Posts Tagged ‘resistance’

Effectiveness of three potential sources of resistance in wheat against Wheat streak mosaic virus under field conditions

Posted by Carelia Juarez on , in Journal Articles

Published in Australasian Plant Pathology 41 (3) : 301-309, 2012

Muhammad Fahim, Philip J. Larkin, Steve Haber, Steve Shorter, Paul F. Lonergan and Garry M. Rosewarne

Wheat streak mosaic virus is an established major threat to wheat in North America and is newly identified in Australia. Three genetic sources of resistance were examined, Wsm1 (from an alien translocation), Wsm2 (from CO960293-2), and c2652 (selected in Canada). We report their effectiveness in the field when inoculated with an Australian WSMV isolate. Also included were advanced breeding lines with and without Wsm2 and a number of elite Australian cultivars. ELISA testing on individual plants indicated we achieved between 85% and 100% infection with WSMV in susceptible lines following artificial inoculation which reduced their yield by 22 to 44% and height by 19 to 51%. Kernel weight was significantly affected in some of the susceptible lines. All three sources of resistance (Wsm1, Wsm2, c2652) and Wsm2 derivatives protected wheat against infection despite repeated inoculation. Inoculated resistant plots were virtually disease free and suffered neither significant yield loss nor height reduction. National yield trials of the breeding derivatives showed no difference in yields between those with and without Wsm2 under non-WSMV conditions.


The screening of wheat germplasm for resistance to stripe and leaf rust in Kazakhstan using molecular markers

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Life Sciences 6 (9) : 353-362, 2012

A. Kokhmetova, G. Yessenbekova, A.I. Morgounov and F. Ogbonnaya

Resistance to stripe and leaf rusts is the most important objectives in Kazakhstan, and they are the major factor that adversely affects wheat yield and quality and finally causes considerable economic damage. This study was aimed at characterizing elite wheat germplasm from Central Asia using molecular markers linked to the Lr34/Yr18 dual rust resistance gene and to identify new wheat germplasm resistant to leaf and yellow rust. In experiment with germplasm developed from Kazakhstan and Central and West Asia yellow rust trap nursery (CIMMYT), the frequency of the csLV34b-allele linked to Lr34/Yr18 (150 bp) was low and only seven of the 42 accessions had allele diagnostic of Lr34/Yr18. Two genotypes had high level of resistance, showing immune reaction to all three rusts. Disease severity from resistance to moderate susceptible was recorded in the lines having Lr34/Yr18 genes, which is comparable to the disease severity observed on the cultivar, Cook (20MS-30MS), carrying Lr34/Yr18 genes. The molecular screening of a set of additional 51 wheat genotypes, including commercial cultivars and breeding lines from different countries, showed that the csLV34 marker was present in 20 genotypes. This allowed us to select lines that could be used for future breeding work. In all, a total of 269 lines possessed effective Lr34/Yr18 gene complex: 28 lines of F4 Almaly/Opata-85, 34 lines of Almaly/Super Kauz, 26 lines of F4 Parula/(Almaly/Anza), 23 lines of F4 Babax 1/Opata 85, and 27 lines of Madsen/Cook populations. This further validates and confirms that the STS marker csLV34 and morphological marker leaf tip necrosis are reliable in the identification of carriers of effective slow rusting Lr34/Yr18 gene. The germplasms identified are further being tested for end-used quality and could be released by NARS as varieties in the various countries of Central Asia.

Identification of new maize inbred lines with resistance to Striga hermonthica (Del.) Benth

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Crop Protection 1 (2): 131-142, 2012

Haron Karaya, Njoroge Kiarie, Stephen Mugo, Fred Kanampiu, Emmanuel Ariga and John Nderitu

Striga hermonthica is a noxious, obligate hemi-parasite of cereal grasses that causes severe grain yield loss in susceptible maize cultivars in Africa. The development of host plant resistance is one of the most practical Stiga control strategies. In this study experiments on 36 maize inbred lines were conducted in pots and in field during the two rainy seasons of 2009 at Kibos and Alupe stations in Kenya. This study was carried out in order to determine the variation in Striga emergence, and the correlation between the attachments of the parasite to the roots. Significant differences (P < 0.001) were detected among the inbred lines for grain yield under Striga-free environment. The Striga damage rating (SDR) was significant (P < 0.05) among the inbred lines. A highly significant and negative correlation coefficient was observed between grain yield and Striga damage rating (r = – 0.67). Positive correlation coefficients were observed between grain yield and ear aspect (r = 0.46) and plant aspect (r = 0.75), respectively. For the experiment in pots, highly significant differences (P < 0.01) were observed among the inbred lines for Striga resistance traits. Striga attachments were found to be correlated with the number of emerged Striga plants. A significant correlation was found between Striga attachments and Striga counts in pots at the 10th week after planting (WAP) (r = 0.25) and the 14th WAP (r = 0.31). Inbred lines JI-30-19 and OSU231//56/44-6-4-17-3 were identified as the most resistant lines as they consistently performed well in both Striga-free and Striga-infested environments. These inbred lines could be used for breeding Striga-resistant maize varieties.

Multi-trait and multi-environment QTL analyses for resistance to wheat diseases

Posted by Carelia Juarez on , in Journal Articles

Published in PLoS ONE 7 (6): e38008, 2012

Sukhwinder-Singh, Mateo V. Hernandez, Jose Crossa, Pawan K. Singh, Navtej S. Bains, Kuldeep Singh, Indu Sharma


Stripe rust, leaf rust, tan spot, and Karnal bunt are economically significant diseases impacting wheat production. The objectives of this study were to identify quantitative trait loci for resistance to these diseases in a recombinant inbred line (RIL) from a cross HD29/WH542, and to evaluate the evidence for the presence loci on chromosome region conferring multiple disease resistance.

Methodology/Principal Findings

The RIL population was evaluated for four diseases and genotyped with DNA markers. Multi-trait (MT) analysis revealed thirteen QTLs on nine chromosomes, significantly associated with resistance. Phenotypic variation explained by all significant QTLs for KB, TS, Yr, Lr diseases were 57%, 55%, 38% and 22%, respectively. Marginal trait analysis identified the most significant QTLs for resistance to KB on chromosomes 1BS, 2DS, 3BS, 4BL, 5BL, and 5DL. Chromosomes 3AS and 4BL showed significant association with TS resistance. Significant QTLs for Yr resistance were identified on chromosomes 2AS, 4BL and 5BL, while Lr was significant on 6DS. MT analysis revealed that all the QTLs except 3BL significantly reduce KB and was contributed from parent HD29 while all resistant QTLs for TS except on chromosomes 2DS.1, 2DS.2 and 3BL came from WH542. Five resistant QTLs for Yr and six for Lr were contributed from parents WH542 and HD29 respectively. Chromosome region on 4BL showed significant association to KB, TS, and Yr in the population. The multi environment analysis for KB identified three putative QTLs of which two new QTLs, mapped on chromosomes 3BS and 5DL explained 10 and 20% of the phenotypic variation, respectively.


This study revealed that MT analysis is an effective tool for detection of multi-trait QTLs for disease resistance. This approach is a more effective and practical than individual QTL mapping analyses. MT analysis identified RILs that combine resistance to multiple diseases from parents WH542 and/or HD29.

Improved winter wheat genotypes for Central and West Asia

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2012

R. C. Sharma, S. Rajaram, S. Alikulov , Z. Ziyaev, S. Hazratkulova , M. Khodarahami , S. M. Nazeri, S. Belen, Z. Khalikulov, M. Mosaad, Y. Kaya, M. Keser, Z. Eshonova,  A. Kokhmetova, M. G. Ahmedov, M. R. Jalal Kamali  and A. I. Morgounov

High grain yield and resistance to stripe (yellow) rust are the most important traits for successful adoption of winter wheat varieties in Central and West Asia. This study was conducted to determine the stripe rust response and agronomic performance of a set of breeding lines recently developed by the International Winter Wheat Improvement Program (IWWIP). Replicated field studies were conducted in 2010 and 2011 using 38 experimental lines, one regional check (Konya) and one local check. Stripe rust scores were recorded at Karshi, Uzbekistan, and Karaj and Mashhad, Iran, in 2010. Grain yield was recorded at two sites each in Uzbekistan (Karshi and Kibray) and Iran (Karaj and Mashhad) and one site in Turkey (Eskisehir). The test lines showed variation for stripe rust severity, grain yield, 1,000-kernel weight, days to heading and plant height. Several stripe rust resistant genotypes were either higher yielding or equal to the local checks at different sites. Based on stripe rust resistance and yield performance in 2010, a set of 16 genotypes was selected and evaluated in 2011. All 16 were resistant at Almaty, Kazakhstan, and Dushanbe, Tajikistan, in 2011, whereas 9 of the 16 were resistant at Terter, Azerbaijan. The genotypes ‘TCI-02-138, ‘Solh’, ‘CMSS97M00541S’, ‘TCI -2-88(A)’ and ‘TCI-02-88(C)’ were consistently resistant to stripe across all sites in both years. Several lines showed high grain yields and superior agronomic performance across four sites in Uzbekistan and one site in Tajikistan. One genotype has been released in Uzbekistan and another in Tajikistan.


The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production

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Published in  Annual Review of Phytopathology 49: 465-481, 2011

The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production

Ravi P. Singh, David P. Hodson, Julio Huerta-Espino, Yue Jin, Sridhar Bhavani, Peter Njau, Sybil Herrera-Foessel, Pawan K. Singh, Sukhwinder Singh and Velu Govindan

Race Ug99 of the fungus Puccinia graminis tritici that causes stem or black rust disease on wheat was first detected in Uganda in 1998. Seven races belonging to the Ug99 lineage are now known and have spread to various wheat-growing countries in the eastern African highlands, as well as Zimbabwe, South Africa, Sudan, Yemen, and Iran. Because of the susceptibility of 90% of the wheat varieties grown worldwide, the Ug99 group of races was recognized as a major threat to wheat production and food security. Its spread, either wind-mediated or human-aided, to other countries in Africa, Asia, and beyond is evident. Screening in Kenya and Ethiopia has identified a low frequency of resistant wheat varieties and breeding materials. Identification and transfer of new sources of race-specific resistance from various wheat relatives is underway to enhance the diversity of resistance. Although new Ug99-resistant varieties that yield more than current popular varieties are being released and promoted, major efforts are required to displace current Ug99 susceptible varieties with varieties that have diverse race-specific or durable resistance and mitigate the Ug99 threat.


Global status of wheat leaf rust caused by Puccinia triticina

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Published in Euphytica 179(1): 143-160

Global status of wheat leaf rust caused by Puccinia triticina

J. Huerta-Espino, R. P. Singh, S. Germán, B. D. McCallum, R. F. Park, W. Q. Chen, S. C. Bhardwaj and H. Goyeau

Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.

Genetics and mapping of resistance to spore inoculum and culture filtrate of Phaeosphaeria nodorum in spring wheat line

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Published in Crop Protection 30(2): 2011

Genetics and mapping of resistance to spore inoculum and culture filtrate of Phaeosphaeria nodorum in spring wheat line ND 735

P.K. Singh; M. Mergoum; T.B. Adhikari; F. Ghavami; and S.F. Kianian

Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, is one of the most devastating foliar diseases on wheat (Triticum aestivum L.) in the northern Great Plains of North America. This study was conducted, under controlled environmental conditions, to elucidate the genetics and map the resistance to SNB caused by spore inoculum and culture filtrate of P. nodorum isolate Sn2000. A hard red spring wheat population was developed from a cross between the susceptible cultivar Steele-ND and the resistant line ND 735 for this study. Two-leaf seedlings of the parents, F1 and F2 generations, and F2:6 recombinant-inbred lines (RILs) were inoculated with spore suspensions while independent two week old seedlings of segregating generations were infiltrated with culture filtrate. Disease reaction was assessed 8 days after inoculation based on a lesion-type scale while plants were evaluated for culture filtrate response four days after infiltration for the presence or absence of necrosis. Genetic analysis revealed that a single recessive gene, Tsn1, in ND 735 confers resistance to both spore suspension and culture filtrate of P. nodorum isolate Sn2000. Mapping analysis using Diversity Arrays Technology (DArT) and simple sequence repeat (SSR) markers indicates the gene, Tsn1, is located on the long arm of chromosome 5B and is flanked by the DArt markers wPt-8285 and wPt-3049 at a distance of 7.0 cM and 2.9 cM, respectively. This gene also controls resistance to tan spot caused by Pyrenophora tritici-repentis race 2. Results of this study reveal that wheat-P. nodorum interaction follows the toxin model of gene-for-gene hypothesis. Additionally, the finding of single gene control in the line ND 735 for both tan spot and SNB enhances the utility of the line ND 735 in wheat breeding program as a source of multiple disease resistance.

Gene-specific markers for the wheat gene Lr34/Yr18/Pm38 which confers resistance to multiple fungal pathogens

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Published in Theoretical and Applied Genetics 119(5): 889-898

Gene-specific markers for the wheat gene Lr34/Yr18/Pm38 which confers resistance to multiple fungal pathogens

Evans S. Lagudah, Simon G. Krattinger, Sybil Herrera-Foessel, Ravi P. Singh, Julio Huerta-Espino, Wolfgang Spielmeyer, Gina Brown-Guedira, Liselotte L. Selter and Beat Keller

The locus Lr34/Yr18/Pm38 confers partial and durable resistance against the devastating fungal pathogens leaf rust, stripe rust, and powdery mildew. In previous studies, this broad-spectrum resistance was shown to be controlled by a single gene which encodes a putative ATP-binding cassette transporter. Alleles of resistant and susceptible cultivars differed by only three sequence polymorphisms and the same resistance haplotype was found in the three independent breeding lineages of Lr34/Yr18/Pm38. Hence, we used these conserved sequence polymorphisms as templates to develop diagnostic molecular markers that will assist selection for durable multi-pathogen resistance in breeding programs. Five allele-specific markers (cssfr1cssfr5) were developed based on a 3 bp deletion in exon 11 of the Lr34-gene, and one marker (cssfr6) was derived from a single nucleotide polymorphism in exon 12. Validation of reference genotypes, well characterized for the presence or absence of the Lr34/Yr18/Pm38 resistance locus, demonstrated perfect diagnostic values for the newly developed markers. By testing the new markers on a larger set of wheat cultivars, a third Lr34 haplotype, not described so far, was discovered in some European winter wheat and spelt material. Some cultivars with uncertain Lr34 status were re-assessed using the newly derived markers. Unambiguous identification of the Lr34 gene aided by the new markers has revealed that some wheat cultivars incorrectly postulated as having Lr34 may possess as yet uncharacterised loci for adult plant leaf and stripe rust resistance.

New and diverse sources of multiple disease resistance in wheat

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Published in Crop Science 49(4): 1655-1666

New and Diverse Sources of Multiple Disease Resistance in Wheat

Suraj Gurung, J. Michael Bonman, Shaukat Ali, Jaimin Patel, Mary Myrfield, Mohamed Mergoum, Pawan K. Singh and Tika B. Adhikari

Tan spot (caused by Pyrenophora tritici-repentis) and Stagonospora nodorum blotch (SNB), (caused by Phaeosphaeria nodorum) are destructive diseases of wheat (Triticum aestivum L.). The majority of currently grown wheat varieties are susceptible to both diseases, presumably because of high pathogenic variability occurring in these fungi or narrow genetic background for resistance in wheat varieties. Therefore, identifying new sources of tan spot and SNB resistance in wheat is imperative. A subset of 825 wheat accessions from the core collection of the National Small Grains Collection (NSGC) of the United States Department of Agriculture, National Plant Germplasm System (NPGS) was evaluated for resistance to tan spot and SNB at seedling stage in a growth chamber. On the basis of disease reactions, 88 wheat accessions exhibited resistance to both diseases. Data from the Germplasm Resources Information Network (GRIN) were examined for the 88 accessions to identify those that also have resistance to other key diseases and on this basis 28 accessions with multiple resistances were identified. The genetic relationship among the 88 accessions was assessed using resistance gene analog polymorphism (RGAP) primers. Wheat accessions with similar growth habit were grouped together despite differences in country of origin. Associations between agronomic traits and host resistance indicated that winter wheat habit in the studied collection was strongly associated with both SNB and tan spot resistance. This study identified genetically diverse wheat accessions with broad-spectrum resistance that can be used in developing cultivars with high levels of resistance to multiple diseases in wheat breeding programs.