Ayub Agricultural Research Institute, Faisalabad, Pakistan
Muhammad,Idrees, Faqir, Muhammad, Arshad, Mehmood, Majid, Nadeem, Saleem-ur, Rehman, Makhdoom, Hussain, Javed, Ahmad, , , , , , , , , , , , , , , ,
Under changing climatic conditions, the emergence of new diseases or new races of existing diseases is a serious threat to global wheat production. Particularly, the presence of wheat blast in Bangladesh and stem rust race Ug99 in Iran, created a fearsome and intractable situation for Pakistan. A study was planned for monitoring and surveillance of the wheat blast and rust pathogens in wheat growing districts of Punjab, Pakistan during the cropping season 2016-17 as vigilance program. During the survey, one hundred and seventy one wheat fields of upper and central Punjab region were monitored and two types of Rusts (Leaf Rust & Yellow Rust) were recorded in varying intensity on different varieties of wheat. Out of 171 locations 86 spots were free from both types of rusts i.e. Leaf Rust & Yellow Rust, while the remaining locations were found to be infected with both leaf and yellow rust. However, all the surveyed fields were free from the stem rust infestation. Among the infected fields, 23 were infected by Leaf Rust while 63 fields were infected by Yellow Rust.The susceptible type of rust attack was noticed on old/ banned/ unapproved wheat varieties. Moderately resistant to resistant reaction was observed on newly approved varieties. The rust infected samples having S or MS type infection were collected for race analysis. Similarly, blast suspected samples were analyzed in laboratory and none of the tested samples showed the presence of wheat blast pathogen, which indicates no need to panic but vigilant in future.
QAAFI, The University of Queensland
Robert McIntosh, Peng Zhang, Sami Hoxha, Adnan Riaz, Burkhard Steuernagel, Brande Wulff, Evans Lagudah, Lee Hickey, Sambasivam Periyannan
Wheat is one of the most important staple food and agricultural crop cultivated worldwide. To meet the demands of the raising human population, global wheat production has to be increased which is however declined due to appearance of highly virulent strains of Puccinia striiformis f. sp. tritici (Pst) fungus causing stripe rust disease. Globally, the incidence of stripe rust is effectively managed through the deployment of host plant mediated genetic resistance. But as the resistance present in the current wheat cultivars are ineffective, new sources of resistance particularly from pathogen unexposed genetic resources are of urgent need to prevent stripe rust epidemics. Landrace collections with rich genetic diversity and being less exposed to prevalent pathogen are of valuable source for resistance to new pathogens. In this study, a total of 295 landrace accessions collected by the famous Russian botanist Vavilov was screened for stripe rust resistance using the two predominant lineage Pst strains of Australia. Six accessions with good resistance against the two aggressive Pst strains were selected for genetic characterization and for utilization in global wheat breeding. Characterisation of these novel resistance were undertaken using combination of conventional and advanced genetic tools. While the conventional approach involves the traditional map based gene cloning, the other tool is the recently identified rapid method based on mutagenesis, targeted gene capture and next generation sequencing called "MutRenSeq". Subsequently, the identified novel resistant traits were transferred into elite wheat cultivars through the combination of linked molecular markers and speed breeding techniques. Thus along with the identification of novel resistance, elite wheat cultivars with broad spectrum stripe rust resistance were also generated through the use state of art techniques to sustain global wheat production from the rapidly evolving stripe pathogens.
University of Minnesota
Michael Pumphrey, Matthew Rouse
Stem rust of wheat caused by the fungal pathogen Puccinia graminis f. sp. tritici historically caused major yield losses of wheat worldwide. To understand the genetic basis of stem rust resistance in contemporary North American spring wheat, genome-wide association analysis was conducted on 250 elite lines. The lines were evaluated in separate nurseries each inoculated with a different P. graminis f. sp. tritici race for three years (2013, 2015 and 2016) at Rosemount, Minnesota. The lines were also challenged with the same four races at the seedling stage in a greenhouse facility at the USDA-ARS Cereal Disease Laboratory. A total of 22,310 high-quality SNPs obtained from the Infinium 90,000 SNPs chip were used to perform association analysis. Markers strongly associated with resistance to the four races at seedling and field environments were identified. At the seedling stage, the most significant marker-trait associations were detected in the regions of known major genes (Sr6, Sr7a and Sr9b) except for race QFCSC where a strong association was detected on chromosome arm 1AL. Markers presumably linked to Sr6 and Sr7a were associated with both seedling and field resistance to specific races. A field resistance QTL on chromosome arm 2DS was detected for response to races RCRSC and TPMKC. A QTL specific to field resistance was detected for QFCSC and TPMKC on 2BL. The markers that showed strong association signals may be useful to pyramid and track race-specific stem rust resistance genes in wheat breeding programs. We postulated the presence of Sr2, Sr6, Sr7a, Sr8a, Sr9b, Sr11, Sr12, Sr24, Sr25, Sr31, and Sr57 (Lr34) in this germplasm based on phenotypic and marker data. We found that combinations of genes conferring resistance to specific P. graminis f. sp. tritici races accounts for the prevalent stem rust resistance in North American spring wheat.
The University of Agriculture, Peshawar, Pakistan
Muhammad,Khan, Safi, Kathi, Zahoor, Swati, Manzoor, Hussain, Annemarie, Justesen, Muhamamd, Imtiaz, , , , , , , , , , , , , , , , , ,
Considering the importance of wheat rust diseases in Pakistan and the recent identification of yellow rust pathogen (Puccinia striiformis f. sp. tritici) centre of diversity in Pakistan, the present study was designed to assess the status of three wheat rusts across the country during 2015-16 and 2016-17 and analyze the population structure of P. striiformis f. sp. tritici . A total of 451 fields (from 68 districts) were surveyed during 2016 and 480 fields (from 69 districts) during 2017. A high yellow rust pressure was present during 2016 throughout Pakistan, while it was predominant only in the Northern half during 2017. Leaf rust was present in the central part of the country, while stem rust was only found in the south. In Sindh province (located in the south), yellow rust was reported unexpectedly with high severity (>60%) on varieties like Kiran and Galaxy during both the years. A set of 513 samples of P. striiformis were genotyped with microsatellite markers to assess the population diversity and spatial structure. and infer on the cause of epidemics in the Sindh province. Population genetics analyses confirmed a recombinant population structure across all locations except the Sindh province, where relatively lower diversity and lack of recombination signature was revealed. At least five genetic groups were identified in the overall population, which were found across all locations, except Sindh province where one of the genetic groups was predominant. The P. striiformis population from Sindh province with low diversity that caused unexpected epidemics in a relatively warmer region needs to be further investigated for specific adaptation traits. Our results confirmed the high diversity across Pakistan, which lies in the Himalayan centre of diversity of the pathogen. This high diversity was present in locations without the presence of alternate host (Berberis spp.) and could potentially be associated with regular migrants from the Berberis zone into the whole country.
Crop and Horticultural Science Research Department, Ardabil Agricultural and Natural Resources Research and Education Center, Ag
Yellow (stripe) rust caused by Puccinia striiformis f. sp. tritici is the most devastating disease of bread wheat (Triticum aestivum) in the world. A wide range of virulent yellow rust pathotypes is evolving in different regions of the world causing the breakdown of widely utilized sources of resistance in wheat. Hence, the knowledge of virulence factors of pathogen and determining of effective resistance genes in the region will enable breeders to target those useful genes in their breeding programs. During cropping seasons of 2015-2016 and 2016-2017, virulence of the wheat yellow rust was investigated by planting differential cultivars and isogenic lines in a yellow rust trap nursery in Ardabil, northwest of Iran . Results showed stripe rust infections on some cultivars carrying Yr genes such as Yr1, Yr3, and Yrsp previously known to be resistant. The virulence spectrum of race population in Ardabil was identical to the Warrior race or its variants which is different from characterized races in Ardabil by carrying virulence combination for Yr1, Yr3, Yr17, Yr32, and YrSP and is avirulent on Yr8 and Yr27. Except for Yr8, Yr17 and Yr27, the common races in Ardabil are generally avirulent on Yr1, Yr3, and YrSP. This is the first report of race population in Ardabil (Iran) which is similar to the Warrior race or its variants.
Department of Field Crops, Ege University, Izmir, Turkey
Kumarse Nazari, Mehran Patpour, Davinder Singh, Aladdin Hamwieh
Rust diseases in wheat are the major threat to wheat production and yield gains. The breakdown in resistance of certain major genes and new emerging aggressive races of rusts are causing serious concerns in all main wheat growing areas of the world. Therefore, it is the need of the hour to search for new sources of resistance genes or QTL's for effective utilization in future breeding programs. In total 100 wheat genotypes were evaluated for seedling and adult-plant resistance to stem rust races TKTTF and TTKSK at Tel Hadya-Syria, and Njoro-Kenya, and Kelardasht-Iran. Evaluation to Yr27 virulent stripe rust race was carried out at Tel Hadya and Terbol-Lebanon research stations. In this study we used genome wide association studies (GWAS) to identify markers or QTLs linked to stem rust and stripe rust races using Diversity Arrays Technology (DArT?) in selected 35 Iranian wheat genotypes. The association of markers and phenotypes was carried out using a unified mixed-model approach (MLM) as implemented in the genome association and prediction integrated tool (GAPIT). Out of 3,072 markers, 986 were polymorphic and used for marker trait associations. A total of 44 DArT markers were identified to be significantly (p<=0.01) associated with studied traits in 16 genomic regions 1A, 1B, 2A, 4A, 6A, 7A, 1B.1R, 2B, 3B, 4B, 5B, 5B.7B, 6B, 7D and an unknown region. Among associated markers, 34 were linked to stem and nine to stripe rust. They were found on 16 genomic regions on chromosome arms 1A, 1B, 2A, 4A, 6A, 7A, 1B.1R, 2B, 3B, 4B, 5B, 5B.7B, 6B, 7D and an unknown region. Associated markers explained phenotypic variation ranging from 21 to 65%. In addition to validation of previously identified genes, this study revealed new QTL's linked to stem and stripe rust which will assist breeders to develop new resistant varieties.
Jamal El Haddoury, Ahmed Amri
Malika', a hard red spring wheat (Triticum aestivum L.) cultivar developed using doubled haploid technology by the Institut National de la Recherche Agronomique (INRA), Morocco, and tested as 06DHBW48, was approved for release in 2016 by the Office National de S?curit? Sanitaire des Produits Alimentaires (ONSSA), Morocco. Malika was selected from the doubled haploids derived from the cross 'Achtar3*//'Kanz'/Ks85-8-4). Achtar and Kanz are Moroccan varieties originating from segregating populations from CIMMYT. Achtar and Kanz are a well adapted to Moroccan conditions but susceptible to the Hessian fly, yellow rusts and some races of leaf rust. 'Achtar' was crossed with it in order to incorporate the Hessian fly resistance, yellow rust resistance and leaf rust resistance and 'Achtar' was crossed with Kanz/Ks85-8-4 having resistance to Hessian fly, yellow rust and leaf rust. Backcrossed 3 times with 'Achtar', and selected lines having resistance to the Hessian fly, yellow rust and leaf rust from the population derived from each backcross. Finally the selected the resistant line was used develop doubled haploids. The doubled haploid lines produced were tested in the laboratory and field for Hessian fly and the rust resistance. The resistant lines were incorporated in the multi-local yield trials and three promising lines with the resistance to Hessian fly, yellow rust and leaf rust and better yield and quality were submitted for registration in the official catalog in 2014. After 2 years of testing (years 2014-15 and 2015-16), one line (06DHBW48) was accepted for the registration and designated as 'Malika'. 'Malika' is a semi-dwarf variety, well adapted to semi-arid regions, early maturing, high yielding, tolerant to drought and resistant to Hessian fly, leaf rust and yellow rust.
Bangladesh Agricultural Research Institute
Paritosh Kumar,Malaker, Krishna Kanta, Roy, Md. Mostofa Ali, Reza, Naresh Chandra Deb, Barma, Md., Farhad, , , , , , , , , , , , , , , , , , , ,
Leaf rust is one of the major diseases of wheat in Bangladesh. The farmer fields and trial sites were regularly surveyed for rust assessment from 2010-2011 to 2016-2017 wheat growing seasons. Disease severity was recorded following BGRI protocols. Percentage of fields infected with leaf rust and the levels of disease severity varied with genotype, year, planting time and survey sites. Timely planted wheat either escaped or had less disease compared to late planted crop. Among our cultivated varieties, Shatabdi was either free from infection or exhibited only trace severity with resistant reaction. Variety Saurav, Bijoy, BARI Gom 27 , BARI Gom 28 , BARI Gom-29 and BARI Gom-30 were consistently free from leaf rust infection. BARI Gom 25 and BARI Gom 26 showed low to moderate disease levels with MRMS-MSS reactions, while the variety Prodip demonstrated moderate to high disease severity with susceptible response and it needs to be replaced by resistant variety to sustain wheat productivity.
Wheat Research Institute, AARI, Faisalabad, Pakistan
Ghulam Mahboob Subhani, Makhdoom Hussain, Mehvish Makhdoom
Rust is the single largest factor limiting wheat production in Pakistan. According to the FAO reports, countries in the predicted immediate pathway of Ug99 grow more than 65 million hectares of wheat, accounting for about 25% of global wheat harvest.
Rice, a member of the same family (Poaceae) is not attacked by any rusts. Wheat, an allo-hexaploid is responsive for wide crossing. It has previously been successfully crossed with its several wild relatives and different other crop species like corn, pearl millet etc. Based on the above facts wheat ? wild rice crossing has been attempted to incorporate rust resistance from rice to wheat. Successful crosses were made under in-vitro conditions. Surviving plantlets developed from these crosses were assayed for any genetic material introgressed from rice. Different cytological / molecular techniques were used to detect the introgression (Squash preparations from root tips, FISH, GISH, SSR etc.). Two hundred and fifty primers specific to rice chromatin were used to look for the introgression of rice chromatin into hybrids. Seven primers amplified the fragments in hybrids indicating the possible introgression of rice chromatin in wheat x rice hybrids but in-situ hybridization didn't confirm that introgression. So further testing of these hybrids is needed.
La Trobe University
Reem Joukhadar, Sukhwinder Singh, Francis Ogbonnaya
Synthetic hexaploid wheat (SHW), generated by crossing Triticum turgidum (AABB) with Aegilops tauschii (DD), has been exploited in improving various traits in cultivated wheat. A number of recent studies decomposed the additive variance of different traits captured by multiple sets of variants (e.g. single nucleotide polymorphisms (SNPs) located on different chromosomes or genic/intergenic regions) in both human and animal quantitative genetics studies. In this research, we dissected the additive variance explained by the three subgenomes and seven homoeologous sets of chromosomes in SHW germplasm to gain a better understanding of trait evolution in newly synthesized wheat. Our SHW germplasm lines generated by crossing improved durum parents (AABB) with Aegilops tauschii (DD) parents were phenotyped for ten fungal/nematode resistance traits. The lines were genotyped by genotyping-by-sequencing and 6,176 SNPs were mapped with missing data of less than 20%. The D subgenome dominated the additive effects and this dominance affected the A more than the B subgenome. The D subgenome exhibited a 1.8-fold higher contribution than the A subgenome across all traits. This dominance was not inflated by population structure or by longer linkage disequilibrium blocks observed in the D subgenome. The cumulative effects of the three homoeologs in each set had a significant positive correlation with their cumulative explained additive variance. Moreover, an average of 70% for each chromosomal group cumulative additive variance came from one homoeolog that had the highest explained variance within the group across all ten traits. We hypothesize that structural and functional changes during diploidization may explain chromosomal group relationships as allopolyploids maintain a balanced dosage for many genes. Our results contribute to a better understanding of trait evolutionary mechanisms in SHW, and will facilitate effective utilization of wheat relatives in breeding.