STUDIES ON THE PHYSIOLOGIC SPECIALIZATION OF YELLOW RUST (PUCCINIA GLUMARUM (SCHM.) ERIKSS. & HENN.) IN GREAT BRITAIN

During 1945-8, 223 British collections of yellow rust were determined on Gassner & Straib's differential hosts, with the addition of the wheat variety Wilma. Physiologic races 2, 3, 5, 6, 7, 8 and 17 were obtained from wheat, race 46 from barley, race 33 from Hordeum murinum and race 28 from Agropyron repens. Three new races, 6x from wheat, M from H. marinum and G from Dactylis glomerata were also isolated. High temperatures increase the susceptibility of some differential hosts to certain wheat races, but decrease that of others. Biotypes of races 2, 6 and 8, differing from the 'type' cultures of those races, were isolated.
Of the commoner wheat races, nos. 6 and 8, occurring on many wheats, were widespread, but races 5 and 7, on fewer varieties, were confined to the north of Britain, and races 2 and 3, on very few varieties, to the south. Certain grasses are partially susceptible to some of the cereal races. The uredospores of race 2 germinate less well than those of races 5 or 8, other wheat races being intermediate. The optimum temperature for spore germination of race G is 22-5 C, that of all other races 10–13^oC.
Twelve wheat varieties were inoculated in the field with each of the eight wheat races, and some varieties developed field resistance to certain races. The races attacking a variety the most severely in the field inoculations were usually the races isolated from that variety in collections received.     

2003-2013年小麦品种(系)抗条锈性鉴定及评价

2003-2013年在甘肃省农业科学院植物保护研究所兰州温室和甘谷试验站,分别对来自国内35个相关育种单位的冬春小麦品种(系)5001份,其中冬小麦4291份、春小麦710份,进行苗期混合菌、成株期分小种和混合菌抗条锈性接种鉴定,结果表明:全生育期表现免疫近免疫的有兰天31号等479份,高抗的有兰天23号等76份,中抗的有天选49等291份,分别占9.58％、1.52％和5.82％;成株期表现免疫近免疫的有天选50号等840份,高抗的有兰天27号等47份,中抗的有天选52等311份,分别占16.80％、0.94％和6.22％;苗期表现免疫近免疫的有兰天30号等964份,高抗的有天98102等122份,中抗的有00-30等273份,分别占19.28％、2.44％和5.46％.冬小麦有天选49号等914份材料表现全生育期抗病,占18.28％;有97-473等906份成株期表现抗病,占18.12％;有兰天20号等1225份苗期表现抗病,占24.50％.春小麦有定西41号等113份材料全生育期表现抗病,占2.26％;有陇春28号等125份成株期表现抗病,占2.50％;有0109-1等114份苗期对混合菌表现抗病,占2.28％.先后在甘肃天水汪川良种场对相关材料进行成株期抗条锈性评价,结果发现:1154份从小种圃筛选出的抗病材料中,表现抗病的有兰天31号等745份,占64.56％;105份甘肃陇南生产品种中,到2013年表现抗病的仅有兰天28号、中梁31号等30份材料,占28.57％;后备品系中,00-30-2-1、CP04-20、00127-2-3等抗性表现优异;抗源材料中,仅有贵农775、中四、T.Spelta albun、贵协1、贵协3等少数材料表现抗病,重要抗源材料贵农21、贵农22、南农92R、川麦42、Moro从2011年开始在田间表现感病,逐步失去利用价值.其衍生系品种材料如陇鉴9343、天选43号、中梁29号、兰天17号、兰天24号等也在田间逐步感病,条锈病发生流行压力持续增大.     

1994 - 2002年小麦品种(系)抗条锈性鉴定与监测

1994—2002年经对3822份小麦品种(系)材料抗条锈性鉴定结果表明,冬小麦抗条锈性优于春小麦,甘肃品种抗条锈性优于国内其它省区品种。田间抗条锈性监测结果表明,我国主要生产品种均表现感病,甘肃主要生产品种仅陇鉴127等少数几个品种抗病,抗源材料中也仅有中四等少数品种表现抗病,结合抗病性鉴定、监测结果及田间综合农艺性状观察,筛选出20余份可供育种利用的抗源材料。同时在针对今后抗条中31、32号等主要小种类型的抗病育种、抗病性监测等方面进行了讨论。     

黄淮麦区重要小麦品种和种质资源材料的抗条锈性评价

采用苗期分小种和成株期混合优势小种法测定了黄淮麦区227份小麦品种和种质材料对小麦条锈菌的抗病性,结果表明,被测品种在苗期对4个条锈菌生理小种的抗病性有很大的差异,抗条中27、30、31、29号小种的品种分别占被测品种总数的93．00%、72．69%、64．76%和61．67%。成株期用6个菌株混合接种测定选出抗病品种76个,占33．48％,其中免疫的为40个,占17．62%。通过对227份小麦品种资源材料的苗期分小种鉴定及与成株期混合优势小种鉴定结果比较,筛选出了成株期和苗期均抗病的品种48个,占被测品种总数的21．14％;成株期抗病苗期感病的品种30个,占被测品种总数的13．22％。     

中国小麦生产上年种植面积超66.7万hm2的品种及其分析

中国在1950～2000年期间,小麦生产上年种植面积超66.7万hm2的品种共53个.对这53个品种的分析结果表明,有6个原产国外,本国的品种主要是河南、山东、四川、陕西、河北等省市的;除2个地方品种外,其它品种的亲本间都是地理远缘的或有地理远缘血统的;随年代的推移,品种的数量逐渐增多,而最大年种植面积和单个品种种植地区逐渐减少,这些变化是我国小麦育种水平提高的结果.     

PHYSIOLOGIC RACES OF PHYTOPHTHORA INFESTANS (MONT.) DE BARY IN NORTHERN IRELAND*

By using the detached-leaf technique and Black's series of differential host varieties, seven physiologic races of Phytophthora infestans (Mont.) de Bary have been distinguished as occurring in Northern Ireland. Six were found at the Dunanney potato variety trial plots, namely: race 1; race 2; race 4; race I, 2; race 1,4; and race I, z, 4. The remaining race, race 0, was isolated from the commercial potato crop.
In a survey, comprising seventy-three isolates, of the physiologic races occurring in the commercial potato crop, only race o and race 4 were found (3 and 70 isolates respectively).
Certain modifications to the detached-leaf technique have given improved results, including the formation of normal lesions and the elimination of atypical infections showing sparse sporulation.
The variation in the host-parasite reaction of the detached leaves and the identity of the common race in commercial potato crops are discussed.     

Physiologic specialization of Colletotrichum corchori,Ikata and Yoshida,the causal organism of anthracnose of jute (Corchorus capsularis L.)

Summary Four varieties of jute,Corchorus capsularis, among fifteen screened were found to differentiate six races ofColletotrichum corchori. As regard virulence only two races, CS-1 and CS-2 among the six were of real importance.Besides recognising six races on four differential jute varieties, these were also differentiated from their cultural and morphological studies on laboratory medium as six cultural races.     

Identification of quantitative trait loci for race-nonspecific resistance to tan spot in wheat

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is an economically important foliar disease in the major wheat growing areas throughout the world. Multiple races of the pathogen have been characterized based on their ability to cause necrosis and/or chlorosis on differential wheat lines. In this research, we evaluated a population of recombinant inbred lines derived from a cross between the common wheat varieties Grandin and BR34 for reaction to tan spot caused by Ptr races 1–3 and 5. Composite interval mapping revealed QTLs on the short arm of chromosome 1B and the long arm of chromosome 3B that were significantly associated with resistance to all four races. The effects of the two QTLs varied for the different races. The 1B QTL explained from 13% to 29% of the phenotypic variation, whereas the 3B QTL explained from 13% to 41% of the variation. Additional minor QTLs were detected but not associated with resistance to all races. The host-selective toxin Ptr ToxA, which is produced by races 1 and 2, was not a significant factor in the development of disease in this population. The race-nonspecific resistance derived from BR34 may take precedence over the gene-for-gene interaction known to be associated with the wheat–Ptr system.     

C4 Photosynthesis (The CO2-Concentrating Mechanism and Photorespiration)

Despite previous reports of no apparent photorespiration in C4 plants based on measurements of gas exchange under 2 versus 21% O2 at varying [CO2], photosynthesis in maize (Zea mays) shows a dual response to varying [O2]. The maximum rate of photosynthesis in maize is dependent on O2 (approximately 10%). This O2 dependence is not related to stomatal conductance, because measurements were made at constant intercellular CO2 concentration (Ci); it may be linked to respiration or pseudocyclic electron flow. At a given Ci, increasing [O2] above 10% inhibits both the rate of photosynthesis, measured under high light, and the maximum quantum yield, measured under limiting light ([phi]CO2). The dual effect of O2 is masked if measurements are made under only 2 versus 21% O2. The inhibition of both photosynthesis and [phi]CO2 by O2 (measured above 10% O2) with decreasing Ci increases in a very similar manner, characteristically of O2 inhibition due to photorespiration. There is a sharp increase in O2 inhibition when the Ci decreases below 50 [mu]bar of CO2. Also, increasing temperature, which favors photorespiration, causes a decrease in [phi]CO2 under limiting CO2 and 40% O2. By comparing the degree of inhibition of photosynthesis in maize with that in the C3 species wheat (Triticum aestivum) at varying Ci, the effectiveness of C4 photosynthesis in concentrating CO2 in the leaf was evaluated. Under high light, 30[deg]C, and atmospheric levels of CO2 (340 [mu]bar), where there is little inhibition of photosynthesis in maize by O2, the estimated level of CO2 around ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the bundle sheath compartment was 900 [mu]bar, which is about 3 times higher than the value around Rubisco in mesophyll cells of wheat. A high [CO2] is maintained in the bundle sheath compartment in maize until Ci decreases below approximately 100 [mu]bar. The results from these gas exchange measurements indicate that photorespiration occurs in maize but that the rate is low unless the intercellular [CO2] is severely limited by stress.     

THE REACTION OF WHEAT VARIETIES TO LOOSE SMUT AS DETERMINED BY EMBRYO, SEEDLING, AND ADULT PLANT TESTS

The possibility of using an embryo test as a means of determining the reaction of wheat varieties to loose smut ( Ustilago tritici (Pers.) Rostr.) has been investigated. Fifty-seven varieties were inoculated with two physiologic races by the partial vacuum method and the embryos, seedlings, and adult plants were examined for infection. Most of the varieties were fully susceptible to one or both races, and only ten showed real resistance to any one race. Braun R and Molinel proved almost immune to infection. The resistance in other varieties which showed no infection in the field was expressed as embryo susceptibility, i.e. the embryo became infected in much the same way as in field-susceptible varieties.
In the latter varieties infection passes from the embryo into the growing point of the young seedling. In the embryo-susceptible field-resistant varieties, infection does not pass from the scutellum and the growing point is therefore uninfected.
The reaction of most of the varieties tested was straightforward resistance or susceptibility, but in a few varieties a small proportion of the grains reacted differently from the majority. These reactions are discussed.     

Contribution of indole alkaloids to Sitobion avenae (F.) resistance in wheat

Abstract:  Indole alkaloid contents of five winter wheat varieties at different growth stages, and the relationship between indole alkaloids and carboxylesterase activities of Sitobion avenae (F.) from wheat ears of different varieties were studied. The results indicated that KOK1679 and My295, highly and moderately aphid-resistant varieties, had a high indole alkaloid content during vegetative growth. During their reproduction growth, resistant varieties had a high alkaloid content in penultimate leaves, and indole alkaloid contents of KOK1679 were significantly higher than that of other varieties in wheat ears. The indole alkaloid contents of all varieties were low in flag leaves except for Han4564 . A significant correlation was shown between carboxylesterase activity in aphids collected from wheat ears and indole alkaloid contents in ears of the wheat varieties ( r  = 0.9646).     

QTL mapping of resistance to race Ug99 of Puccinia graminis f. sp. tritici in durum wheat (Triticum durum Desf.)

Stem rust caused by Puccinia graminis f. sp. tritici was historically one of the most destructive diseases of wheat worldwide. The evolution and rapid migration of race TTKSK (Ug99) and derivatives, first detected in Uganda in 1999, are of international concern due to the virulence of these races to widely used stem rust resistance genes. In attempts to identify quantitative trait loci (QTL) linked with resistance to stem rust race Ug99, 95 recombinant inbred lines that were developed from a cross between two durum wheat varieties, Kristal and Sebatel, were evaluated for reaction to stem rust. Seven field trials at two locations were carried out in main and off seasons. In addition to the natural infection, the nursery was also artificially inoculated with urediniospores of stem rust race Ug99 and a mixture of locally collected stem rust urediniospores. A genetic map was constructed based on 207 simple sequence repeat (SSR) and two sequence tagged site loci. Using composite interval mapping, nine QTL for resistance to stem rust were identified on chromosomes 1AL, 2AS, 3BS, 4BL, 5BL, 6AL 7A, 7AL and 7BL. These results suggest that durum wheat resistance to stem rust is oligogenic and that there is potential to identify previously uncharacterized resistance genes with minor effects. The SSR markers that are closely linked to the QTL can be used for marker-assisted selection for stem rust resistance in durum wheat.     

杂交后代中转基因小麦外源1Ax1基因的遗传

高分子量麦谷蛋白亚基1Ax1基因是决定小麦加工品质的主效基因之一,在小麦胚乳中增加1Ax1基因的表达量可以提高其加工品质,这对于小麦的品质改良具有重要意义。采用外源1Ax1基因超量表达的转基因小麦‘B102-1-2’为父本,常规小麦品种‘鄂麦12’和‘川89-107’为母本进行杂交试验。采用SDS-PAGE技术检测并分析各组合亲本、F1代、F2代的HMW-GS组成,从而研究转基因小麦‘B102-1-2’中外源品质基因1Ax1表达的遗传规律。研究结果表明:外源基因有效地整合进入主栽小麦的基因组中,并且正确表达,在F2代中表现出15∶1的分离比,遵循孟德尔遗传模式,这对于杂交育种策略的选择制订具有指导意义。     

The genetics of resistance to five races of downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.)

 These studies were undertaken to determine whether downy mildew resistance genes in sunflower were independent as first reported, or linked as suggested by more recent hypotheses. The segregations for downy mildew reaction of 111 F₃ progenies from a cross between a susceptible line and a line with Pl2 were used to locate this gene on the sunflower consensus RFLP linkage map. It was shown that Pl2 was linked to the same RFLP markers on linkage group 1 as Pl1 and Pl6, mapped earlier, and at a very similar distance. The F₃ progenies showed exactly the same segregation patterns when tested with race 1 and race D. One hundred and fifty four progenies from a cross between a susceptible line and HA335, containing Pl6 (considered as giving resistance to all Plasmopara halstedii races), were tested with the five French downy mildew races, 1, A, B, C and D. Two progenies were observed to show segregation for races 1 and D, while appearing homozygous-resistant to races A , B and C. Tests on F₄ progenies confirmed this separation of resistances with fixation of susceptibility to races 1 and D and resistance to races A, B and C. It is concluded that the Pl6 gene is not a “strong” gene, giving resistance to all downy mildew races, but rather a cluster of genes, each providing resistance to one, or a few, downy mildew races. The genes giving resistance to races 1 and D, on one hand, and to races A, B and C, on the other hand, must be very closely linked, with about 0.6 cM between the two groups. Received: 23 December 1996 / Accepted: 18 April 1997     

Physiologic specialisation in Macrophomina phaseoli (Maubl.) Ashby., causing stem rot of jute,corchorus species

With eight isolates ofMacrophomina phaseoli, pathogenicity test was conducted on twenty varieties of jute belonging to two species,Corchorus capsularis andC. olitorius. Against six isolates the varieties screened showed different degrees of disease reactions while against the remaining two, all the varieties gave similar resistant reaction. As differential varieties, a minimum of four recognised the seven physiological races ofMacrophomina phaseoli. From the cultural characteristics, however, all the eight isolates differed from each other and were fitted in a dichotomous key as eight cultural races.

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Zusammenfassung Mit acht Stämmen vonMacrophomina phaseoli sind Pathogenitätstest an zwanzig Varietäten von Jute durchgeführt worden, die zwei Arten:Corchorus capsularis undC. olitorius angehören. Gegen sechs Stämme zeigten die untersuchten Varietäten einen verschiedenen Grad der krankhaften Reaktionen, während gegen die restlichen zwei Stämme alle Varietäten gleichartige Widerstandsfähigkeit aufwiesen. Mindestens vier von den sieben physiologischen Rassen vonM. phaseoli sind erkannt worden. Betreffs der Kulturcharakteristik wichen alle acht Stämme von einander ab und sind als echte Kulturrassen beschrieben.

     

Whole Genome Association Mapping of Plant Height in Winter Wheat (Triticum aestivum L.)

The genetic architecture of plant height was investigated in a set of 358 recent European winter wheat varieties plus 14 spring wheat varieties based on field data in eight environments. Genotyping of diagnostic markers revealed the Rht-D1b mutant allele in 58% of the investigated varieties, while the Rht-B1b mutant was only present in 7% of the varieties. Rht-D1 was significantly associated with plant height by using a mixed linear model and employing a kinship matrix to correct for population stratification. Further genotyping data included 732 microsatellite markers, resulting in 770 loci, of which 635 markers were placed on the ITMI map plus a set of 7769 mapped SNP markers genotyped with the 90 k iSELECT chip. When Bonferroni correction was applied, a total of 153 significant marker-trait associations (MTAs) were observed for plant height and the SSR markers (−log₁₀ (P-value) ≥4.82) and 280 (−log₁₀ (P-value) ≥5.89) for the SNPs. Linear regression between the most effective markers and the BLUEs for plant height indicated additive effects for the MTAs of different chromosomal regions. Analysis of syntenic regions in the rice genome revealed closely linked rice genes related to gibberellin acid (GA) metabolism and perception, i.e. GA20 and GA2 oxidases orthologous to wheat chromosomes 1A, 2A, 3A, 3B, 5B, 5D and 7B, ent-kaurenoic acid oxidase orthologous to wheat chromosome 7A, ent-kaurene synthase on wheat chromosome 2B, as well as GA-receptors like DELLA genes orthologous to wheat chromosomes 4B, 4D and 7A and genes of the GID family orthologous to chromosomes 2B and 5B. The data indicated that besides the widely used GA-insensitive dwarfing genes Rht-B1 and Rht-D1 there is a wide spectrum of loci available that could be used for modulating plant height in variety development.     

Rust resistance in Triticum cylindricum Ces. (4x, CCDD) and its transfer into durum and hexaploid wheats.

In order to counteract the effects of the mutant genes in races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) in wheat, exploration of new resistance genes in wheat relatives is necessary. Three accessions of Triticum cylindricum Ces. (4x, CCDD), Acy1, Acy9, and Acy11, were tested with 10 races each of leaf rust and stem rust. They were resistant to all races tested. Viable F1 plants were produced from the crosses of the T. cylindricum accessions as males with susceptible MP and Chinese Spring ph1b hexaploid wheats (T. aestivum, 6x, AABBDD), but not with susceptible Kubanka durum wheat (T. turgidum var. durum, 4x, AABB), even with embryo rescue. In these crosses the D genome of hexaploid wheat may play a critical role in eliminating the barriers for species isolation during hybrid seed development. The T. cylindricum rust resistance was expressed in the F1 hybrids with hexaploid wheat. However, only the cross MP/Acy1 was successfully backcrossed to another susceptible hexaploid wheat, LMPG-6. In the BC2F2 of the cross MP/Acy1//LMPG-6/3/MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 (infection types (IT) 1=, 1, or 1+; addition line 1) or stem rust race 15B-1 (IT 1 or 1+; addition line 2) were selected. Rust tests and examination of chromosome pairing of the F1 hybrids and the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. cylindricum C-genome chromosomes rather than on the D-genome chromosomes. The T. cylindricum chromosome in addition line 2 was determined to be chromosome 4C through the detection of RFLPs among the genomes using a set of homoeologous group-specific wheat cDNA probes. Addition line 1 was resistant to the 10 races of leaf rust and addition line 2 was resistant to the 10 races of stem rust, as was the T. cylindricum parent. The added C-genome chromosomes occasionally paired with hexaploid wheat chromosomes. Translocation lines with rust resistance (2n = 21 II) may be obtained in the self-pollinated progeny of the addition lines through spontaneous recombination of the C-genome chromosomes and wheat chromosomes. Such translocation lines with resistance against a wide spectrum of rust races should be potentially valuable in breeding wheat for rust resistance.     

Influence of Temperature on the Virulence of Two Races of Meloidogyne chitwoodi on Wheat and Barley

Races of the Columbia root-knot nematode, Meloidogyne chitzooodi, from Idaho (R1) and Utah (R2) suppressed (P < 0.05) tillering of Dusty winter wheat, Fielder spring wheat, Luther winter barley, and Steptoe spring barley at 15-30 C. Nematode inoculum density was negatively correlated with tillering (r = -0.79). Inoculum densities of both nematode races were negatively correlated with heads per plant (r = -0.83), head length (r = -0.87), and head dry weight (r = 0.73) of Fielder spring wheat and Steptoe spring barley at all temperatures; the greatest growth restrictions occurred at Pi 20 eggs/cm³ soil. Both nematode races were most damaging at 25-30 C. Fielder spring wheat and Steptoe spring barley inoculated with R2 produced fewer heads than R1 when inoculated at 15 C, whereas the same cultivars inoculated with R1 produced fewer heads than R2 at 30 C. No differences were observed between root growth of winter and spring wheat or between winter and spring barley. Nematode reproduction was positively correlated to temperature (r = 0.87) and negatively correlated with inoculum density (r = -0.86). Reproductive rates were greatest with Pi = 2 eggs/cm³ soil at 25 C and lowest with Pi = 20 eggs/cm³ soil at 15 C for both nematode races.     

Autotoxicity of wheat (Triticum aestivum L.) as determined by laboratory bioassays

Wheat varietal autotoxicity and varietal allelopathy were assessed based on plant extract and root exudate bioassays under laboratory conditions. Aqueous extract of wheat differed in varietal autotoxicity and varietal allelopathy, inhibiting wheat germination by 2–21%, radicle growth by 15–30%, and coleoptile growth by 5–20%, depending on the combination of the receiver and donor. Extracts of cv Triller or cv Currawong were more allelopathic to other wheat varieties than cv Batavia and cv Federation. Triller extract was more autotoxic than Federation. Assessment of root exudates by the equal-compartment-agar-method further identified the significant differences in varietal autotoxicity and varietal allelopathy of root exudates between wheat varieties, with root exudates of Triller or Batavia showing stronger autotoxic or allelopathic effects than Currawong or Federation. The varietal autotoxicity and allelopathy of root exudates also showed a characteristic radial inhibitory pattern in the agar growth medium. These results suggest that careful selection of suitable wheat varieties is necessary in a continuous cropping system in order to minimize the negative impacts of varietal allelopathy and varietal autotoxicity. Factors affecting autotoxicity in the field and strategies in autotoxicity management are discussed. Resposible Editor: Philippe Hinsinger     

春小麦品种对麦长管蚜生长发育和繁殖的影响

在室内25 ℃条件下研究了7种不同抗性的春小麦品种（系）对麦长管蚜生长发育和繁殖的影响.结果表明,不同抗性品种（系）对麦长管蚜若蚜发育历期、存活率、成蚜寿命和生殖力有显著的影响,麦长管蚜在抗性强的品种上成蚜寿命短、产仔量少;以内禀增长率作为测定抗生性的指标,供试小麦品种（系）对麦长管蚜抗生性的大小依次为辽春10号>02C-MB >新春6号>巴丰1号>永良4号>内麦19>蒙花1号,与田间抗性鉴定结果基本相同.