Wheat streak mosaic virus resistance in eight wheat germplasm lines

Wheat streak mosaic virus (WSMV) is a destructive pathogen in wheat (Triticum aestivum L.). Host resistance is the most effective way to control this virus. To date, Wsm2 is the only wheat resistance gene that is genetically mapped. The objective of this study was to identify germplasm lines that might carry resistance genes different from Wsm2. Eight newly reported resistant germplasm lines were examined by allelic tests. To validate the allelic test results, five of them were further analysed for the inheritance of WSMV resistance. A Wsm2‐linked marker was also genotyped on populations developed for the inheritance study. Our results suggested that the WSMV resistance in lines CItr9358, PI225288, PI243652, PI245439, PI245526 and PI478095 was controlled by either Wsm2 or a gene very closely linked to Wsm2. The resistance in PI243753 and PI321730, however, is likely controlled by a gene different from, but linked to Wsm2. The resistance in PI321730 might also involve some minor genes. This study provided useful information for breeders to select appropriate resistant lines to improve WSMV resistance in wheat.     

Inheritance and allelism of wheat streak mosaic virus resistance in two Iranian wheat lines

Wheat streak mosaic (WSM) caused by wheat streak mosaic virus (WSMV) is a serious disease of wheat and many plants in the grass family. In previous studies genotypes collected from different parts of Iran, were screened for WSM resistance. Two resistant genotypes, “Adl Cross” and “4004” were crossed to one susceptible genotype “Marvdasht.” Reciprocal crosses were also made. Seedlings of parents, F₁, F₂, backcrosses to susceptible (BCS) and resistant (BCR) were evaluated for WSMV reaction based on scales 0–7, by artificial infection under greenhouse conditions. Allelism was studied by evaluating the F₁ and F₂ seedlings of the resistant × resistant cross. Inheritance of resistance to WSMV in Adl Cross and 4004 was controlled by one dominant gene. No allelism was observed between resistance genes. Among the F₂ seedlings of the resistant × resistant cross relatively more resistant genotypes with a zero score were observed. These two genes, therefore, can be incorporated into an adapted wheat cultivar to produce a more durable resistance.     

Agronomic and quality effects in winter wheat of a gene conditioning resistance to wheat streak mosaic virus

Wheat streak mosaic virus (WSMV) is one of the most important diseases limiting winter wheat (Triticum aestivum L.) production in the western Great Plains of North America. There is no known effective WSMV resistance within the primary gene pool of wheat. However, a resistance gene (Wsm1) has been transferred to wheat from a perennial relative, intermediate wheat-grass [Thinopyrum intermedium (Host) Barkworth & DR Dewey]. Nebraska-adapted winter wheat lines carrying Wsm1 were used to characterize the effects of this alien introgression on agronomic and quality traits. Sister-lines from six breeding populations were evaluated under virus-free conditions, and under a naturally occurring viral infection. In uninfected locations, no significant difference for grain yield was detected between resistant (R) and susceptible (S) lines, when averaged over populations, but resistant lines had significantly higher test weights. Within populations, significantly higher grain yield was observed only in population 1, while significantly higher test weights occurred in populations 1, 2, 5 and 6. At the infected location, resistant lines were significantly higher in yield in five of six populations. In two of six populations, susceptible lines were significantly higher in bread loaf volume and bake mix time, while in the remaining populations, no significant quality differences were observed. As the Wsm1 gene provided yield advantages under viral infection, and there was no yield detriment in the absence of the virus, its deployment in hard winter wheat cultivars merits consideration.Joint contribution of the United States Department of Agriculture, Agricultural Research Service and the Department of Agronomy, University of Nebraska-Lincoln as Journal Series Paper No. 15066. Mention of firm names or trade products does not imply that they are endorsed or recommended by the USDA or the University of Nebraska over other firms or products not mentioned.     

Resistance in tomato to tobacco mosaic virus

The literature on resistance in tomato to TMV is reviewed. The chronological sequence of publication and the relationships between the material of different workers is show graphically. The sources of resistance and the genotype/environment interaction is discussed. The author asks for an increased standardisation of techniques, greater attention to tests for allelism and a responsible attitude when resistant varieties are to be released.There are 54 references     

Inheritance of biotype E greenbug resistance in bread wheat CI 17882 and its relationship with wheat streak mosaic virus resistance

Summary Genetic studies were conducted to determine the inheritance of biotype E greenbug resistance in CI 17882 (CI 15092/T. speltoides//Fletcher/3/4^* Centurk), a wheat germplasm line previously released as resistant to wheat streak mosaic virus (WSMV). In addition, the association of greenbug and WSMV resistance in CI 17882 was examined. Results indicated that biotype E greenbug resistance in CI 17882 is conditioned by a single dominant gene that is not linked with the WSMV resistance gene.Cooperative research of the USDA, Agricultural Research Service and the Oklahoma Agricultural Experiment Station. Journal article 4845 of the Oklahoma Agric. Exp. Stn., Oklahoma State Univ., Stillwater, OK 74078.     

Resistance to turnip mosaic virus in white cabbage

Summary Resistance in white cabbage to external necrosis caused by turnip mosaic virus had a significant genetic component. Estimates of heritability ranged from 41% to 48%. Resistance to internal necrosis was determined by unknown environmental factors with no significant genetical component. Although correlation between external and internal symptoms was poor in general, plants which had no external symptoms at harvest did not develop internal symptoms during storage. It is proposed that selection for lack of external symptoms will also produce lines resistant to internal symptoms.     

Resistance to tobacco mosaic virus in lycopersicon hybrids evaluated by potato virus x synergy

A method employing simultaneous inoculation with TMV (tobacco mosaic virus) and PVX (potato virus x) was compared with the conventional TMV inoculation in tests with known susceptible, resistant and segregating lines and varieties of tomato seedlings. While inoculation with TMV alone caused 63 to 88 percent systemic symptoms in known susceptible seedlings, the double virus method resulted in 100 percent necrotic streak and stunt. In advanced resistant lines such symptoms were entirely absent and when tested in the field against heavy TMV infection were found to be highly resistant. Thus, it appears that resistance to TMV in these derivatives of Lycopersicon hybrids can be decisively evaluated by the double virus inoculation method.Associate Professor of Plant Pathology, Department of Botany and Plant Pathology, Michigan State University. East Lansing, Michigan.Associate Professor of Horticulture, Department of Horticulture, Michigan State University. Journal Article No. 3100, Michigan Agricultural Experiment Station.     

Marker-assisted identification of resistance genes to soybean mosaic virus in soybean lines

Soybean plants react differentially to soybean mosaic virus (SMV) strains because of interactions among different resistant genes in the soybean genome. Three independent genes resistant to SMV have been identified by inheritance studies and linkage analyses. To develop durable SMV-resistant soybean cultivars, it is necessary to determine which soybean SMV resistance genes can be readily transferred from resistant to susceptible cultivars in a breeding system. Here, we report the type and number of resistance gene(s) in four Korean elite soybean cultivars using a combination of disease reaction symptoms, inheritance studies, and molecular marker mappings. The disease reactions of Sowonkong and Keunolkong soybean varietals in response to infection with SMV strains suggested that both cultivars most likely harbor the Rsv1 gene similar to that in York. Subsequent inheritance studies confirmed that Sowonkong has the Rsv1 gene. The inheritance studies suggested that Sinpaldalkong harbored the Rsv1 gene, which was then confirmed by molecular marker mapping. The inheritance studies also suggested that Jinpumkong 2, which is the most resistant to SMV infection among the four cultivars, contained the Rsv1 and Rsv3 genes; this was confirmed by molecular marker mapping. Our approach, which combined inheritance studies and molecular linkage analyses, allowed the efficient identification of resistance gene(s) in four Korean soybean cultivars.     

Resistance of Cucurbita moschata to watermelon mosaic virus type 2 and its genetic relation to resistance to zucchini yellow mosaic virus

Summary Cucurbita moschata Menina originating from Portugal is known to carry a single dominant gene, Zym, for zucchini yellow mosaic virus (ZYMV) resistance. Resistance to watermelon mosaic virus type 2 (WMV2) was found in the same cultivar. In resistant plants, WMV2 migration from inoculated leaves or cotyledons seems to be limited and blocked. Resistance to WMV2 is conferred by one dominant gene and is effective against eight strains from different geographic origins. Results of linkage studies, based on co-inoculation of plants with WMV2 and ZYMV, indicate that resistance to these two viruses is conferred by the same gene, probably Zym, or perhaps by two closely linked genes.     

Breeding maize lines for complete and partial resistance to maize streak virus (MSV)

Summary S₁ to S₅ inbred lines, derived from a maize population bred for its overall resistance to three tropical viruses, were screened for resistance to maize streak virus (MSV) by artificial plant infection using viruliferous leafhoppers. Symptoms were rated and intra-line frequency distributions studied for all pedigree inbred lines. Mortality due to MSV was very low among these inbreds. Symptoms appeared later, developed slower and were less severe than in the susceptible control hybrid. Results of a study of 500 S₁ and 93 S₂ lines suggested that resistance is under genetic control via a system involving loci with major genes (with dominance for resistance) controlling high to complete resistance, associated with a genetic system involving loci with minor genes controlling partial resistance. Lines expressing complete resistance to MSV were developed from 5 cycles of inbreeding and selection. The relevance of such complete and partial resistance is discussed.Abbreviations MRPS Mean Rating for Plants exhibiting Symptoms     

Resistance at the TM-2 locus in the tomato to tomato mosaic virus

Summary There are three known tomato mosaic virus (TMV) resistance factors, Tm-1, Tm-2 and Tm-2 ², in the tomato. Tm-2 ² is currently the most widely utilised in glasshouse cultivars. Both Tm-2 and Tm-2² can induce systemic necroses in response to virus infection. These are considered to be hypersensitive resistance reactions in view of the low virus concentrations in affected plants and because sub-inoculation usually fails to infect all plants possessing the same resistance gene. The literature relating to TMV resistance at the Tm-2 locus in the tomato is reviewed.Virulent strains may readily establish when Tm-1 or Tm-2 are used, but Tm-2 ² confers more effective resistance. The possible development of aggressive isolates capable of affecting Tm-2 ²/Tm-2² plants is discussed. The establishment of virus types which cause systemic necrosis at normal growing temperatures is considered more likely than widespread infection from fully virulent strain 2² mutants. However, the growing of crops isolated from the TMV reservoirs in the soil considerably reduces the likelihood of even this occurring.     

Resistance of early-maturing European maize germplasm to sugarcane mosaic virus (SCMV) and maize dwarf mosaic virus (MDMV)

Sugarcane mosaic virus (SCMV) and maize dwarf mosaic virus (MDMV) are the most important viruses of maize in Europe. In field and greenhouse experiments, 122 early-maturing European maize inbreds (45 flint and 77 dent lines) were evaluated for their reaction to artificial inoculation by SCMV and MDMV. Three dent inbreds (D21, D32, FAP1360 A) with complete resistance and four dent inbreds (D06, D09, R2306, FAP1396A) with partial resistance against both potyviruses under both greenhouse and field conditions were identified. All other inbreds were highly susceptible to both SCMV and MDMV. Selection for virus resistance in maize breeding could be performed with only one virus at a time because all inbreds resistant to SCMV were also resistant to MDMV. Rank correlations between percentages of infected plants in greenhouse and field trials ranged from 0.51 to 0.72 for both SCMV and MDMV, suggesting that prescreening of breeding materials for virus resistance can be performed in the greenhouse but final evaluation in multilocation trials in the field is recommended.     

高抗烟草花叶病毒的烟草种质资源筛选

为了解我国烟草种质资源对烟草花叶病毒(Tobacco mosaic virus,TMV)的抗性状况,为烟草抗病育种的亲本选择提供信息,本试验通过苗期TMV汁液摩擦接种,对1 191份烟草种质资源进行了TMV抗性鉴定.筛选出的对TMV表现为枯斑反应的高抗资源有:白肋烟40份、国内烤烟20份、国外烤烟28份、晒烟1份,合计89份.接种后21 d表现为花叶的资源有:白肋烟29份、国内烤烟430份、国外烤烟270份、国内晒烟352份、国外晒烟(雪茄烟)21份,合计1 102份.枯斑资源的比例白肋烟＞烤烟＞晒烟.云南省烟草农业科学研究院2006年保存白肋烟、烤烟和晒烟资源合计1 652份,本试验较系统的鉴定了72％种质资源的TMV抗性状况,可为种质资源的育种利用提供参考.     

大豆新品系抗SMV鉴定及分析

为了筛选出对大豆花叶病毒(SMV)病具有抗性的大豆新品系,以1108份新选育的大豆品系为材料,人工接种SMV优势株系SC3和SC7,通过调查发病率和病情指数以考察其抗性,同时分析其亲本来源和抗性.结果显示,有356和326份大豆品系对SMV株系SC3和SC7分别表现高抗,占比为32.13％,29.42％,同时对这2个株系均表现高抗的品系有252份,占22.75％.相关性分析结果显示,SC3和SC7发病率与病情指数呈极显著正相关(r=0.942和r=0.956).线性回归结果显示,SC3和SC7发病率与其病情指数呈线性关系,线性关系显著,其发病率可以分别解释其病情指数变异的88.75％,91.47％.从亲本来源可以看到,母本来源于河北育成的品系数最多,有97份;父本来源于国外育成的品系数最多,为85份.抗性分析显示,来源于河北的母本抗性的病情指数相对较低,其后代品系平均发病率和病指指数也均相对较低.研究结果为SMV病情预测和大豆抗病育种提供了参考.     

小麦近缘属种纹枯病的抗性鉴定

用土壤接种法对２６份小麦近缘材料、栽培品种及其杂交后代的抗纹枯病性能进行了鉴定。结果表明,小麦近缘植物中存在着丰富的抗纹枯病资源,其中有５份材料表现免疫,他们是节节麦３４、峨观草、野燕麦、八倍体小黑麦、六倍体小黑麦;有１２份材料表现高抗,他们是斯卑尔脱小麦、峨观草（河南）、圆锥小麦、密穗小麦、二棱大麦、阿比西尼亚小麦、节节麦３４×Ｂ１８６、波兰小麦、六棱大麦、硬粒小麦、四棱小麦、茹可夫斯基小麦;有５份材料表现中抗,他们是波斯小麦、东方小麦、节节麦２８×冀麦５４１８、印度圆粒小麦、节节麦２８;只有节节麦３４×豫麦９号为高度感病。     

Resistance in spelt wheat to yellow rust

Summary Seven spelt wheat accessions of different origin were hybridized with the susceptible bread wheat cultivar Taichung 29 in order to study the genetics of their resistance to yellow rust (Puccinia striiformis Westend. f. sp. tritici). One Iranian and five European accessions were found to carry Yr5 of Triticum aestivum ssp. spelta var. album, whereas a factor for resistance in the Iranian accession 415 was confirmed to be genetically distinct from Yr5. The alleles for resistance in each of the accessions studied showed a monogenic dominant mode of inheritance. Twenty-eight spelt wheat accessions, including those studied for their resistance to yellow rust, were subjected to polyacrylamide-gel-electrophoresis to study variation for gliadin storage protein patterns. Thirteen distinct patterns were revealed, implying the presence of duplicates within the studied spelt wheat collection.     

Genetic control of resistance to soilborne wheat mosaic virus in Brazilian cultivars of Triticum aestivum L. Thell.

In Southern Brazil, under ideal conditions Soilborne Wheat Mosaic Virus (SBWMV) induces yield reductions to the wheat crop of over 50%. The only effective way of controlling the disease is through resistance. However, the inheritance of resistance is not been fully understood. The purpose of this work was to study the genetic control of resistance to SBWMV. Crosses were carried out between the resistant wheat cultivar Embrapa 16 and the susceptible cultivars BR 23 and IAC 5-Maringá, at the National Wheat Research Centre, Passo Fundo, RS, Brazil. The parents, F₁, F₂, and backcrosses were sown in plots in a field where soil was naturally infested with the vector of the virus, the fungus Polymyxa graminis, in order to promote natural infection. All plants were individually evaluated for severity and type of lesions, according to a scale of 0 to 5, where, 0 = absence of symptoms and 5 = plants severely affected by mosaic plus dwarfing and rosetting. The statistical analyses of the data showed broad sense heritability values between 43% and 55%. The data suggested the presence of two genes controlling resistance to SBWMV in the segregating population of both crosses. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Generation means analysis of <Emphasis Type="Italic">wheat streak mosaic</Emphasis> virus resistance in winter wheat

Wheat streak mosaic virus (WSMV; Family: potyviridae; Genus: Tritimovirus) is a major threat to winter wheat (Triticum aestivum L. em. Thell) production worldwide, yet little is known about the genetic control of resistance. Our objective was to determine the mode of inheritance and type of gene action of WSMV resistance in two winter wheat crosses involving a resistant line, OK65C93-8, and two susceptible cultivars, Tandem and Vista. For each cross, parents, F₁, F₂, and backcross plants were inoculated and evaluated for WSMV resistance in two replicated greenhouse experiments. Generation means analysis indicated that additive, dominance, and epistatic effects were all involved in the inheritance of WSMV resistance. Broad-sense heritability estimates for visual symptom rating and ELISA values were high for both crosses (0.84–0.91). Narrow-sense heritability estimates were low in the Tandem/OK65C93-8 cross (0.43–0.45) and moderate in the Vista/OK65C93-8 cross (0.71–0.74). Due to the presence of greater non-additive gene effects combined with low narrow-sense heritability in the Tandem/OK65C93-8 cross, selecting for WSMV resistance in this cross would be complex if using conventional methods. On the other hand, the significant contribution of additive gene effects combined with moderate narrow-sense heritability in the Vista/OK65C93-8 cross suggested that it could be exploited to select for WSMV resistance. Progress from selection for WSMV resistance in early generations of winter wheat may vary among populations as indicated in this study. Therefore, evaluating genetic control of parental combinations may be warranted prior to selecting for WSMV resistance from this source.     

Characterization of the Q.Ymym region on wheat chromosome 2D associated with wheat yellow mosaic virus resistance

Yellow mosaic disease, caused by wheat yellow mosaic virus (WYMV), is one of the most serious diseases of winter wheat in Japan and China. A single major QTL for WYMV resistance in the Japanese wheat variety 'Yumechikara', designated Q.Ymym, has been mapped on a 43.6 cM linkage block between the two markers Xcfd233 and Xgwm349 on chromosome 2D. We were able to obtain two recombinants within the block, which facilitated reducing the size of the linkage block. The pseudomolecule sequence of 'Chinese Spring' (CS) indicated that the original Q.Ymym region of 43.6 cM corresponded to 68.5 Mb and the narrowed Q.Ymym region represents a size of 27.3 Mb. The sequence features of the Q.Ymym region were unique in comparison with CS sequences, which may have led to the low recombination rate within the block. The Q.Ymym haplotype block was detected in other WYMV-resistant varieties but not in the susceptible varieties used in this study. The unique sequence structure of the Q.Ymym region allowed the development of co-dominant markers for use in marker-assisted selection.