Agricultural Biotechnology Research Institute, Ayub Agricultural Research Institute (AARI), Faisalabad-Pakistan
Imran Habib, Sajid-ur-Rahman, Muuhammad Waqas Jamil, Muhammad Zaffar Iqbal
Rust diseases are among the most important affecting wheat because they are responsible for a significant yield reduction globally. Different types of conventional breeding approaches are currently underway to protect wheat from these diseases. The involvement of molecular genetics and biotechnology tools in conventional plant breeding sets new directions to develop crop varieties with desired traits more efficiently and accurately. An array of molecular markers linked to rust resistant genes and dense molecular genetic maps are now available for use. Marker assisted selection (MAS) is now a routine activity in various crops especially for agronomic traits that are otherwise difficult to tag like resistance to pathogens, insects, nematodes etc. Gene pyramiding involves the stacking of many genes leading to real-time expression of all genes in single variety to develop durable resistance. This method is gaining significant popularity as it would enhance the efficiency of conventional breeding methods and precise development of broad spectrum resistant capabilities. Keeping in view the significance of MAS, rust resistant wheat parental lines were selected and molecular information was tagged using gene linked markers through PCR. Conventional breeding plane was designed on the basis of molecular data and maximum crosses were made between high yielding susceptible and resistant wheat genotypes. Molecular screening and other yield parameters were keenly noted on each stage of segregating population. Three rust resistant genes i.e. Lr-34/Yr-18, Lr-46/Yr-29 and Lr-19 were successfully combined in three cross combinations. Twenty crosses were found positive for two resistant genes i.e. Lr-46/Yr-29 and Lr-19, Moreover, one cross was positive for Lr-34/Yr-18 and Lr-46/Yr-29, and one was positive for Lr-34/Yr-18 and Lr-19. Introduction of more genes is also continued to develop superior resistance against a wide range of rust pathogen in wheat.
Sher-e-kashmir University of Agricultural Sciences and Technology of Kashmir, Jammu and kashmir, India
Reyazul Rouf Mir, Shazia Mukhtar, Rahul R., Nelwadker, M., Ashraf Bhat
In India stripe rust of wheat (Triticum aestivum L.) is important as it occurs in the severe form in North Hill Zone (NHZ) covering states of Jammu and Kashmir, Himachal Pradesh and Uttarakhand. Stripe rust thrives well under cool and moist field conditions and sometimes its epidemic is so severe that it destroys the whole crop. Although the fungicides have been applied to control this disease but their use is unfriendly to the environment and they add to the input cost of farmers. The breeding for disease resistance is an effective strategy and involves identification of stable sources of resistance and their utilization. Deployment of yellow resistance genes has helped in suppressing the intensity, effectiveness and frequency of rust epiphytotics. Many sources of yellow rust resistance exist, but these are either incompletely characterized or these have not been studied in sufficient detail needed for their designation. The present study was conducted to screen for yellow rust resistance a set of 300 wheat germplasm lines received from various national and international germplasm centers viz., CIMMYT, Mexico; CIMMYT, Ankara, Turkey; IARI sub-station, Wellington, Tamil Nadu; IIWBR, Karnal; IIWBR, Flowerdale, Shimla and SKUAST-Kashmir, Srinagar for yellow rust resistance (46S119 and 78S84 as most prevalent races) over years 2012 to 2016 under field and ployhouse conditions. The study could identify eleven wheat lines showing varying levels of resistance to yellow rust races 46S119 and 78S84 when scored at adult plant stage under both conditions. The area under disease progress curve (AUDPC) scores of the lines identified as resistant was lowest as compared to yellow rust susceptible check (Agra Local). The resistant lines identified in the study could efficiently be utilized in yellow rust breeding programmes of the country and thereby deployment of such genes over space and time for an effective and long lasting control.
School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana-141004 India
Rohtas,Singh, Satinder, Kaur, Parveen, Chhuneja, , , , , , , , , , , , , , , , , , , , , , , ,
Leaf rust caused by Puccinia triticina is one of the most historical and economically important wheat diseases. Breeding for new cultivars with effective gene combinations is the most promising approach for reducing losses due to leaf rust. Wild emmer wheat, Triticum dicoccoides, the progenitor of modern tetraploid and hexaploid wheats, is an important resource for new variability for disease resistance genes. An accession of T. dicoccoides acc. pau4656 showed resistance against prevailing leaf rust races in India, when tested at the seedling and adult plant stage. The introgression line, developed from the cross of the leaf rust resistant T. dicoccoides acc. pau4656 and the susceptible T. durum cultivar Bijaga yellow, was crossed with T. durum cultivar PBW114 to generate recombinant inbred lines (RIL) for mapping leaf rust resistance gene(s). RIL population was screened against highly virulent leaf rust race 77-5 at seedling stage and inheritance analyses revealed the segregation of two leaf rust resistance genes. The genes have been temporarily designated as LrD1 and LrD2. A set of 387 SSR marker was used for bulked segregant analysis (BSA). The markers showing diagnostic polymorphism in the resistant and susceptible bulks were amplified on whole of the population. Single marker analysis using MapDisto software placed LrD1 on the long arm of chromosome 6A linked to the SSR marker Xwmc256 and LrD2 on long arm of chromosome 2A close to the SSR marker Xwmc632. T. durum cv. PBW114 used in the present study was also resistant to leaf rust at the seedling stage. So one of these leaf rust resistance genes might have been contributed by the PBW114 and other by T. dicoccoides. The current study identified valuable leaf rust resistance genes for deployment in wheat breeding programme.
Plant Pathology Division, Nepal Agricultural Research Council
Baidya Nath Mahto, Durba Bahadur, Thapa Roshan, Basnet Nautan Raj, Gautam Sesh, Raman Upadhyaya
Disease surveillance is very important in establishing the status of disease response in crops. During the 2014 to 2016 wheat seasons, foliar blight (spot blotch caused by Bipolaris sorokiniana and tan spot caused by Pyrenophora tritici-repentis) was recorded as severe across the entire whole plains region. Foliar blight was moderate in the mid hills, especially the Kathmandu valley. Leaf rust was severe (10MS - 100S) at several places in the mid hills. This could be due either to climatic conditions or varieties susceptible to the prevailing pathotypes. Yellow rust was also recorded up to 100S in the Kathmandu valley. Newly released varieties Gaura and Dhaulagiri showed yellow rust incidence of 20MS to 40S. Stem rust was sporadic and light and was observed very late in the season (tR - 10MR) in far western districts and the Kathmandu valley. Powdery mildew was moderate and localized. Loose smut was found at low levels throughout the mid hills. In 2014, Karnal bunt (caused by Tilletia indica) was also recorded in far western regions. Five different pathotypes of P. triticina (121R63-1, 21R55, 21R63 and 0R9) and one Pst pathotype (110S119) have prevailed during the last few years. Wheat genotypes were evaluated at Khumaltar and those reputed to have Yr27, Yr27+, Yr27+Yr18, Yr31+APR, Yr9, Yr10 and Yr15 were resistant. Similarly, genotypes containing Lr34+ had lower leaf rust severities than others.
Mohamed 5 university/ICARDA
Amadou tidiane sall, meryem zaim, Ayed Al-abdallat, Gregor Gorjanc, Jesse Poland, Miloudi Nachit, Abdel karim Filali Maltouf, Bouchra Belkadi, Rodomiro Ortiz, Filippo Bassi
Durum wheat production is globally important, but grain yield has been stagnating in recent decades. In order to ensure that its production maintains the pace with increasing demand, breeding for high grain yield must be supported by molecular-based methods. Genomic estimated breeding values for selection and genome scan were assessed as molecular tools holding maximum potential for durum wheat breeding. Four recombinant inbred line populations bred by inter-mating elite were sown in yield trials at five sites. All progenies were characterized using "genotyping by sequencing" method. A consensus map was developed, and missing genotypes were imputed using a Hidden Markov model to reach a total of 1987 polymorphic markers. Models accounting for genotype environment interactions were used to estimate the genetic component of each measured trait. Hence, Bayesian ridge regression was used to determine the predicted values and their relative accuracy in several combinations, testing full-sibs and half-sibs as training population for grain yield and 1,000 kernel weight. The high level of accuracy achieved suggests that GEBV for selection holds great potential for durum wheat breeding, as long as full-sibs are used as training populations, in combination with statistical models that account for G?E. In order to test the exploitability of genome scan to guide breeding crosses, a separate genome-wide association study was conducted. 288 elite were sown in the south of Morocco and at two sites along the Senegal River for two years. These sites show a temperature differential of 10?C. Implementing a GE model facilitated identifying the most heat tolerant among the tested entries. 8,173 polymorphic SNPs were inquired, and several associations could be identified between markers and the ability to withstand the heat gradient. Hence, GWAS holds great potential to increase genetic gain in breeding via increased accuracy in determining the crosses to be made.
All Russian Research Institute of Biological Plant Protection
Irina Petrovna Matveeva
Yellow rust caused by Puccinia striiformis West. is a harmful and dangerous disease in the south of Russia. Yield losses under optimum conditions on highly susceptible varieties can vary from 10 to 100%. During the growing season of 2017, cool weather with constant precipitation from the third decade of April to the first decade of June contributed to the intensive development of the pathogen. Surveys of the main winter wheat production areas in five agroclimatic zones of the region revealed that yellow rust was prevalent in all areas. The maximum development of P.striiformis was observed in southern submontane and western Priazovsky agroclimatic zones. Some varieties such as Grom, Yuka, Tanya, Anka had losses to yellow rust of up to 30-40 %. In the central and northern agroclimatic zones, the losses averaged 5%, whereas in the dry eastern steppe zone losses were only up to 1%. The build up of yellow rust inoculum in the region raises concerns that in 2018, under favorable weather conditions in spring, winter wheat crops could be infected with the disease, especially in the wetter agroclimatic zones.
Ebrahiem Babiker, Tyler Gordon, Sam Stoxen, Matthew Rouse, Yue Jin, Shiaoman Chao, John Bonman
Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a threat to wheat production worldwide. To manage this important disease, new sources of genetic resistance are needed and common wheat landraces are a potential source of such resistance. Landrace accessions from the USDA-ARS National Small Grains Collection were evaluated for seedling resistance to the Ug99 race group. To identify accessions most likely to carry novel resistance genes, a bulked segregant analysis (BSA) approach was used. Seven resistant accessions were crossed to a susceptible parent line and F3 families were tested against Pgt race TTKSK. The resistant plants were identified and grouped into two bulks per population. The bulks, along with the parents and F1 progeny, were genotyped with the 90K wheat iSelect SNP genotyping platform. Four of the populations appeared to segregate in a 1:1 phenotypic resistant/susceptible ratio, one in a 1:2 ratio, and two in 1:3 ratios. However, chi squared tests indicated the ratios were statistically the best fit for only two of the 1:1 segregating populations and one of the 1:3 segregating populations. Initial BSA results indicate the markers associated with reduced stem rust infection are located on wheat chromosomes 1DL and 2B. These mapping populations are being advanced for further evaluation to ascertain if novel resistance to the Ug99 stem rust race group is present.
Barani Agricultural Research Station, Kohat
Fida Mohammad, Muhammad Imtiaz
Stripe rust is one of the major limiting factors in wheat production. An objective-based breeding program was initiated at Barani Agricultural Research Station (BARS), Kohat in 2013/14 to transfer APR genes from CIMMYT and ICARDA spring wheat lines into wheat germplasm well adapted in Khyber Pakhtunkhwa (KPK). Nine high yielding but stripe rust susceptible KPK wheat varieties were crossed in various combination with 17 CIMMYT and ICARDA wheat lines carrying resistance genes. The resultant 79 F1s were backcrossed with respective susceptible parents followed by single plant selection in F2 generation. During 2015/16, 367 segregating populations/lines were screened in multi-environment stripe rust tests within Khyber Pakhtunkhwa. Sixty-nine out of 367 lines showing adequate resistance were again screened for strip rust resistance at hot spot and in yield trial at BARS, Kohat during 2016/17. Seventeen lines showed considerable resistance and were higher yielding than check cultivars. Lines exhibiting adequate resistance will be further tested in advanced yield trial at provincial and national level for possible release of new varieties in wheat.
Bogale Nigir, Cherinet Alem, Yosef G. Kidane, Mario Enrico Pè, Matteo Dell'Acqua
Septoria tritici blotch (STB) is a devastating fungal disease affecting durum and bread wheat cultivation worldwide. The search for resistance sources in untapped genetic resources may speed up breeding for STB resistance. Ethiopian durum wheat landraces represent a valuable source of allelic diversity for several traits, including disease resistance. In this study, we measure STB phenotypes under natural infection on two interconnected populations: i) a diversity panel comprising 318 Ethiopian durum wheat lines, mostly farmer varieties, and ii) a nested association mapping (NAM) population developed from a subset of the diversity panel. Phenology, yield and yield component traits were concurrently measured in the populations. We evaluated the distribution of STB resistance in Ethiopian genetic materials and the relationship existing between STB resistance and agronomic traits. STB resistance sources were found in landraces as well as in NAM lines. The genetic material was genotyped with more than 13 thousand genome-wide SNP markers to describe the linkage disequilibrium and genetic structure existing within the panels. The genotyping information was combined with phenotypes to identify marker-trait associations and loci involved in STB resistance. We identified several loci, each explaining up to 10% of the phenotypic variance for disease resistance. We developed KASP markers tagging the most interesting loci to allow the uptake of our results in a breeding perspective. Our results showed that the Ethiopian untapped allelic diversity bears a great value for studying the molecular basis of STB resistance and for breeding for resistance in local and international material.
University of Sydney Plant Breeding Institute
Naeela Qureshi, Vallence Nsaiyera, Pakeer Kandiah, Mesfin Gesesse, Mandeep Randhawa, Mumta Chhetri, Bosco Chenayek, James Kolmer, Miroslav Valarik, Zaroslav Dolezel, Beat Keller, Matthew Hayden, Justin Faris, Harbans Bariana, Vanessa Wells
Dr. Norman Borlaug stated that rust never sleeps and this enables rust pathogens to produce new strains capable of putting rust resistance genes to rest. These pathogens continue to pose threats to global wheat production. Wheat breeders have made significant progress to control rust outbreaks using conventional selection technologies; however, some critical shifts in pathogen populations have let them down. Rapid evolution in molecular marker technologies in the last 15 years and refinement of phenomic facilities have expedited the process of discovery and characterisation of rust resistance genes to underpin the development and validation of markers closely linked with genetically diverse sources of resistance. A high proportion of the formally named rust resistance genes were characterized in the 21st century and markers closely linked with these genes have been developed and validated. The marker tagged sources of resistance to three rust diseases have equipped the wheat breeding community with tools to deploy combinations of all stage and adult plant resistance genes in future wheat cultivars. The question that whether we have enough resistance genes discovered to compete against the ever-awake rust pathogens. In our opinion, we cannot be complacent and discovery needs to continue to ensure food security. This presentation will discuss the role of advances in phenomic and genomic technologies to achieve durable rust control in wheat.