crossed with the susceptible cultivar Jingshuang 16 and seedlings of parents and F₁, BC₁, F₂, and F_2:3 were tested with Bgt isolate E09. The genetic results showed that the resistance of Baiyouyantiao to E09 was controlled by a single recessive gene, tentatively designated PmBYYT. An Illumina wheat 90K single-nucleotide polymorphism (SNP) array was applied to screen polymorphisms between F₂-resistant and F₂-susceptible DNA bulks for identifying the chromosomal location of PmBYYT. A high percentage of polymorphic SNPs between the resistant and susceptible DNA bulks was found on chromosome 7B, indicating that PmBYYT may be located on this chromosome. A genetic linkage map of PmBYYT consisting of two simple sequence repeat markers and eight SNP markers was developed. The two flanking markers were SNP markers W7BL-8 and W7BL-15, with genetic distances of 3 and 2.9 cM, respectively. The results of this study demonstrated the rapid characterization of a wheat disease resistance gene and SNP marker development using the 90K SNP assay. The flanking markers of gene PmBYYT will benefit marker-assisted selection (MAS) and map-based cloning in breeding wheat cultivars with powdery mildew resistance.     

Monitoring the development of leaf rust pathogen on common wheat specimens

During 1995–2005 the leaf rust pathogen was monitored on common wheat specimens with identified Lr resistance genes. The number of pustules on the flag leaf surface of the host plant, pustule area, number of spores in it, and type of reaction are used as the main indices of pathogenesis of the pathogen. A number of regression models reflecting the main quantitative regularities of variables of the pathogen’s state are proposed.     

水稻香味与光滑叶和CMS基因的遗传关系研究

本项研究采用ＫＯＨ溶液浸提法鉴别水稻叶片的香味。试验表明：川香２８Ａ的叶片香味和雄性不育基因分别受２对隐性基因控制。原产美国的光滑稻品种Ｌｅｍｏｎｔ,ＳｈｏｒｔＭａｒｓ和ＢｌｕｅＢｅｌ的光滑叶性状均受一对隐性基因支配。香味基因与光滑叶基因,以及香味基因与ＣＭＳ基因均表现为独立遗传。     

Effects of gamma irradiation times on some flowering characteristics and pest resistances in two almond (Prunus amygdalus L.) cultivars

This study was conducted to evaluate the effects of different gamma-radiation exposition times on some biological traits of two late-blooming almond cultivars of ??A200?? and ??Sahand??. Current season shoots of ??A200?? and ??Sahand?? were exposed to 36 ??C gamma-radiation for 0, 5, 10, 30 and 150 minutes. The experiment was carried out on 4-years old trees based on completely randomized design. Analysis of variance showed that buds break date, bearing type, leaf area, resistance to aphid and mite as well as Polystigma were significantly influenced by different gamma irradiation times (p < 0.05). There were significant differences between two cultivars for bearing type, leaf area, and resistance to pests (p < 0.05). 30 minute gamma irradiation was increased buds break date and in this treatment, mutated trees had very late bud break date and they were late flowering habit. Gamma irradiation treatments were changed bearing type. The highest leaf area was achieved on 150 minute gamma irradiation. Short and long time treatments had not efficiency on improving resistance to Polystigma. The highest resistance to aphid and mite were observed on 150 minute gamma irradiation. Two studied cultivars were relatively resistance to aphid (control), but mutated trees had tended to resistance to aphid. Mutated trees had medium to relatively resistance to mite. Therefore, gamma irradiation treatments can be improved high considerable resistance to mite.     

NBS Profiling Identifies Potential Novel Locus from Solanum demissum That Confers Broad-Spectrum Resistance to Phytophthora infestans

Potato late blight, caused by the oomycete pathogen Phytophthora infestans, is the most serious disease of potato worldwide. The adoption of varieties with resistance genes, especially broad-spectrum resistance genes, is the most efficient approach to control late blight. Solanum demissum is a well-known wild potato species from which 11 race-specific resistance genes have been identified, however, no broad-spectrum resistance genes like RB have been reported in this species. Here, we report a novel reisistance locus from S. demissum that potentially confer broad-spectrum resistance to late blight. A small segregating population of S. demissum were assessed for resistance to aggressive P. infestans isolates（race 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11）. This coupled with nucleotide binding site（NBS） profiling analyses, led to the identification of three fragments that linked to the potential candidate resistance gene（s）. Cloning and sequence analysis of these fragments suggested that the identified resistance gene locus is located in the region containing R2 resistance gene at chromosome 4. Based on the sequences of the cloned fragments, a co-segregating sequence characterized amplified region（SCAR） marker, RDSP, was developed. The newly identified marker RDSP will be useful for marker assisted breeding and further cloning of this potential resistance gene locus.     

Screening of drought resistance indices and evaluation of drought resistance in cotton (Gossypium hirsutum L.)

Sixteen cotton cultivars widely planted in China were sowed under five different drought concentrations (0, 2.5, 5, 7.5, and 10%) using PEG₆₀₀₀ to screen the indices of drought resistance identification and explore the drought resistance of different cotton cultivars. Eighteen physiological indices including root, stem, and leaf water contents (RWC, SWC, and LWC), net photosynthetic rate (P_n), the maximum photochemical quantum yield (F_v/F_m), the actual photochemical quantum yield (ϕPSII), non-photochemical quenching coefficient (NPQ), leaf water potential (LWP), osmotic potential (ψs), leaf relative conductivity (REC), leaf proline content (Pro), leaf and root soluble protein contents (LSPC and RSPC), leaf and root malondialdehyde (MDA) contents (LMDA and RMDA), root superoxide dismutase, peroxidase, and catalase activities (RSOD, RPOD, and RCAT) were measured. Results indicated the 18 physiological indices can be converted into five or six independent comprehensive indices by principal component analysis, and nine typical indices (F_v/F_m, SWC, LWP, Pro, LMDA, RSPC, RMDA, RSOD, and RCAT) screened out by a stepwise regression method could be utilized to evaluate the drought resistance. Moreover, the 16 cotton cultivars were divided into four types: drought sensitive, drought weak sensitive, moderate drought resistant, and drought resistant types. The resistance ability of two selected cotton cultivars (drought resistant cultivar, Dexiamian 1; drought sensitive cultivar, Yuzaomian 9110) with contrasting drought sensitivities were further verified by pot experiment. Results showed that the responses of final cotton biomass, yield, and yield composition to drought were significantly different between the two cultivars. In conclusion, drought resistant cultivar Dexiamian 1 and drought sensitive cultivar Yuzaomian 9110 were screened through hydroponics experiment, which can be used as ideal experimental materials to study the mechanism of different cotton cultivars with contrasting drought sensitivities in response to drought stress.