School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana-141004 India
Ahmed Elkot, Satinder Kaur, Parveen Chhuneja
Stripe rust and leaf rust are two most widely distributed diseases of wheat despite the fact that major emphasis has been made globally to develop rust resistant varieties. The wild tetraploid wheat Triticum araraticum (AAGG) evolved in the eastern part of Fertile Crescent is a source of useful traits for the improvement of wheat including resistance to disease. T. araraticum acc. pau4692 and a derived advanced backcross introgression line (IL) in susceptible T. durum cv. Malvi local background showed high level of seedling resistance against Indian pathotypes of leaf rust and stripe rust. The F5 Single seed descent (SSD) population developed from the crosses between T. araraticum IL with T. durum cultivar PBW114 was screened with commonly prevalent pathotypes of leaf rust and stripe rust in India at the seedling stage. The genetic analysis indicated that the leaf rust resistance is conditioned by two genes and stripe rust resistance by a single gene. The SSR markers mapped on A and B genome were used for parental polymorphism along with resistant and susceptible bulks for leaf rust and polymorphic markers between bulks were used on the whole population. The molecular marker data using single marker analysis showed that leaf rust resistance genes were mapped on chromosome 2A and 7A linked to SSR markers Xwmc149 and Xbarc49, respectively. The genes have been temporarily named as LrAr1 and LrAr2. Bulked segregant analysis (BSA) for mapping stripe rust resistance is in progress.
Global Rust Reference Center (GRRC), Aarhus University, Denmark
Mogens Støvring Hovmøller, Jens Grønbech Hansen, Annemarie Fejer Justesen, Tine Thach, Julian Rodriguez-Algab, Dave Hodson, Biagio Randazzo
In 2016, severe epidemics of yellow (stripe) rust were observed on durum and bread wheat in European regions where the diseases in the past were insignificant or absent. Stem rust was also observed at epidemic levels for the first time in more than 50 years in Europe. On Sicily, both yellow and stem rust caused epidemics on cultivated durum and bread wheat and numerous breeding lines. In 2017, surveys in farmer fields and trial monitoring were carried out in Southern Italy during April-June. A total of 61 farmer fields and 9 experimental plots were inspected and rust samples collected. Despite unfavourable weather conditions for rust development, stem rust, yellow rust and leaf rust were detected on 86%, 50% and 14% of the surveyed sites, respectively. The surveys on Sicily covered approximately 70% of the durum wheat area, and data uploaded and visualised on the Wheat Rust Toolbox. On mainland Italy and Sardinia, yellow rust was observed, and sampled from nine fields in Sardinia and two in Puglia, whereas stem rust was detected and sampled in experimental plots in Sicily, Sardinia, Puglia, Lazio and Emilia Romagna. A total of 94 samples of stem rust, 30 samples of yellow rust, and 3 rust samples from Berberis aetnensis were sent to GRRC. Preliminary results of yellow rust genotyping and race phenotyping showed prevalence of race Triticale2015. Warrior(-) and a new race (Pst'New'- First detected in 2016) were also detected. For stem rust, TTTTF and TTRTF were detected in Sicily and mainland Italy and TKTTF was identified in Sardinia. Susceptibility of major commercial durum cultivars and breeding lines suggests the need for both durable resistance breeding and systematic surveys coupled to an early warning system.
University of Minnesota, St. Paul, MN 55108, U.S.A
Ruth Dill-Macky, Ruth Wanyera, Sridhar Bhavani, Worku Bulbula, Matthew Rouse
Stem rust caused by Puccinia graminis f.sp. tritici (Pgt) is one of the major constraints to wheat (Triticum aestivum) production worldwide. Pgt races have rapidly evolved in several geographical regions due to the deployment of single resistance genes resulting in boom and bust cycles, hence combinations of resistance genes through pyramiding ensures durability of resistance in wheat varieties. Spring wheat line CI14275 displayed high levels of field resistance to stem rust in Kenya and USA compared to the parents in its pedigree (Thatcher, Kenya Farmer & Lee). To understand the genetics of resistance in CI14275, 114 Recombinant Inbred lines (RILs) were developed from the cross CI14275/LMPG-6 and screened for seedling response to Pgt races TTTTF, TPMKC, TRTTF, TTKSK & RTQQC. Chi-square goodness of fit tests suggested one-gene, three-genes, and four-genes segregated for response to races TTTTF, TPMKC and RTQQC, respectively. The RILs were all susceptible to races TTKSK and TRTTF. CI14275 showed intermediate low infection types only against races TPMKC (23-) and TTTTF (1+3C). Field screening of the population was completed in Kenya, Ethiopia and St. Paul where CI14275 showed high levels of resistance TMR (Kenya), 5MS (Ethiopia) and 5RMR (St. Paul) against the prevalent races in the stem rust screening platforms. LMPG-6 displayed susceptible responses ranging from 70S-90S in the three locations. 90K wheat Single Nucleotide Polymorphism (SNP) marker platform will be used to genotype parents and the population.
Institute of Agriculture and Food Research and Technology
Karim Ammar, Susanne Dreisigacker, Josí María Arjona, Conxita Royo
Understanding the effect of genetic factors controlling flowering time is crucial to fine-tune crop adaptation to each target environment and maximize yield.
A set of spring durum wheat inbred lines carrying all but one of the possible allelic combinations at Ppd-A1 and Ppd-B1 genes was developed through a collaboration between IRTA and CIMMYT. The collection was grown during several years at four sites at latitudes ranging from 19?N to 41?N in order to assess the effect of Ppd-1 genes on development, biomass production and allocation, as well as grain yield formation.
Environmental constraints were responsible for most of the observed variation for flowering time and yield components. Latitude was a main driver of flowering time, which was later in northern sites and associated with lower minimum temperatures before flowering. Data on environmental constraints explaining a large proportion of grains m-2 and kernel weight variation will be presented. The effect on flowering time of Ppd-A1 alleles conferring photoperiod insensitivity was enhanced at sites with average daylength before flowering lower than 12h. Ppd-A1 caused a stronger effect on flowering time than Ppd-B1, which was found responsible for differences in grains m-2, associated with longer photoperiods from double-ridge to terminal spikelet stages. These differences in grains m-2, however, did not result in higher yields due to kernel weight compensation. Late flowering genotypes carrying alleles conferring photoperiod sensitivity had greater biomass at anthesis but it did not confer superior yields. Early flowering times were associated with higher yields in autumn-sowing sites due to a large contribution to yield of current photosynthesis during grain filling. Early flowering genotypes tended to yield more due to higher kernel weights, and the interaction of allele combination x environment will be discussed in the context of using allelic information as environment-specific guideline in breeding efforts.
National Institute of Agriculture Research, Tunisia
Meeting food security challenges is a high priority in many developing countries. North African countries are among those with the highest per capita wheat consumption in the world and chronic grain deficits. Climate change scenarios predict decrease of rainfall and increase of temperature with negative impact on crop production and hence food security. Along with adoption of modern technologies, breeding higher yielding and more climate change resilient wheat varieties is widely seen as a tool that can sustain past yield gains and food production increases. Durum wheat production in Tunisia greatly benefited from the green revolution ingredients. Continued breeding lead to replacement of the early semi dwarf varieties with higher yielding, better disease resistant and more drought tolerant ones that have positively impacted yield at farmer and national level. Monitoring gains from increased yield potential and resistance to the most damaging foliar diseases, mainly septoria leaf blotch, leaf rust and stripe rust, showed that grain yield of recently released varieties is up to four times that of the tall late maturing landraces grown before the 1970's and up to 2.5 times that of varieties of the early years of the green revolution. Chlorophyll content, green leaf duration, deeper root development from diverse donors including wild wheat relatives and grain yield are being integrated in the breeding program for the selection of more drought and heat stress tolerant durum cultivars
Yellow rust caused by Puccinia striiformis f.sp. tritici, is the most devastating fungal disease of wheat, especially in CWANA region. Growing cultivars with durable resistance is the most economical control measure. A field study was conducted to evaluate 500 bread wheat landraces along with the susceptible control ?Morocco? using artificial inoculation under field conditions at Tel Hadia, Syria during 2010-11 and 2011-12 growing seasons. The most prevailing yellow rust virulent race 70E214 was used for artificial inoculation. The disease scoring started when the disease severity was more than 50 % on the leaves of the susceptible check ?Morocco? and continued for four scorings at the intervals of 7 days. Slow rusting resistance was assessed based on the development of disease over time using the Area under Disease Progress Curve (AUDPC), Coefficient of Infection (CI), Final rust Severity (FRS), Infection Rate ?(r)? and Relative Resistance Index (RRI). None of the landraces showed immune reaction and 10% showed lowest values for all parameters, suggesting that resistance in these landraces was controlled by major genes. Approximately 65% of landraces were marked as having different levels of slow rusting and 25% were highly susceptible. Cluster analysis based on partial resistance parameters revealed two major clusters: Susceptible and low level of slow rusting were grouped in the first cluster; Resistant, high level and moderate level of partial resistance were grouped in the second cluster. By comparing the results obtained from RRI and others parameters, we found that landraces with very low values for all parameters exhibited high RRI value of 9, while those that showed high, moderate and low levels of slow rusting, had RRI ranges of 8-9, 7-8 and 5-7, respectively. The landraces with maximum values from each parameter showed very low RRI values of less than 5.
Crop Development Centre/Department of Plant Science, University of Saskatchewan, Saskatoon, Canada
Sajid Ali, Dinah Qutob, Steve Ambrose, Ron Maclachlan, Kun Lou, Curtis Pozniak, Yong-Bi Fu, Andrew Sharpe, Randy Kutcher
Puccinia striiformis f. sp. tritici (Pst), the cause of wheat stripe rust, is one of the most important pathogens of wheat. Attempts have been made in the past to characterize the worldwide genetic structure of Pst populations, excluding Canada. Characterization of 59 isolates identified 33 races with three most common races representing half of the population and subtle differences in races of eastern and western prairies. For molecular characterization, 48 isolates were sequenced to obtain SNPs and genotyped with Pst-specific SSR markers. Isolates that were suspected of recombination based on SNP data were examined for their telia production ability as a proxy for sexual recombination. The study revealed that the majority of the population was clonal, however, not exclusively clonal, with the existence of four genetic lineages. Two lineages previously reported were identified: PstS0, representing an old northwestern-European and PstS1, an invasive warmer-temperature adapted lineage. Additionally, two new lineages, PstPr and PstS1-related, were detected that have not been reported previously. The PstPr and PstS1-related lineages produced more telia than the other lineages and had double the number of unique recombination events compared to PstS0 and PstS1. PstPr was concluded to be a sexual recombinant and an exotic incursion, which was closely associated with PstS5, PstS7 (Warrior), and PstS8 (Kranich) lineages, all of which arose by sexual recombination in the center of diversity - the Himalayan region. The total phenotypic variation in the population could not be explained solely by molecular genotypes, and a hypothesis on existence of epigenetic machinery in the Pst genome was tested. Homologs of the DNMTases class (DNMT1) were identified, providing compelling evidence of a role for DNA methylation. As a first report of DNA methylation, an average of ~5%, 5-methyl cytosine (5-hmC) in the Puccinia epigenome indicated the possibility of epigenetic regulation, which merits further investigation.
Prashant,Vikram, Deepmala, Sehgal, Juan, Burgueno, Carolina, Sansaloni, Cynthia, Ortiz, Ernesto, Solis, Lulu, Ledesma, Pillar, Suaste, G, Fuentes, J, Ireta, A, Sharma, P, Srivastava, Sridhar, Bhavani, Thomas, Payne, V, Govindan
Wheat breeding programs have successfully harnessed the potential of elite germplasm pool and have contributed significantly to global food security. However, to obtain additional genetic gain, useful diversity for key traits from landraces, synthetics and wild relatives should be incorporated in breeding germplasm pool. Maladaptation and linkage drags are the bottlenecks in utilizing these exotic genepools for pre-breeding. A systematic, focused, large scale effort has been pursued at CIMMYT through a three-way cross (exotic x elite1 x elite2) population development strategy. Population was advanced through selected-bulk scheme in way to select relevant genetic diversity while maintaining large population sizes. A total of 984 advanced pre-breeding lines (PBLs) were evaluated in multiple environments for grain yield related traits, micronutrient content and diseases resistance (yellow rust, stem rust, powdery mildew, and karnal bunt). Potential useful lines for these traits have been identified. High-density genomic characterization of PBLs, parental elites and exotics was conducted through a "haplotype map" based approach, which revealed 16% (58/361) exotic specific haplotype block (HB) introgression in PBLs. Out of 58 exotic specific HBs, 12 (12/361 = 3%) were found associated with traits evaluated in the study. Three HBs, H1.28 (1A), H18.1 (6D) and H5.23 (2B) were significantly important as they showed consistent effects across environments for grain yield (1A and 6D) and yellow rust (2B). This significant contribution of exotics into PBLs opens avenues to mine and utilize their useful alleles in wheat improvement. This research describes systematic large-scale pre-breeding efforts, as proof of concept of exotic germplasm deployment to the breeding pipelines simultaneously enriching genetic knowledge through high-density genomics analysis. Genetic knowledge coupled with breeding efforts should provide substantial gain required for next generation wheat varietal improvement.
Department of Agriculture, Sunsari, Nepal
Wheat (Triticum aestivum L.) is one of the major cereal crops vital for global food supply. Most of the wheat crop in developing world including that of Nepal is either grown with limited irrigation or under rainfed conditions and thus face moisture stress at one or more growth stages limiting grain yield. An experiment was carried out at the Institute of Agriculture and Animal Science, Rampur to evaluate the genetic variability of selected drought adaptive traits in Nepalese wheat germplasm. The wheat genotypes evaluated comprised of Nepalese landraces and commercial cultivars, CIMMYT (International Center for Maize and Wheat Improvement) derived advanced introduction lines and three checks with differential drought adaptability. The wheat genotypes were grown in pots (single plant) arranged in a replicated split plot design in greenhouse under two contrasting moisture regimes, optimum and moisture stressed. The genotypes were evaluated for water use, water use efficiency, relative leaf water content and biomass production. The ANOVA (Analysis of Variance) revealed significant variation between environments and among the wheat genotypes for most of the traits studied. A wide range of variability was observed for water use, water use efficiency, biomass yield and relative leaf water content in moisture stressed and non-stressed environments. Nepalese cultivar Gautam showed a number of favorable drought adaptive traits, whereas, Bhrikuti was average in this respect. Based on the scores of drought adaptive traits recently released Cultivar (cv). Vijay was characterized as drought sensitive. A number of landraces and advanced breeding lines showed high level of water use efficiency and other positive traits for drought adaptation.
Lake Chad Research Institute, Maiduguri, Borno State-Nigeria
Dattijo Aminu, Zakari Goji Silas Turaki, Fatima Henkrar, Udupa Sripada
The research was conducted at ICARDA, Rabat. Twenty-four accessions were obtained from LCRI for marker analysis. Wizard Genomic DNA Purification Kit was used for DNA extraction. DNA was extracted by CTAB method and quantified using 1.0 % (w/v) agarose gels. Total of 12 loci, 5 functional and 7 linked random DNA markers to the traits of interest were used. PowerMarker and DARwin software were used to calculate the No. of alleles and values of genetic diversity, PIC, genetic distance, and NJ dendrogram. The total No. of detected alleles was 39; and mean No. of alleles was 3.25. No. of alleles range from 1 (Dreb-B1) to 9 (Xgwm577). Genetic diversity index ranged from 0.0000 in Dreb-B1 to 0.8471 in Xgwm577. The PIC value was also varied from 0.0000 (Dreb-B1) to 0.8296 (Xgwm577). The frequency of biotic resistance linked random DNA marker allele at Xgwm144 and Xwmc44, associated with yellow and leaf rust gene was 25% each. Marker alleles Xgwm577 and Xgwm533 linked to Stb2 and Stb8 at 150 and 120bp have frequencies of 21 and 4%. The frequency of abiotic resistance showed 50% of accessions had 1R segment (1BL.1RS translocation) and 58% of accessions showed presence of 120bp allele of Xwmc89, associated with QTL for drought tolerant. Functional marker alleles of Dreb-B1 associated with drought tolerant genes showed alleles frequency in all accessions. Linked marker allele Xgwm111 linked to heat tolerant gene showed 17% allele frequency at 220bp. Rht1 and Rht2, the allele frequencies were 92 and 4%. 92% of the cultivars had photoperiod insensitive allele at Ppd-D1 locus. VrnA1a and VrnA1c primer pair amplified at 965, 876, and 484bp, allele frequency of 13 and 87%. Cluster analysis had grouped the accessions into 5 at a genetic distance level 0.15.