Inheritance and allelism of Russian wheat aphid resistance in several wheat lines

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) has caused serious reduction in wheat production in 17 Western states of the United States since 1986. Inheritance of resistance to RWA in seven wheat lines and the allelism of the resistance genes in these lines with three known resistance genes Dn4, Dn5, and Dn6 were studied. The seven resistant lines were crossed to a susceptible wheat cultivar ‘Carson’ and three resistant wheats: CORWA1 (Dn4), PI 294994 (Dn5), and PI 243781 (Dn6). Seedlings of the parents, F₁, and F₂ were screened for RWA resistance in the greenhouse by artificial infestation. Seedling reactions were evaluated 21–28 days after the infestation using a 1–9 scale. The resistance level of all the F₁ hybrids was similar to that of the resistant parent, indicating dominant gene control. Only two distinctive classes were present and no intermediate types were observed in the F₂ population, suggesting qualitative, nonadditive gene action, in which the presence of any one of the dominant alleles confers complete resistance to RWA. Resistance in CI 2401 is controlled by two dominant genes. Resistance in CI 6501 and PI 94365 is governed by one dominant gene. Resistance in PI 94355 and PI 151918 may be conditioned by either one dominant gene or one dominant and one recessive gene. No conclusion can be made on how many resistance genes are in AUSVA1-F₃, since the parent population was not a pure line. Allelic analyses showed that one of resistance genes in CI 2401 and PI 151918 was the same allele as Dn4, the resistance gene in CI 6501 was the same allele as Dn6, and AUS-VA1-F₃ had one resistance gene which was the same allele as one of the resistance genes in PI 294994. One non-allelic resistance gene different from the Dn4, Dn5, and Dn6 genes in CI 2401, PI 94355, PI 94365, and PI 222668 was identified and should be very useful in diversifying gene sources in wheat breeding.     

A Monosomic Analysis of Russian Wheat Aphid Resistance in the Common Wheat PI 294994

Chromosome 7D of PI 294994 was indicated as carrying a single dominant gene for resistance to the Russian wheat aphid. The symbol Dn5 is proposed to designate the gene.     

Inheritance of Russian wheat aphid resistance in PI 140207 spring wheat

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a serious, perennial pest of wheat (Triticum aestivum L.) in many areas of the world. This study was initiated to determine the inheritance of RWA resistance in PI 140207 (a RWA-resistant spring wheat) and to determine its allelic relationship with a previously reported RWA resistance gene. Crosses were made between PI 140207 and ‘Pavon’ (a RWA-susceptible spring wheat). Genetic analysis was performed on the parents, F₁, F₂, backcross (BC) population and F₂-derived F₃ families. Analyses of segregation patterns of plants in the F₁, F₂, and BC populations, and F₂-derived F₃ families indicated single dominant gene control of RWA resistance in PI 140207. Results of the allelism test indicated that the resistance gene in PI 140207, while conferring distinctly different seedling reactions to RWA feeding, is the same as Dn 1, the resistance gene in PI 137739.     

Effect of the Russian Wheat Aphid on the Composition and Synthesis of Water Soluble Proteins in Resistant and Susceptible Wheat

The effect of Russian wheat aphid ( Diuraphis noxia) infestation on polypeptide composition and protein synthesis in the presence or absence of chloramphenicol and cycloheximide were studied in genetically comparable wheat ( Triticum aestvum) resistant (cv. PI 137739/5* Tugela) and susceptible (cv. Tugela) to the aphid. The aim is to gain information of molecular nature on the resistance phenomenon which may promote future breeding programmes. In the absence of feeding aphids polypeptide profiles of the two wheat lines were similar indicating the absence or presence at low levels of a constitutive resistance factor. Aphid infestation induced enhanced expression of certain genes in the resistant wheat only. A 100 kD nuclear encoded polypeptide is strongly induced in the resistant wheat. It is also evident that the synthesis of a 56 kD organel encoded polypeptide is suppressed by the feeding aphids in the susceptible wheat.     

Inheritance and allelism of resistances to the Russian wheat aphid in seven wheat lines

Summary Studies were conducted to determine the inheritance and allelic relationships of genes controlling resistance to the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), in seven wheat germplasm lines previously identified as resistant to RWA. The seven resistant lines were crossed to a susceptible wheat cultivar Carson, and three resistant wheats, CORWA1, PI294994 and PI243781, lines carrying the resistance genes Dn4, Dn5 and Dn6, respectively. Seedlings of the parents, F₁ and F₂ were screened for RWA resistance in the greenhouse by artificial infestation. Seedling reactions were evaluated 21 to 28 days after the infestation using a 1 to 9 scale. All the F₁ hybrids had equal or near equal levels of resistance to the resistant parent indicating dominant gene control. Only two distinctive classes were present and no intermediate types were observed in the F₂ segregation suggesting major gene actions. The resistance in PI225262 was controlled by two dominant genes. Resistance in all other lines was controlled by a single dominant gene. KS92WGRC24 appeared to have the same resistance gene as PI243781 and STARS-9302W-sib had a common allele with PI294994. The other lines had genes different from the three known genes.     

Inheritance and allelic relationships of resistances to the Russian wheat aphid in two Iranian wheat lines

Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a serious pest of small grains in many countries. A previous study screened 70 genotypes, collected from different parts of Iran, for RWA resistance. Four crosses were made between two resistant lines (Shz.W-102 and Shz.W-104) and two susceptible lines (Shz.W-101 and Shz.W-103). Parents, F₁, F₂, and BCF₁ seedlings were screened for RWA resistance in the greenhouse by artificial infection. To determine allelism, the two resistant lines were intercrossed and F₁, and F₂ seedlings were evaluated. Resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-101, was controlled by one dominant gene. However, resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-103, was controlled by two dominant genes. Genes in two resistant lines segregated independently of each other. A three-gene system was proposed to govern resistance in the lines under study . This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of resistance to the Russian wheat aphid in an Iranian durum wheat line

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a major economic pest of small grains in many countries. An experiment was therefore conducted to determine the inheritance of gene(s) controlling resistance to RWA in a resistant tetraploid durum wheat line. This resistant line,‘1881′, was crossed to a susceptible line, ‘Orejy‐e‐Kazeroon’, and then F₁ F₂ and BCF₁ (backcross to susceptible line) seedlings were screened in a greenhouse for RWA resistance following artificial infection. Resistance in ‘1881’ was apparently controlled by one dominant gene. Since Dnl, Dn2, dn3, Dn4 and Dn5 have been reported to be located on genome D, it was reasoned that the resistance gene in ‘1881’ is not allelic to them.     

Host plant resistance in some wild wheats to the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae)

A total of 259 accessions of wild Triticum species originating from different countries, along with 91 triticale (6×)× bread wheat true-breeding derivatives, two bread wheat, and three triticale cultivars were screened for resistance to the Russian wheat aphid, a serious insect pest of the wheat crop. Twenty-four entries with low damage ratings on the basis of amount of leaf rolling and leaf chlorosis were retested along with resistant and susceptible controls. On the basis of leaf roll damage ratings, eight entries including four Triticum monococcum var. boeoticum (T. boeoticum), one T. monococcum var. monococcum (T. monococcum), two T. timopheevii var. araraticum (T. araraticum), and one triticale cultivar were significantly superior to ‘Karl’ (susceptible control) wheat. Among these, four accessions — three T. boeoticum and one T. araraticum— were significantly superior to all other entries and were equal to the resistant control (PI 372129) in resistance rating based on leaf rolling and leaf chlorosis (except T. boeoticum TA 202). The leaf chlorosis damage rating of all accessions were significantly lower than that of the susceptible check.     

Detection of Resistance to the Russian Wheat Aphid in Hexaploid Wheat

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), poses a serious threat to wheat (Triticum aestivum L.) production in many parts of the world. This research was initiated to evaluate wheat accessions for detection of resistance to the RWA. Over 12,000 wheat cultivars and plant introductions (PIs) from the USDA-ARS National Small Grains Collection were evaluated for reaction to RWA feeding damage. Twenty-nine PIs from Iran, Afghanistan, and the former Soviet Union, of various agronomic backgrounds were identified as having moderate to high levels of RWA resistance. This information is useful to wheat breeders searching for sources of resistance to the RWA to incorporate into their breeding programmes.     

The Transfer of Resistance to the Russian Wheat Aphid from Triticum monococcum L. to Common Wheat

Two Triticum monococcum accessions were found to be highly resistant to the Russian wheat aphid. An attempt was made to transfer the resistance to common wheat through direct hybridization or by using bridge species. In each of the four crossing strategies tried, a gradual loss of resistance occurred as hybrids with higher ploidy levels were obtained. It appeared that the level of resistance observed was directly proportional to the ratio of the Triticum monococcum genome relative to other genomes. This would indicate suppression of the resistance gene(s) by the added genomes or dilution of its product(s) by those of homoeoloci. The degree of protection afforded by the gene(s) at the hexaploid level may prove to be small. Plants suspected to be homozygous for the resistance gene(s) were identified; however, further backcrossing to common wheat will be required to improve their agronomic types and meiotic regularities.     

Inheritance of resistance to Russian wheat aphid in barley

Summary The inheritance of resistance to Russian wheat aphid Diuraphis noxia (Mordvilko), in two resistant barleys, Hordeum vulgare L., ASE/2CM//B76BB and Gloria/Come, was studied in the field and in the greenhouse. The resistant genotypes were crossed with susceptible genotypes Esperanza and Shyri. Resistance reactions of F1, BC1, and F2 plants, and individual F2 plant derived F3 families indicated that resistance in each genotype was controlled by the same single dominant gene.     

Intergeneric Transfer (Rye to Wheat) of a Gene(s) for Russian Wheat Aphid Resistance

An octoploid triticale was derived from the F, of a Russian wheat aphid-resistant rye, ‘Turkey 77’, and ‘Chinese Spring’ wheat. The alloploid was crossed to common wheat, and to ‘Imperial’ rye/‘Chinese Spring’ disomic addition lines. F₂, progeny from these crosses were tested for Russian wheat aphid resistance and C-banded. A resistance gene(s) was found to be associated with chromosome arm IRS of the ‘Turkey 77’ rye genome. A monotelosomic IRS (‘Turkey 77’) addition plant was then crossed with the wheat cultivar ‘Gamtoos’, which has the 1BL.1RS ‘Veery’ translocation. Unlike the IRS segment in ‘Gamtoos’, the ‘Turkey 77’-derived 1 RS telosome did not express the rust resistance genes Sr31 and Ar26, which could then be used as markers. From the F, a monotelosomic 1 RS addition plant that was also heterozygous for the 1BL. 1 RS translocation was selected and testerossed with an aphid-susceptible common wheat, ‘Inia 66’ Meiotic pairing between the rye arms resulted in the recovery of five euploid Russian-wheat-aphid-resistant plants. One recombinant also retained Sr31 and Lr26 and was selfed to produce translocation homozygotes.     

DNA and morphological markers for a Russian wheat aphid resistance gene

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a significant insect pest of wheat worldwide. Morphological and molecular markers associated with RWA resistance could be used to increase the accuracy and efficiency of selection of resistant germplasm and facilitate transfer to desirable wheat genotypes. The objective of this work was to identify microsatellite (SSR) markers linked to the RWA resistance gene (Dn4) and glume-colour gene (Rg2) using a population of F₂-derived F₃ families originating from a cross between a susceptible line (synthetic hexaploid-11) and a resistance cultivar (Halt). Two microsatellite markers Xgwm106 and Xgwm337 flanked Dn4 on the short arm of chromosome 1D at 5.9 and 9.2 cM, respectively. Two other microsatellite markers, Xpsp2999 and Xpsp3000, at the distal part of this chromosome arm are linked to Dn4 and to Rg2. The accuracy and efficiency of marker-assisted selection were calculated for homozygous Dn4Dn4 genotypes in the F₂ generation. The gene Rg2 for red glume colour can also be used for marker-assisted selection of Dn4 gene individually and in combination with microsatellite markers. When used together, the closest markers Xgwm106 and Xgwm337, provide 100% accuracy and 75% efficiency. One hundred percent accuracy is also achieved when the morphological marker red glume is used in combination with either Xgwm106 or Xgwm337. Using these flanking markers, it may be possible to fix resistance to RWA in the first segregating generation of an F₂ population without infestation with aphids.     

Evidence of allelism between genes Pm8 and Pm17 and chromosomal location of powdery mildew and leaf rust resistance genes in the common wheat cultivar'Amigo'

TIBL-1RS wheat-rye translocation cultivars utilized in wheat programmes worldwide carry powdery mildew resistance gene Pm8. Cultivar‘Amigo’possesses resistance gene Pm17 on its TIAL-1RS translocated chromosome. To be able to use Pm17efficiently in breeding programmes, this gene was transferred to a TIBL-1RS translocation in line Helami-105, and allelism between Pm8 and Pm17was studied. The progenies of the hybrids in the F₂ generation and F₃ families provided evidence that the two genes are allelic. Genetic studies using monosomic analyses confirmed that in cultivar‘Amigo', Pm17 and leaf rust resistance gene Lr24 are located on a translocated chromosome involving 1 A and 1B, respectively.     

Different types of resistance against greenbug, Schizaphis graminum Rond, and the Russian wheat aphid, Diuraphis noxia Mordvilko, in wheat

A collection of 26 cultivars of wheat Triticum aestivum were screened for resistance against the two main aphid pests of cereals, the greenbug Schizaphis graminum Rond. and the Russian wheat aphid (RWA) Diuraphis noxia Mordvilko. Since genetic variability has been found in Argentinean populations of both aphid species, this work was aimed at determining the response of different types of resistance in wheat cultivars when infested with aphids. Antixenosis, antibiosis and tolerance were evaluated with traditional tests in controlled environmental conditions using a clone of greenbug biotype C and a clone of RWA collected on wheat. Genetic resistance was found against one or both aphid species in several wheats. Most of the highest levels of antixenosis, antibiosis and tolerance against the two aphids occurred in different cultivars; as a consequence the resistance mechanisms for both pests appear to be partly independent. Antibiosis against greenbug or RWA appears to be determined by two different sets of genes, one affecting development time and the other reducing fecundity and longevity. The antibiosis against both aphid species in terms of their development time and the intrinsic rate of population increase resulted in a partial cross effect of these aphid traits against the alternative insect species. Nonetheless, the same cultivars affected the total fertility and the longevity of both aphids. Since the highest plant performance levels and the least plant damage were recorded in different wheats, different patterns of tolerance were displayed against the greenbug and the RWA. Consequently, different genes appear to be involved in several traits of the resistance mechanisms against the two aphids. The genes that independently conferred resistance to aphids could be combined in new cultivars of wheat to broaden their genetic base of resistance against the greenbug and the RWA.     

Mapping quantitative trait loci in wheat for resistance against greenbug and Russian wheat aphid

Breeding for genetic resistance against greenbug and Russian wheat aphid (RWA) is the most effective way of controlling these widespread pests in wheat. Earlier work had shown that chromosome 7D of a synthetic hexaploid wheat, ‘Synthetic’ (T. dicoccoides × Ae. squarrosa) (AABB × DD) gave resistance when transferred into the genetic background of an aphid‐susceptible cultivar, ‘Chinese Spring’, as the recipient. To map the genes involved, a set of 103 doubled haploid recombinant substitution lines was obtained from crossing the 7D substitution line with the recipient, and used to determine the number and chromosomal location of quantitative trait loci (QTL) controlling antixenosis and antibiosis types of resistance. Antixenosis to RWA was significantly associated with marker loci Xpsr687 on 7DS, and Xgwm437 on 7DL. Antibiosis to greenbug was associated with marker loci Xpsr490, Rc3 (on 7DS), Xgwm44, Xgwm111, Xgwm437, Xgwm121 and D67 (on 7DL). Similarly, antibiosis to RWA was linked to loci Xpsr490, Rc3, Xgwm44, Xgwm437 and Xgwm121. At least two QTL in repulsion phase, one close to the centromere either on the 7DS or 7DL arms, and a second distal on 7DL could explain antibiosis to RWA and, partially, this mechanism against greenbug.     

A Dynamic Model for Water and Nitrogen Limited Growth in Spring Wheat to Predict Yield and Quality

Annual variation of bread wheat ( Triticum aestivum L.) yield and quality has caused problems for agronomic policy in northern regions. Yield prediction methods based on visual assessment of crop may be inaccurate as they are not based on quantitative data. The aim of this study was to develop a simple dynamic model, based on daily climatological data, enabling prediction of crop growth, and changes in crop yield, and grain protein concentration and starch quality. The model was built using field data collected in 1972–88. Spring wheat cultivars included in the study were Kadett and Ruso. The calibration of growth and Hagberg falling number (used as a measure of starch quality) sub-models resulted in a highly significant positive correlation between measured and calculated values. The calibration of nitrogen sub-models failed, however, with poor correlation between measured and calculated values. The model was tested against independent field data collected during 1989–90, and results correlated with calibration results. The yield predictions based on independent field data were accurate, and the same as or similar to field trial results. However, the independent Hata revealed flaws in soil-water and Hagberg falling number sub-models.     

Genes for Powdery Mildew Resistance in Cultivars of Spring Wheat

Twenty-three cultivars of spring wheat were inoculated with nineteen different powdery mildew isolates; their ruction patterns hive been compared with those of twenty-two cultivars/lines carrying identified powdery mildew resistance genes. Applying the gene-for-gene hypothesis, it is evident that three cultivars have none of the resistance genes used, seven others (including ‘Solo’) may carry Pm4b, only. The resistance pattern of ‘Selpek’ is identical to A/-1 resistant cultivars of winter wheat and may be explained by the presence of Pm5. The resistance pattern of Pm5 (Mt-i) cultivars is very different from a number of ‘Kolibri’-related cultivars of spring wheat. Since either all or nothing of that specific pattern has been transferred to all cross progenies of ‘Kolibri’, a single gene is assumed to oe responsible for it, preliminarily designated as Ml-k. The cultivar ‘Mephisto’ carries the ‘Normandie’ resistance (Pwl 2, 9). In five cultivars to spring wheat the combined effects of at least two of the above-mentioned sources have been found. Despite the fact that ‘Normandie’ and ‘Sappo’ are not closely related. ‘Sappo’ shows the complete ‘Normandie’ resistance pattern plus that of Pm4b. The same is true for ‘Planet’ and ‘Walter’.     

Genetic control of Russian wheat aphid (Diuraphis noxia) resistance in wheat accession PI 47545

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a major pest of cereal crops in many areas of the world, causing serious reduction in grain yield in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Incorporating genetic resistance to D. noxia into wheat cultivars is paramount to effectively reduce damage inflicted by this pest. Genetic resistance to D. noxia has been identified in wheat, barley and rye germplasm, and several resistance genes are available for use for cultivar improvement. In the United States of America, only a few Russian wheat aphid (RWA) resistant winter wheat cultivars are currently available, and these cultivars contain only one of the six known RWA resistance genes. The objective of this study was to determine the inheritance of RWA resistance in wheat accession PI 47545, using a screening method based on differences in the leaf morphology of resistant and susceptible types following insect challenge. PI 47545 was selected for study, since it displayed high levels of resistance in a white-grained wheat background, the predominant wheat class produced in the Pacific Northwest of the USA. Segregation analysis was conducted on an F₂ population developed by cross-hybridizing the susceptible soft white winter wheat cultivar ‘Daws’ to the resistant accession PI 47545. Russian wheat aphid screening data from this population indicated that the resistance in PI 47545 is controlled by a single, dominant gene (χ² = 1.72; p ≤ 0.189). This revised version was published online in August 2006 with corrections to the Cover Date.     

Inheritance of resistance to Tilletia indica (Mitra) in synthetic hexaploid wheat ×Triticum aestivum crosses

Inheritance of resistance to Karnal bunt was investigated in the crosses of four resistant synthetic hexaploid wheats (SH; Triticum turgidum×T. tauschii) and two susceptible T. aestivum cultivars. The resistance was dominant or partly dominant over susceptibility. The SH cultivars Chen/T. tauschii (205) and Chen/T. tauschii (224) have single dominant resistance genes which could be allelic to each other. ‘Altar 84’/T. tauschii (219) appeared to have two dominant genes for resistance. ‘Duergand’T. tauschii (214) possessed two complementary dominant genes for resistance. The work is being extended to involve diverse Karnal bunt-resistant SH and bread wheat cultivars.