ICAR NRC Plant Biotechnology
The present challenge in wheat breeding is to decipher the molecular mechanisms of heat stress response and thermotolerance in detail for future applications. Several reports indicate the ability of plants to maintain a memory of stress exposure throughout their ontogenesis and even transmit it faithfully to the following generation. Here, three diverse genotypes of wheat viz., HD2967, WR544 and C306 were used for thermotolerance assays. The genotype HD2967 was able to withstand heat stress regimes (37?C and 42?C, 2 hours). Harvested seeds were sown and further raised for two consecutive years and phonotypical data evaluated in natural field condition by exposing to heat stress during generative stages in a heat trap chamber. Maximum tiller numbers and flag leaf length were noticed in second generation plant of 37?C heat exposure whereas flag leaf width in second generation 42?C heat exposure relative to the untreated plant. Auricle length showed no difference but plant height was notably increased in the second year in all the heat exposed plants. In grain yield index, ear head length was greater in the second year and fluctuations in grain number was noticed among the heat treated plant with more yields in 42?C and 42?C HTHT in the second year. IRGA and SPAD recording showed high photosynthesis and chlorophyll content in 37?C HTHT. High modulation of transcripts of several genes involved in DNA methylation and heat stress were also observed. The domino effect of heat stress in earlier generation, in this transgenerational analysis, points towards a probable epigenetic effect. Further studies are in progress to confirm and clarify the mechanisms for future manipulation in breeding for thermotolerance.
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.
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.
National Research Centre
Food crisis is a major concern in Egypt, where drought and saline soils are ubiquitous. Wheat is a staple food in Egypt, which is only moderately tolerant to drought and salinity. Due to its rapidly increasing demand, there is an urgent need in Egypt to enhance wheat yields under drought and salinity conditions. Improving salinity or/and drought tolerance of genotypes is inhibited by a lack of efficient evaluation methods. High throughput precision phenotyping provides an innovative technology to screen for enhanced salt or drought tolerance from a large of number of genotypes under field conditions and can have immediate value to plant breeding. Therefore, we have tested several wheat phenotyping techniques i.e., canopy temperature (CT), spectral reflectance (SR), chlorophyll content (SPAD value), crop ground cover, relative water content (RWC), Water soluble carbohydrates (WSC), leaf area index (LAI), crop morphological traits, and grain wheat yield and yield components. We documented strong correlation/linear regression/polynomial regression between the wheat phenotyping techniques and in-season biomass/grain yield. It could be concluded that the documented results confirmed that several landraces were selected as drought/salinity tolerant out of 762 wheat landraces wheat were screened. Using high throughput precision phenotyping could provide an innovative technology and can have immediate value to plant breeding.
North Dakota State University
The rapid adoption of new varieties of wheat with disease resistance is critical to mitigating losses due to new diseases or disease races, even when only part of an integrated disease management program may include fungicides. There are numerous sources of information that can be used by farmers in North Dakota when selecting varieties with specific disease resistance as well as other traits. Formal surveys were conducted to determine the role of extension activities on the adoption of Fusarium Head Blight (FHB) control practices especially on the use of new varieties with FHB resistance. This disease became a regular and devastating problem of small grains in eastern North Dakotas in the 1990s. In a survey specific to North Dakota conducted in 2010, most respondents indicated that information from the extension service was their main source of information for FHB control with varietal selection their primary means of control. Extension publications, accessed through the internet or as hard copy obtained from an extension office or at an extension meeting were the most important sources; fewer respondents obtain their information from extension meetings and field days. A survey conducted in 2014 found that private sources (consultants and input suppliers) are becoming more important sources of information for FHB control and varietal selection, perhaps because the disease has become better understood and most new varieties have some level of FHB resistance. In durum wheat, where there are few varieties available from the private sector, extension publications were found to be the main source of information used for selecting new varieties. Data from these surveys show the importance of a strong and active extension program in ensuring that new varieties with resistance to new diseases/disease races are readily adopted.
Wheat Research Institute, Ayub Agricultural Research Institute,Faisalabad,Pakistan
Javed Ahmad, Ghulam Mehboob Subhani, Makhdoom Hussain
Crops vary greatly in their tolerance to heat stress. Among the major staples wheat is considered the most sensitive. Wheat production is severely threatened in many countries by heat stress especially during reproductive and grain-filling stages. For recent decades due to change in global climate, the qualitative and quantitative yield of wheat is affected. To meet the demand of food requirements of ever increasing population there is a need to develop varieties which can tolerate heat stress for which screening of germplasm is pre requisite. In the present study, 30 genotypes were used to check their response to heat stress using randomized complete block design following two different sowing dates. Analysis of variance and multivariate analysis were used for finding important traits and best genotypes in relation to heat stress. High broad sense heritability coupled with high genetic advance was measured for gluten and zeleny indicating the presence of additive gene effect for these traits. Principal component analysis showed that under heat stress conditions genotype 11, 14, 15, 20 and 30 performed well. These genotypes were also found resistant to yellow and brown rust and can be used in further breeding programs for development of heat tolerant, rust resistant genotypes.
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.
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.
USDA-ARS, Pullman, WA, USA
Lu Liu, Meinan Wang, Junyan Feng, Deven See, Shiaoman Chao
Stripe rust, caused by Puccinia striiformis f. sp. tritici, is the most destructive disease of wheat in the US Pacific Northwest. Durable high-temperature adult-plant (HTAP) resistance to stripe rust has been emphasized for breeding wheat cultivars and the resistance level has been gradually increased since the early 1960s. Wheat cultivar Madsen has been widely grown, intensively used in breeding programs, and has exhibited durable and high level resistance to stripe rust since its release in 1988. To map its resistance genes and determine the genetic basis of durable and high-level of resistance, Madsen was crossed with susceptible cultivar Avocet S, and 156 recombinant inbred lines (RILs) were developed. The RILs and parents were tested with races PSTv-37 and PSTv-40 in seedling stage at low temperatures in the greenhouse and in adult-plant stage in the fields of Pullman and Mount Vernon, WA in 2015 and 2016 under natural infection of the pathogen. The RILs were genotyped with single-nucleotide polymorphism (SNP) markers derived from genotyping by sequencing and the 90K Illumina iSelect wheat SNP chip. A linkage map was constructed with 1,348 SNP loci. QTL analysis identified three genes for all-stage resistance on chromosomes 1AS (QYrMad.wgp-1AS), 1BS (QYrMad.wgp-1BS), and 2AS (QYrMad.wgp-2AS); and two QTL for HTAP resistance on 3B (QYrMad.wgp-3B) and 6B (QYrMad.wgp-6B). QYrMad.wgp-2AS was the most significant QTL, explaining 16.03-71.23% phenotypic variation depending upon the race or environment, followed by QYrMad.wgp-6B that was consistently detected in all field experiments and explained 6.7-35.9% of the phenotypic variations. Based on the chromosomal locations and the results from other studies, QYrMad.wgp-2AS contains Yr17 and a HTAP resistance QTL, and QYrMad.wgp-1AS is a new QTL. The interactions among these QTL were mostly additive. The combination of the five QTL for different types of resistance provides the durable and high level resistance to stripe rust.
University of the Free State and Seed-Co
Vicky Coetzee, Cornelia M. Bender, Renée Prins, Zacharias A. Pretorius
Notwithstanding the re-emergence and importance of wheat stem rust caused by Puccinia graminis f. sp. tritici (Pgt), the degree of protection provided by different types of resistance has not been carefully investigated in contemporary studies. Seven wheat entries were exposed to stem rust infection and fungicide response in a split-plot field experiment over two seasons. Severe epidemics of Pgt race PTKST, generated by frequent inoculation of spreader rows within and around the trial, developed in both years. By comparing grain yield in rusted and fungicide sprayed plots, varieties SC Nduna (Sr31) and SC Stallion (Sr2+Sr31) sustained mean yield losses of 28.8% and 20.7%, respectively. From entries with adult plant resistance (APR), Kingbird recorded a loss of 10.1% as compared to W1406 (19.5%) and W6979 (15.4%). Grain yield of SC Sky which exhibits all stage resistance (ASR) was reduced by 6.4% over the two seasons. The highest yield loss (47.9%) was measured for Line 37, the susceptible control. A significant linear relationship occurred between percentage yield loss and AUDPC in both seasons (R2=0.99 and 0.83). This study showed that not all sources of APR to stem rust provided the same level of protection under severe disease pressure. In the absence of virulence for SC Sky, ASR conferred the most protection.