Additive genes in wheat for resistance to stripe (yellow) rust (Puccinia striiformis Westend.)

Forty-nine lines of wheat (F₆ generation) containing minor additive genes conditioning resistance to stripe (yellow) rust (Puccinia striiformis Westend.) were evaluated to several virulence types (physiologic races) of the pathogen obtained from the USA and Europe. All wheat lines showed some level of resistance to all virulence types of P. striiformis but there were differences in level of resistance between crosses and between lines within a particular cross. Generally, all lines expressed the most resistance at the seedling stage when grown at higher temperatures (15°C during the dark period; 25°C during the light period) than at 2°C (dark period) and 20°C (light period). Lines with more resistance genes showed the most resistance, and this resistance was least sensitive to temperature change. Mature plants in the field had levels of resistance equal to, or greater than, those of their seedling counterparts. One parent of each cross evaluated was either a commercial cultivar or an advanced wheat selection, and was rated as susceptible. In many cases, these susceptible parents contributed to resistance in the progeny and thus the progeny showed transgressive segregation for resistance. Some parent cultivars, which were completely susceptible as seedlings and moderately resistant as mature plants, also contributed to seedling resistance in the progeny when combined with parents known to contain minor additive genes for resistance to P. striiformis. The advantages of using minor additive genes are discussed in relation to the control of stripe rust of wheat and to crop protection generally.     

Mapping of wheat stripe rust resistance gene Yr041133 by BSR-Seq analysis

Puccinia striiformis Westend. f. sp. tritici(Pst) pathotype CYR34 is widely virulent and prevalent in China.Here, we report identification of a strpie rust resistance(Yr) gene, designated Yr041133, in winter wheat line 041133. This line produced a hypersensitive reaction to CYR34 and conferred resistance to 13 other pathotypes. Resistance to CYR34 in line 041133 was controlled by a single dominant gene. Bulked segregant RNA sequencing(BSR-Seq) was performed on a pair of RNA bulks generated by pooling resistant and susceptible recombinant inbred lines. Yr041133 was mapped to a 1.7 c M genetic interval on the chromosome arm 7 BL that corresponded to a 0.8 Mb physical interval(608.9–609.7 Mb) in the Chinese Spring reference genome. Based on its unique physical location Yr041133 differred from the other Yr genes on this chromosome arm.     

Fine mapping and transcriptome sequencing reveal candidate genes conferring all-stage resistance to stripe rust on chromosome arm 1AL in Chinese wheat landrace AS1676

Stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), threatens wheat production worldwide, and resistant varieties tend to become susceptible after a period of cultivation owing to the variation of pathogen races. In this study, a new resistance gene against Pst race CYR34 was identified and predicted using the descendants of a cross between AS1676, a highly resistant Chinese landrace, and Avocet S, a susceptible cultivar. From a heterozygous plant from a F7recombinant inbred line(RI...     

Bread wheat cultivar PBW 343 carries residual additive resistance against virulent stripe rust pathotype

With continuous outbreaks of stripe rust (Puccinia striiformis f. sp. tritici) epidemics and rapid breakdown of deployed resistance in bread wheat (Triticum aestivum L.) cultivars in North West Plains Zone (NWPZ) in India warrant knowledge and deployment of new and durable sources of resistance to stripe rust. Bread wheat cultivar PBW 343, until recently the most widely cultivated wheat variety in India, is now highly susceptible to stripe rust (score 9 on a 1–9 scale), whereas PBW 621 (score 5.05–5.65) and HD 2967 (score 5.40–6.20) show low levels of resistance. We conducted an experiment, spanning three crop seasons (2013–2014 to 2015–2016), in which parental lines, F₁ and F₂ populations, F₃ and F₄ families from two bread wheat crosses, PBW 621/PBW 343 and HD 2967/PBW 343 were generated and evaluated for stripe rust resistance against a virulent pathotype. While the F₁ revealed partial dominance, the segregation pattern for stripe rust resistance in F₂ and F₃ showed transgressive segregation for resistance in both crosses. Chi-square analysis indicated that resistant segregants possessed two genes, one contributed by PBW 621 or HD 2967 (depending on the cross) and the other, unexpectedly but obviously, came from the most susceptible cultivar, PBW 343. Possible genetic mechanisms for this residual resistance and implications for breeding programs are discussed.     

TaARPC5 is required for wheat defense signaling in response to infection by the stripe rust fungus

Numerous studies using a combination of confocal microscopic-and pharmacological-based approaches have demonstrated that the actin cytoskeleton dynamically responds to pathogen infection.Here,we observed that phalloidin treatment induced actin nucleation,resulting in enhanced resistance of wheat against the stripe rust pathogen Puccinia striiformis f.sp.tritici(Pst).To define the mechanism underpinning this process,we characterized a family of conserved actin-binding proteins,the actin related protein(ARP)family,which controls actin polymerization.Specifically,we identified and characterized a wheat ARPC gene(Ta ARPC5),which encodes a 136-amino acid protein containing a P16-Arc domain,the smallest subunit of the ARP2/3 complex.Ta ARPC5 m RNA accumulation was induced following the infection of plants with the avirulent Pst strain,and following the elicitation with flagellin(e.g.,flg22)as well.Subcellular localization analysis revealed that Ta ARPC5 is primarily localized to the cortical actin cytoskeleton,and its precise cellular localizations suggest the proximity to processes correlated with the actin-organelle interface.Upon treatment with virulent Pst,Ta ARPC5-knockdown plants exhibited a significant reduction in the expression of PTI-specific m RNAs.Conversely,we observed enhanced induction of reactive oxygen species(ROS)accumulation and a decrease in Ta CAT1 expression following infection with an incompatible Pst isolate.Together with yeast complementation assays,the current study demonstrates a role for Ta ARPC5 in resistance signaling in wheat against Pst infection by regulating the host actin cytoskeleton.     

Effects of fungicides applied at seeding on stripe rust and common bunt of wheat

Control of stripe rust (Puccinia striiformis) and common bunt (Tilletia caries and T. foetida) of wheat (Triticum aestivum), with fungicides applied on or adjacent to seed at sowing, was studied. Etaconazole pellets (2800 g a.i./ha), fenfuram liquid seed treatment (17 · 5 g a.i./ha) and imazalil granules (5000 g a.i./ha) were phytotoxic, reducing the number of heads per plot. All treatments reduced the incidence of common bunt although benomyl granules (2500 g a.i./ha), benomyl pellets (1400 g a.i./ha) and imazalil granules (5000 g a.i./ha) were not as effective as the registered smut fungicides carboxin, fenfuram, fenaminosulf and triadimefon. Triadimefon pellets (7000 g a.i./ha), PP347 pellets (1400 g a.i./ha), triadimefon granules (1500 g a.i./ha), flutriafol pellets (1400 g a.i./ha) and etaconazole pellets (2800 g a.i./ha) reduced stripe rust severity 17 weeks after sowing by 90, 89, 88, 86 and 74%, respectively.     

Genetic resistance to and effect of leaf rust and powdery mildew on yield and its components in 50 soft red winter wheat cultivars

Effects of leaf rust (caused by Puccinia triticina f. sp. tritici Eriks.) and powdery mildew [caused by Blumeria graminis (DC.) E. O. Speer f. sp. tritici Em. Marchal], on performance of 50 soft red winter (SRW) wheat (Triticum aestivum L) cultivars were evaluated under natural field conditions. Widely grown cultivars released from 1919 to 2009 with varying disease resistance were grown in split-plot experiments in 2010 and 2011. Treated replications received seed treatments of triadimenol, captan and imidacloprid and foliar applications of propiconazole and prothioconazole + tebucanazole fungicides. Non-treated replications received only tebucanazole + metalaxyl + imazalil seed treatments. Final mean disease severity, agronomic, yield-related traits, yield components and spike characteristics were analyzed to determine individual and combined effects of leaf rust and powdery mildew on the cultivars. Yield losses as high as 54% were observed in the susceptible cultivar Red May. Average yield losses ranged from 1% to 21%. Yield losses primarily due to powdery mildew were as high as 14%, and losses primarily due to leaf rust were as high as 33%. Powdery mildew had the largest negative correlation with harvest index and seeds/spike. Leaf rust was most negatively correlated with plant biomass and harvest index, with a less consistent negative relationship with kernel weight.     

Combined linkage and association mapping reveals two major QTL for stripe rust adult plant resistance in Shaanmai 155 and their haplotype variation in common wheat germplasm

The development and deployment of diverse resistance sources in new wheat cultivars underpin the durable control of stripe rust. In the present study, two loci for adult plant resistance(APR),QYr SM155.1 and QYr SM155.2, were identified in the Chinese wheat breeding line Shaanmai 155.QYr SM155.1 was mapped to a 3.0-c M interval between the single-nucleotide polymorphism(SNP) markers AX-109583610 and AX-110907562 on chromosome arm 2 BL. QYr SM155.2 was mapped to a 2.1-c M interval flanked by the ...     

我国部分地区小麦生产品种和后备品系抗秆锈病状况分析

2008-2009年间对来自我国小麦主要生产种植区15个省份的182份小麦生产品种和后备品系进行了苗期与成株期抗秆锈病鉴定,研究结果表明：在供试的品种（系）中,114份对秆锈病表现抗性,占供试材料的62.64%,其中来自东北春麦区、北方冬麦区和黄淮海冬麦区的品种（系）对秆锈病抗性较强,部分地区材料对秆锈病的抗性较差,甚至江苏省的13份品种（系）对秆锈病全部感病,这表明虽然我国当前小麦生产品种和后备品系对秆锈病的抗性普遍较强,但仍然存在有相当数量的感病品种,秆锈病发生与流行的威胁依然存在。     

淮安市楚州区小麦条纹叶枯病发生原因及防治对策初探

淮安市楚州区位于苏北灌溉总渠与京杭大运河交界处。农作物以稻麦连作为主,一年两熟制,是江苏省主要粮食产区。近几年来由于水稻条纹叶枯病在江淮地区暴发流行,灰飞虱越冬残留量大、带毒率高,水稻条纹叶枯病与小麦条纹叶枯病为同一病毒所致。两种病害产生相互影响效应,     

大麦染色体特异性EST标记在5H短臂成株期叶锈病抗性基因定位中的应用

为了明确大麦成株叶锈病抗性品种‘Pompadour’抗性基因的性质,以‘WABAR2482×Pompa-dour’的457个F2后代为材料,采用单链构象多态性(SSCP)分析技术,对发掘的SNP-EST分子标记在抗性品种的F2后代中进行分子标记检测。结果表明,457株F2分离群体中328株表现抗病,129株表现感病,卡方检验符合3∶1的分离比例。推断新发现的5HS成株叶锈病抗性基因为主效显性抗性基因。在所筛选的15对大麦5HS染色体EST标记中,共显性SNP标记K05820共检测出109株抗性亲本纯合体、115株感病亲本纯合体和233株杂合体。利用F2代表型分离结果对标记K05820进行验证分析发现,该标记与‘Pompa-dour’5HS染色体成株叶锈病抗性高度相关(r=0.82)。同时,新的定位分析表明,K05820与成株叶锈病抗性基因间的遗传距离为7 cM。这说明共显性EST-SNP标记K05820可以运用于大麦5HS染色体成株叶锈病抗性基因后代杂合体及纯合体的筛选,能够应用于田间抗病材料的初步筛选。     

Model of stripe rust infection and control on irrigated wheat in the murrumbidgee irrigation areas of new South Wales

A well-developed epidemic of stripe rust on a field crop of a susceptible wheat cultivar (cv. Avocet) led to significant yield reductions compared to plots which were protected with regular applications of the fungicide triadimefon (Bayleton®). A modified logistic transformation of the leaf infection data provided values of apparent infection rate, r, which are required for use in simulation models of disease progress and predicted yield loss, such as epidemic and epipre. Flagleaf area at early water stage of the kernels (86 days following sowing, DFS; Zadoks growth stage 70), afforded a good prediction of grain yield. Stripe rust infection of the flag leaf had a strong negative effect on final grain yields larger than would have been predicted solely from a loss of photosynthetic area. Flood irrigation did not affect the level of disease on the flag leaf at 86 DFS nor the apparent infection rate of stripe rust on the flag leaf. Irrigation gave increased grain yield only in sprayed treatments. Conversely, while there was a yield response due to fungicide application to cv. Avocet in both irrigated and non-irrigated plots, the cost benefit of spraying the latter was marginal.     

Biological control of wheat stripe rust by an endophytic Bacillus subtilis strain E1R-j in greenhouse and field trials

Endophytic Bacillus subtilis strain E1R-j, isolated from wheat roots, inhibits a wide range of microorganisms. In this study, we determined its inhibitory effect on urediniospore germination of Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust and biocontrol effect on the rust development using bacterial cell suspension (BCS) and fermentation liquid with and without bacterial cells (FLBC and FL). Urediniospore germination was significantly inhibited by all three formulations in vitro. The maximum inhibition rate was 84.1% treated with the 10-fold dilution of original formulation of FLBC. Microscopic observation revealed that the bacterial treatments caused urediniospores and germ tubes ruptured, which resulted in protoplasm release and dysfunction of fungal structures. Urediniospore germination was also significantly inhibited by spraying E1R-j on leaf surface before inoculation. Formulations FLBC and FL were both better than formulation BCS. In a condition-controlled greenhouse, application of FLBC and FL 24 and 0 h before Pst inoculation displayed a protective mode in reducing disease severity, and the control efficacy was between 54.0% and 87.7%. For formulation BCS, only the application of 24 h before Pst inoculation significantly reduced rust severity with control efficacy 51.8%. The incidence of diseased leaves in the treatments of FLBC and FL were significantly reduced compared to the non-treated plots in the field experiments conducted in the season 2007–2008. The control efficacy was 51% and 43% for the two treatments, respectively. This study is helpful for further developing a biocontrol approach for managing stripe rust.     

高蛋白、多抗、高产花生新品种粤油79的选育

粤油79是广东省农业科学院作物研究所采用一粒传法选育而成的高蛋白、多抗花生新品种。粤油79在广东省花生区域试验和国家南方花生品种区域试验中，产量均比对照种汕油523增产，并表现高抗青枯病、抗锈病和叶斑病。粤油79蛋白质含量为32．23％，油酸／亚油酸比值1．67。1999年通过广东省农作物审定委员会审定，2002年通过全国农作物审定委员会审定。     

我国主要麦区101个小麦生产和区试品种（系）及高代品系抗白粉基因推导

为了明确我国小麦品种（系）中抗白粉基因的组成,利用基因推导法对来自我国主要麦区的101个小麦品种（系）进行了抗白粉病基因推导。结果表明,近一半的供试生产品种对所有供试菌株表现感病;供试的大多数区试品种具有有效地抗白粉基因,应加快这些抗病品种的大面积推广;近1/3的高代品系含有有效地抗白粉基因。供试小麦生产品种和区试品种（系）及高代品系中具有已知的抗白粉基因主要有Pm4b、Pm8、Pm2 Mld、Pm4a、Pm2、Pm2 6、Pm30等。此结果对于我国小麦白粉病的抗病育种和品种布局有重要的参考价值。     

Evaluation of soybean for resistance to soybean rust in Vietnam

Soybean rust, caused by Phakopsora pachyrhizi Sydow, is a severe foliar disease of soybean [Glycine max (L.) Merr.] that occurs throughout most soybean producing regions of the world. The objective of this research was to evaluate selected soybean genotypes for resistance to soybean rust in Vietnam. Five field experiments in Vietnam were completed from 2006 to 2009. The area-under-the-disease-progress-curve (AUDPC) was calculated for each soybean genotype based on four disease assessments taken during the reproductive growth stages. AUDPC units among soybean genotypes in each experiment differed (P < 0.05). Over the five experiments, the resistant check DT 2000 was most often the genotype with the lowest AUDPC units while the sources of rust resistance (Rpp1-5) did not always have low AUDPC units in each experiment, although PI 230970 (Rpp2) appeared to be more stable. A few genotypes with non-characterized genes for resistance, such as PI 398998, PI 437323, and PI 549017, had the lowest AUDPC units in at least one of the experiments. These genetic resources may be useful for host plant resistance studies and breeding soybeans for rust resistance in Vietnam and other locations like Brazil and the United States that have more recently been inundated with soybean rust. A significant (P < 0.001) experiment × genotype interaction was found when the AUDPC data of 14 soybean genotypes tested in Experiments 1, 2, and 3 were combined and analyzed. This result indicates the potential importance of changing fungal races and/or biotypes that occur in the rust population.     

Fungicidal control of groundnut leaf spot and rust in Nigeria

Four systemic fungicide formulations (tridemorph, tridemorph plus maneb, carbendazim and benomyl) and three non-systemic fungicides (captafol, mancozeb and copper oxychloride) were evaluated in field trials at two locations in Nigeria in 1981 and 1982 for control of early leaf spot (Mycosphaerella arachidis Deighton, stat: conid: Cercospora arachidicola Hori), late leaf spot (Mycosphaerella berkleyi W. A. Jenkins, stat: conid: Cercosporidium personatum (Berk. & Curt.) Deighton) and rust (Puccinia arachidis Speg.) of groundnut (Arachis hypogaea L.). Plots receiving mancozeb and tridemorph plus maneb showed best overall disease control and highest yields, followed by copper oxychloride. Benomyl and carbendazim controlled leaf spots predominantly while tridemorph controlled only rust. Captafol gave little overall disease control with yields only slightly better than untreated controls. Further tests are planned for tridemorph plus maneb and copper oxychloride using different concentrations and spray schedules.     

Gibberellin-sensitive Rht alleles confer tolerance to heat and drought stresses in wheat at booting stage

The present study compared six near-isogenic lines from different backgrounds, varying in Rht (reduced height) alleles for gibberellin (GA) response, for heat and drought tolerance. Various temperature (day/night: 20/12 °C to 39/31 °C), and irrigation (100% field capacity and no irrigation) treatments were imposed at booting stage. Results depicted a 50% reduction in grain yield at 36.7 °C with irrigation and at 31.2 °C without irrigation. Number of grains per spike was severely reduced over 26 °C for water-stressed plants while irrigated plants did not show any significant reduction up to 34 °C. Ear numbers per pot and spikelets per spike were unaffected by irrigation till 33 °C. In Mercia, grain nitrogen, sulphur, and Hagberg falling number (HFN) were significantly higher for severe dwarfs (Rht-D1c and Rht-12), however, in Maris Widgeon, rht (tall) recorded higher nitrogen and sulphur concentration while Rht-B1b presented the maximum sedimentation of sodium dodecyl sulphate (SDS). The SDS was higher in Maris Widgeon while HFN were superior in Mercia. Conclusively, the present study demonstrated that heat and drought stresses severely reduced the grain yield while improved grain quality traits. The GA-insensitive semi dwarf Rht-B1b was the most promising genotype for grain yield and HFN under combined drought and heat stresses.     

Developmental patterns in wheat and resistance to cereal aphids

As wheat develops it varies in its suitability for the grain aphid, Sitobion avenae, so the duration of each developmental stage determines aphid population growth. Simulations of aphid population development on spring and winter wheat cultivars revealed that, as the length of the preferred earing phase was found to be relatively constant, peak population size is determined by the number of aphids at ear emergence. This can be reduced by growing early-maturing varieties, which in terms of crop developmental stage effectively delays the start of the spring migration. Breeding wheat that matures as early as winter barley would greatly reduce the number of aphid outbreaks and make the prophylactic spraying of insecticides unnecessary.     

Host genes and transgenes that confer resistance to a Scottish isolate of potato leafroll virus are also effective against a Peruvian isolate

Summary Potato genotypes with host gene-mediated resistance (host-MR) and coat protein-mediated transgenic resistance (CP-MR) to potato leafroll virus (PLRV), were inoculated with a Scottish and a Peruvian isolate of PLRV. The coat protein transgene had been cloned from the Scottish PLRV isolate which had also been used during the screening and selection of genotypes with host resistance. Significantly less PLRV accumulated in plants with either host-MR or CP-MR than in plants of susceptible genotypes or in non-transformed control plants, but the two forms of resistance were equally effective against both PLRV isolates.