Department of Plant Molecular Biology, University of Delhi South Campus
The flag leaf and spike are the prime organs in wheat (Triticum aestivum L.) which contribute majorly for spike photosynthesis and eventually aid in grain filling. In this study we have tried to elucidate the effect of abiotic stress on the grain filling and spike photosynthesis. In order to unravel the role of flag leaf, awn, and spike in wheat grain filling and spike photosynthesis, 1000-kernel weight were calculated after removing flag leaves, awns, and by shading the spike in four wheat genotypes (PBW343, C306, K7903, HD2329) for two seasons (2014-2015, 2015-2016). A significant decrease in the grain filling was observed for all the genotypes. These results indicate the role of these organs in spike photosynthesis. The role of the awn tissue was investigated in PBW343 for its role in spike photosynthesis during heat stress. Deep transcriptome sequencing of the awn tissue (PBW343) was performed and it revealed 147573 unigenes. Out of these, 394 genes were differentially expressed genes (DEGs). These DEGs constitutes 201 upregulated and 193 downregulated genes. Genes involved in photosynthesis (Ribulose bisphosphate carboxylase/oxygenase activase B, NADH dehydrogenase, Fe-S protein2), membrane integrity (ATP-dependent zinc metalloprotease FTSH6), and ion channel transporters (two-pore potassium channel3) were prominently expressed. Gene Ontology (GO) enrichment analysis represents PSII associated light-harvesting complex II catabolism, chloroplast organization, photosynthesis light harvesting in photosystemI, ethylene biosynthesis, regulation of oxidoreductase activity, stomatal closure, chlorophyll biosynthesis categories, which are highly overrepresented under heat stress conditions. Therefore, utilizing the awn transcriptome information, Rubisco activase (RCA) gene was chosen for overexpression studies in wheat and rice with the aim to enhance the photosynthetic efficiency of the spike tissue leading to higher grain filling.
National Agronomic Research Institute of Algeria
Among the many biotic constraints to wheat production in Algeria, rusts and in particular yellow rust (Puccinia striiformis), are among the most prevalent diseases that occur mostly all over the northern part of the country. Yellow rust has become now sporadic due to the exploitation of effective resistant genes in different forms and combinations (from CIMMYT and ICARDA). Earlier, durable resistance was probably due to many genes, such Yr18, Yr9, Yr27 and Yr1.
Yellow rust appeared as epidemic in 2004, over 600 000 ha of bread wheat ; severity exceeded 70%. Yields from affected fields of Hidhab a susceptible variety did not exceed 5.2 q/ha, while resistant cultivars yielded up to 48 q/ha. Monitoring of the pathogen virulence factors and their changes provides basic information for the development of an early warning system. This experiment was carried out in 5 Eastern Algeria locations. 30 lines of a standard set of yellow rust and 14 near-isogenic lines from ICARDA were sown in 2-m rows in 2014 and 2015. According to the results, virulence on Heines Kolben (Yr2), Kalyansona (Yr2), Lee (Yr7), Avocet R (YrA), Federation*4/Kavkaz (Yr9), Yr6/6*Avocet ?S?, Yr7/6*Avocet ?S?, Yr9/6*Avocet "S", Yr17/6*Avocet "S", TP1295 (Yr25) and YrSU was common during those two seasons. The frequency of virulence on plants with Yr2, Yr6, Yr7, Yr9 or YrA and Yr27 was up to 80%. No virulence was observed on plants with Yr1, Yr3, Yr4, Yr5, Yr8, Yr10, Yr15 and Yr18 genes. This material was extensively used in our breeding programs and several new cultivars are in the on farm trials where a participatory selection approach is used. All resistant and performing new varieties are being spread for replacement of most old susceptible ones.
Abd El Badia
Wheat Disease Research Department
Mohamed Abdalla, Sobhy Negm, Adel Hagras
This work was carried out to study the response of five bread and two durum wheat cultivars to stem rust and its effect on grain yield under field conditions at Sids and Beni Sweif stations during the three growing seasons 2011/2012, 2012/2013 and 2013/2014. The loss in grain yield and kernel weight of the different wheat genotypes was variable according to the varietal response. Grain yield and kernel weight of the protected plots (protected by the effective fungicide Sumi-eight 5EC(CE)-1-(2,4-dichlorophenyl)1-4,4-dimethyl1-2-(1,2,4-triazol-y1)Pent -1-en -3-0L) at the rate of 70cm /200litter water per Fadden ) of all wheat genotypes were higher than the infected ones. Significant differences were found between infected and protected wheat genotypes.. Disease severity was recorded weekly to estimate area under disease progress curve (AUDPC). The AUDPC ranged from 85.33 to 405.00 (Sids 1 and Sohag 3) during 2011/2012, from 181.66 to 805.00 (Shandwel 1 and Sohag 3) during 2012/2013, and from 142.33 to 585.00 (Shandwel 1 and Sohag 3) during 2013/2014. Losses in kernel weight ranged from 3.39% to 31.03% (Sids 1 and Misr 1) during 2011/2012, from 9.79% to 44.18% (Sids 1 and Sohag 3) during 2012/2013,and from 5.67% to 26.86% (Sids 1 and Sohag 3) during 2013/2014. Yield losses ranged from 5.70% to 37.52% (Shandwel 1 and Misr 1) during 2011/2012, from 7.75% to 45.78% (Shandwel 1 and Misr 1) during 2012/2013, and from 7.14% to 30.59% (Sids 1 and Sohag 3) during 2013/2014. Yield losses correlated strongly with AUDPC. The results of this study indicate that bread wheat cultivars are (Giza 168,Sakha 93, Sids 1, Misr 1, Misr 2 and Shandwel 1) and Durum wheat are ( Beni Sweif 5 and Sohag 3) more tolerant than durum wheat cultivars. The Egyptian bread wheat cultivars Sids 1 and Shandawel 1 are more tolerant than the other bread wheat cultivars.
Agriculture and Agri-Food Canada, Lethbridge, Alberta
Gurcharn Brar, Randy Kutcher, Raman Dhariwal
Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat in western Canada. Although stripe rust was an issue in southern Alberta for many years, it became important in other parts of the country after a dramatic population shift in 2000, resulting from an invasive race. Sporadic epidemics of the disease are common and cause considerable loss, due to which, an intermediate level of resistance to stripe rust was required for new varietal registrations beginning 2017. Virulence surveys are of key importance in germplasm and cultivar development as they provide breeders and pathologists the information needed to better understand host-pathogen interactions and the effectiveness of Yr genes. Virulence characterization revealed a wide range of virulence phenotypes exhibited by 33 Pst races in western Canada, although only 2-3 races were predominant. The expression of Yr genes may differ between controlled conditions and natural field conditions as previously reported. Thus, stripe rust differentials and wheat cultivars grown in western Canada are also screened at multiple locations in every year. At present, all stage resistance genes Yr1, Yr4, Yr5, Yr15, Yr76, and YrSP are effective against the predominant Pst races, whereas at the adult stage under field conditions, Yr2, Yr17, Yr28, or those carried by Yamhill are also effective. Seedling resistance genes Yr7, Yr10, Yr17, or Yr27 were the most common in Canadian wheat cultivars. Of these, only Yr17 is effective under field conditions. Adult plant resistance genes Yr18 and Yr29 are carried by many cultivars, but are not effective under high disease pressure. The effectiveness of each resistance gene may vary between the eastern and western prairies of western Canada due to differences in virulence. Regular virulence surveys using contemporary and regional cultivars facilitate the development of rust resistant cultivars.
Department of Botany, Faculty of Biology, Government College Murree, Pakistan
Barkat Ali, Muhammad Fayyaz, Atiq ur Reman Rattu, Abdul Samad Mumtaz, Muhammad Imtiaz
The new arrival of wheat rust pathotypes through migration during wheat cropping season requires regular monitoring to secure wheat production. In the present study, we collected leaf rust (Puccinia triticina Eriks.) infected wheat leaves from three major wheat growing provinces of Pakistan in the year 2014 to assess the haplotype diversity of P. triticina (Pt) isolates. The rDNA ITS sequence data of collected isolates was used in NCBI BLAST analysis. The blast hits showed best matches with Pt accessions EU014050 (Iran), JN120331 (Iran), JX533577 (Iran), AY956549 (Iran), DQ417412 (Czech Republic), DQ417418 (Israel), DQ417413 (Slovakia) and AF511083 (Louisiana). However, in cluster analysis, the Pakistani isolates showed strong bootstrap support with only Iranian and Indian (races 77-5 & 104-4) accessions that indicated eastward migratory mode of Pt pathotypes in Pakistan through westerly wind patterns. The predominant genotype DQ417412 (similar in alignment with AY956549 from Iran) overcome the resistance of top Pakistan mega varieties Seher06, Inqilab91, Kiran95, SKD1, TJ83 and NIFA-Batoor. Hence, the ITS based information remains a rapid molecular tool for pathogen surveillance across countries and continents.
Kenya Agricultural and Livestock Research Organization
Ruth Wanyera, Bernard Otukho, Bernice Waweru, Hellen Wairimu, Sridhar Bhavani
Emergence of Pgt race Ug99 and rapid proliferation of lineal highly virulent races imminently threaten Kenyan wheat. Devastating epidemics have led to huge losses among smallholder farmers who invariably are unable to spray appropriately and in situations where susceptible varieties are grown. To combat stem rust, the Kenya wheat improvement program seeks to release high yielding stable genotypes with suitable levels of disease resistance. Moreover, detection of genotypes that are adapted to rain-fed environments is an overarching objective. Six hundred and seventeen genotypes from various CIMMYT nurseries (PCBW, EPCBW, PCHPLUS, and 9th SRRSN) were selected based on plant type and reaction to stem rust at Njoro. The reconstituted nursery-KSRON, was sown in the main season of 2016 at Njoro and Timau for further evaluation. Forty red grained lines depicting R-MR infection types, severity of 30% or less, and average Thousand Kernel Weight of >40g were then selected to constitute a yield trial. At each of eight diverse environments, trials also comprising four commercial varieties as checks, were designed in RCBD, three replicates laid out in contiguous array of 8 rows x 10 m plots. Genotype (G), Environment (E) and GE interactions effects were estimated by fitting the AMMI model to yield data, supported by a biplot visualization of the results. Analysis revealed significant (P ?0.01) genotype (G), environment (E), and GE interactions. The first three principal components (PC) explained ~78% of the observed variation. Environment was the predominant source contributing over 85% to total sum of squares. The biplot pointed to at least four environments that were highly correlated. By classifying genotypes based on Shukla's stability variance and Kang's stability rating, six genotypes (R1402, R1411, R1424, R1481, R1484, and R1486) were deemed high yielding and stable, and thus suitable candidates for further testing through the release pipeline.
National Institute of Agronomy of Tunisia, INAT
Maroua Ouaja, Hanen Sbei, Bochra Bahri
Septoria tritici blotch (STB) caused by the fungal pathogen Mycosphaerella graminicola (anamorph: Zymoseptoria tritici) is one of the most important foliar diseases of durum wheat (Triticum turgidum ssp. durum) in Tunisia. It attacks plants from seedling stages to maturity causing serious yield losses. Breeding for resistance to STB in durum wheat can provide an effective, economic and environmentally-safe strategy to reduce yield losses. However, this is hampered by lack of sources of resistance. In this context, a collection of 420 accessions of durum wheat from the National Bank of Gene (BNG) were evaluated for resistance to two virulent isolates of Z. tritici, namely TunBz-1 (across two environments) and TM220 (across one environment) under field conditions at three different development stages. The evaluation scale was ranged from 0% (immune plant) to 100% (100% of leave covered with symptoms). Three effects were studied on the collection: environmental effect E1-E2 (years 2016-2017), isolate effect I1-I2 (TunBz-1 and TM220) and physiological stage effect S1-S2 (seedling and adult). Results highlighted different sources of resistance between both seedling and adult stages. Moreover, 51 and 67 accessions have differential response to the two studied isolates respectively in seedling and adult stage. Furthermore, the Venn diagram has identified 23 accessions in the collection that are resistant to both isolates at both stages and that resistance was stable across environments. These accessions are located mainly in the center of Tunisia. Resistance to isolate TunBz-1 is expressed since seedling stage and there is stability of this resistance throughout the environments. The center of Tunisia seems to be a diversity center that includes different sources of resistance to STB. This collection could be the subject of a genome-wide association study (GWAS) as it presents different types of STB resistance categories that can be targeted via SNPs.
Hawassa Agriculture Research Centre
Agdew Bekele, Waga Mazengia, Shimekt Maru
Shortage of seed of rust resistant varieties is a challenge of small holder farmers in wheat production. To successfully address this issue, one of the essential elements in wheat production system is farmer's access to quality seed of improved varieties. This paper presents the experience of on-farm basic and pre-basic seed production of newly released rust resistant wheat varieties. For the first time in the country, On-Farm basic and pre-basic seed production of wheat varieties was carried out in two districts/woredas (Silti and Soddo) of two specific locations (Loke faka and Wacho) where the Edget Farmers' Seed Multiplier and Marketing Union was licensed to produce some crop varieties (cereals and pulse), beginning in the 2011/2012 cropping season. Model farmers from primary cooperatives were selected based on the past experience they had with the union in producing certified seed. Selected farmers and relevant experts were trained on how earh seed of wheat is produced. Accordingly seed multiplication of four wheat varieties was conducted with frequent monitoring and evaluation at the course of multiplication.
As a result sufficient and quality basic seed of newly released wheat varieties was produced on-farm in both Loke and Wacho locations for own utilization and seed market. The result of the experiment revealed that it was possible to multiply quality wheat seed provided that partnership (with GOs and/or NGOs) is well-built and cooperative farmers do farm management practices as per the recommendations. On-farm seed production can be sustainable if the strong partnership exists among stakeholders, and wheat seed growers are given premium prices for their seed which is supported by the legal frame work that encourages the seed production of early generations. More importantly, the result of this experiment has a useful implication on government policies and strategies and government institutions' practice on farm early seed generation production and marketing.
University of the Free State
Liezel Herselman, Botma Visser, Willem Boshoff, Zacharias Pretorius
Most South African winter wheat varieties display all stage resistance (ASR) to stem rust caused by Puccinia graminis f. sp. tritici (Pgt). To study inheritance, four resistant varieties were crossed to a susceptible parent (Line 37) and F2 populations were phenotyped at the seedling stage with stem rust race PTKST (Ug99 lineage). Populations derived from varieties Koonap, Komati, Limpopo and SST 387 segregated in a 3:1 ratio, indicating that a single, dominant gene confers resistance in each population. Assessment of F2 seedlings of four intercrosses between these varieties failed to deliver susceptible segregants therefore suggesting that they carry the same resistance gene. Genotyping of F2 plants with microsatellite markers produced consistent linkage of resistance with markers on chromosome 6DS. Experiments are underway to determine the relationship between resistance in the four winter wheat varieties and resistance genes Sr42, SrCad and SrTmp, all located on 6DS. Current evidence shows that ASR in the South African winter wheat varieties Koonap, Komati, Limpopo and SST 387 is based on a single gene and thus vulnerable to pathogenic adaptation in Pgt.
University Mentouri of Constantine, Algeria
Wheat is the world's most widely grown food crop. New races of pathogens frequently overcome current resistant varieties. To address this issue Algeria has strategies for immediate action, medium term protection and long-term research efforts to develop new resistant wheat varieties. Yellow rust is a very important disease of wheat in Algeria where 60% of the wheat crop is grown under cooler high elevation climate conditions (2?C ? 15?C). Crop losses reached 80% during the 2004/2005 epidemics. Strategies adopted to reduce the risk of wheat rust are ongoing yearly surveillance, awareness, and early warning systems to farmers; and breeding and developing new varieties with high yield potential and durable resistance. Several highly resistant varieties (Tiddis, Boumerzoug, Massine, Akhamokh and Yacine) were selected and promoted following seed multiplication and commercial release. They are also widely used in crosses to improve local varieties. The newly released varieties are being distributed to farmers that grow susceptible varieties. This gene deployment will provide a natural barrier between eastern to western Algeria to intercept the major direction of air flow. Fungicide control is now routinely applied soon after rust detection or even preemptively. The level of awareness for wheat rusts across Algeria is now very high. Training among farmers for visual detection is widely promoted by plant protection and extension services. These strategies have been very effective in mitigating the threat of wheat stripe rust such that losses have not exceeded 10% over the last five years.