University of Mohammed V/ICARDA
HAFSSA,KABBAJ, AYED, AL ABDALLAT, GREGOR, GORJANC, JESSE, POLAND, MIKAEL, MILOUDI NACHIT, AHMED, AMRI, BOUCHRA, BELKADI, KARIM, FILALI MALTOUF, FILIPPO, BASSI MARIA, , , , , , , , , , , ,
Durum wheat (Triticum durum Desf.) is a major stable crop and it represents a base of the Mediterranean diet. This region is subject to a Mediterranean climate, which is extremely unpredictable with severe changes in moisture and temperature occurring each crop season. This unpredictability is summarized by breeders as GxE and the identification of traits controlling this interaction is quintessential to ensure stability in production season after season. To study the genetics of yield stability, four RILs populations derived from elite x elite crosses were assessed for yield and 1,000-kernel weights across five diverging environments in Morocco and Lebanon. These 550 RILs were characterized with 4,909 polymorphic SNPs via genotyping by sequencing. A consensus map was derived by merging the individual genetic maps of each population. Finally, imputation was used to fill all the missing haplotypes and reach a reduction of missing data to below 8%. Several significant QTLs were identified to be linked to TKW, grain yield and a stability index, namely AMMI wide adaptation index (AWAI). A second approach to identify loci controlling stability was the use of a global panel of 288 elites, accessions and landraces tested in 15 diverging environment. Multi-locations data were compiled via GxE models to derive the AWAI stability index. In addition, this panel was characterized with 8,173 polymorphic SNPs via Axiom 35K array. Significant associations were identified for all traits, including QTLs unique to AWAI. The sum of the identified QTLs can now be pyramid via marker assisted selection and molecular designed crosses in order to obtain very stable cultivars.
Agharkar Research Institute Pune
yashavantha kumar,Kakanur, Shrikanth, Khairnar, Balgounda, Honrao, Vijendra, Baviskar, Ajit, Chavan, Vitthal, Gite, Deepak, Bankar, Sameer, Raskar, Satish chandra, Misra, , , , , , , , , , , ,
Heat stress globally remains the most important factor determining yield anomalies. Terminal heat stress shortens the duration of grain filling. Hence, this investigation was undertaken during the cropping season 2016-17 to evaluate heat stress tolerance of 32 bread wheat genotypes planted in timely (optimal temperature) and late (terminal heat stress) sown condition at Agharkar Research Institute, Pune. Data were collected and analyzed for various agronomical and physiological traits and also selection indices for stress tolerance, derived from grain yield of wheat genotypes under optimal and late sowing conditions. It was observed that the genotypes DBW 187, GW 477, HD 2932, DBW 107, PBW 752 were the highest yielding under timely sown condition whereas, HD 3226, DBW 187, HP 1963, HD 3219, DBW 196 were the highest yielding under late sown condition. DBW 187 was found to withstand the stress conditions. Minimum percent yield decrease and high yield stability index (YSI) was found in HD 3219 followed by HD 3226 and DBW 196 which indicated their better performance under stress condition. Harmonic mean, a stress tolerance selection index was found to be the best fit of linear model (R2 = 0.78) and a good indicator of high yield under heat stress condition. Physiological parameters, Chlorophyll (SPAD), canopy temperature (Infra-red thermometer) and vegetation index (NDVI) have not shown significant relation with yield, however, they were found to be significantly associated with yield contributing traits like biomass, thousand grain weight, grain number per spike. DBW 187 and HP 1963 showed stable yields with high PCA 1 and low PCA 2, indicating their resilience to stress conditions. The investigation has resulted in identification of genotypes for terminal heat stress conditions and also given greater insights in understanding the importance of physiological traits and stress tolerance indices in selection process.
University of Georgia
Mohamed,Mergoum, Yuanfeng, Hao, Jerry, Johnson, Dan, Bland, James, Buck, John, Youmans, Benzamin, Lopez, Steve, Sutton, Zhenbang, Chen, , , , , , , , , , , ,
Leaf rust disease, caused by the fungal pathogen Puccinia tritcina, is the most destructive foliar disease of wheat worldwide. Gene combination of Lr37/Yr17/Sr38 has been used in Georgia (GA) to prevent the loss from leaf rust; however, with the emergence of new virulent races, these genes have lost their effectiveness. 'AGS 2000' and 'Pioneer 26R61' are the most common soft red winter wheat (SRWW) cultivars in Southeastern US, and have been used as good sources of resistance to leaf and stripe rusts, and powdery mildew. To characterize the genetic basic of resistance of AGS 2000, a mapping population of 178 recombinant inbred lines (RIL) has been developed from a cross with Pioneer 26R61. This population was genotyped using a combination of SSR, DArT, and SNP markers, and a total of 2734 markers covering the entire genome were used for the construction of genetic map. Phenotypic evaluation of parents and RIL population was conducted at the seedling stage using a virulent GA leaf rust race. QTL mapping revealed a major QTL on chromosome 2BL, explaining about 20% of total phenotypic variation in AGS 2000. Additionally, a minor QTL was also detected on chromosome 5B. QTL on 2BL was identified as a novel gene, and can be used in marker-assisted selection for leaf rust resistance.
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.
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.
Chris K. Sørensen, Rodrigo Labouriau, Annemarie Justesen, Mogens Hovmøller
Host vernalisation and temperature strongly affect the susceptibility of winter crops to pathogenic fungi. However, how the interaction of these environmental factors influence host susceptibility to Puccinia striiformis, the yellow (stripe) rust fungus, is poorly understood. An experimental system was developed to examine the effect of vernalisation, temperature regime (standard; 18 day/12 night °C and low; 12 day/6 night °C) and plant growth (seedling and adult plant stages) on changes in susceptibility of agronomically important winter wheat and triticale genotypes to P. striiformis races ('Warrior' and 'Kranich') highly predominant in several European countries. Host genotypes exposed to prolonged periods of low temperature, termed vernalisation, reduced disease susceptibility on specific winter host genotypes, although its effect differed considerably by the temperature regime and the P. striiformis race deployed. The influence of vernalisation on host susceptibility was more apparent at low temperature for the 'Warrior' race and at standard temperature for the 'Kranich' race. Triticale genotypes inoculated with the 'Kranich' race were particularly affected by the influence of vernalisation and temperature regime by displaying a shift towards reduced susceptibility at standard temperature. The effect of plant growth stage, i.e., vernalised seedlings versus adult plants, was most evident for the 'Warrior' race at standard temperature and at low temperature for the 'Kranich' race by revealing a lower infection type at the adult plant stage. The research findings presented here contributed to a better understanding of the role of environmental factors in host susceptibility. This, in fact, will aid in the development of more efficient early-warning systems and disease management strategies to the yellow rust fungus and in the decision making for the deployment of winter wheat and triticale genotypes.
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.
Northwest A&F University
Dejun Han, Jia Guo, Manuel Spannagl, Jianhui Wu, Aizhong Cao, Peidu Chen, IWGSC, Lili Huang, Jun Guo, Klaus Mayer, Zhensheng, Kang
Wheat cultivation in many regions faces threats by devastating fungal infections. However, wheat cultivar 92R137 shows resistance to Puccinia striiformis infection. To isolate the stripe rust resistance gene Yr26, an integrated transcriptomic and comparative genomics approach was undertaken. Near-isogenic lines of wheat (carrying Yr26 or not) infected with two Puccinia striiformis f. sp. tritici (Pst) (Virulence or avirulence to Yr26) were analysed in a dual detailed time series RNA-seq study. The emerging IWGSC refseq v1.0 genome assembly sequence serves as a valuable template and was also used for comparative genomics studies of the gene candidate region with the genome sequences of close relatives and wheat progenitors. Using bulked segregant analysis (BSA) to identify polymorphic SNPs between parent and resistant DNA (R-bulk) and susceptible DNA (S-bulk), flanking markers for Yr26 were identified. These two markers were mapped to the Chinese spring reference genome sequence, spanning a region of about 250 kb. The synteny analysis of this candidate region in CS chr1B with chr1A, chr1D, Wild Emmer Wheat (Td_chr1A and Td_chr1B) and Barley (chr1H) identified three candidate Yr26 genes. To detect gene candidates a dual time series RNA-seq analysis was performed. Genes differently expressed between rust susceptible (NIL-S) host lines and rust resistant (NIL-R) lines, carrying the Yr26 candidate gene were analysed. Both lines were inoculated with Pst carrying different avirulence factors (Pst-CYR32 and Pst-V26), compatible or incompatible with the corresponding wheat lines. Differential gene expression analysis (DEG) between compatible and incompatible interaction revealed DEGs in the wheat genome and in the Pst genome. From a network analysis of both wheat and Pst genes, we inferred connected co-expressed modules. Resulting modules showed particular enrichments for disease resistance, defense response to fungus and cell wall components.
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.