La Trobe University
Antony Gendall, Hans Daetwyler, Matthew Hayden
Wheat stem (Sr), leaf (Lr) and stripe (Yr) rust pathogens are among the most destructive fungal diseases threatening global wheat production. We utilized 2300 wheat accession including worldwide landraces, cultivars, breeding materials and 341 synthetic accessions backcrossed with three widely grown Australian cultivars (Annuello, Yitpi and Correll) to investigate rust resistance under wide environmental conditions. The germplasm was genotyped with 90K SNP chip, and was phenotyped for two seasons in three different environments against Sr and Lr and in four different environments against Yr. Different environments for each trait showed significant correlation with mean r values of 0.53, 0.23 and 0.66 for Lr, Sr and Yr; respectively. Single-trait genome wide association (GWAS) revealed several environment-specific QTL and multi-environmental QTL distributed on all chromosomes except 6D. Multi-trait GWAS confirmed a cluster of Yr QTL on chromosome 3B (within 8.3 cM) as well as a QTL for Sr and Lr on chromosome 3D. Linkage disequilibrium and comparative mapping showed that at least three Yr QTL exists within the 3B cluster including the durable rust resistance gene Sr2/Yr30. The same region was effective against Sr resistance but did not pass the stringent significant threshold in two environments. The 3D QTL was found mainly in the synthetic germplasm with Annuello background which is known to carry the Ag. elongatum 3D translocation carrying Sr24/Lr24 resistance gene. Interestingly, estimating the SNP effect using BayesR method showed that the correlation among the highest 5% QTL effects across environments were lower than that for the small effect QTL with differences in r values of 0.25 and 0.2 for Lr and Yr respectively. These results indicate the importance of small effect QTL that cannot be captured using GWAS in achieving durable rust resistance. The detected QTL in this study are useful resources for improving bread wheat resistance to rust diseases.
Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India
Punam Singh Yadav, Ramesh Chand, Vinod Kumar Mishra, Uttam Kumar, Arun Kumar Joshi
The Sr2 gene has been used extensively in bread wheat improvement for durable stem rust resistance. Interestingly, the resistance of Sr2, associated with the pleotrophic gene Pbc expressed as pseudo-black chaff (PBC), is tightly linked with Yr30/Lr27/Pm genes conferring multiple disease resistance. The linkage map of chromosome 3BS revealed that Sr2 is 0.43cM away from lesion mimic (lm) locus. The RIL population (Yangmai#6 ? Sonalika) of 88 lines including parents where Sonalika carries Sr2 and lm while Yangmai#6 is deficient to both was evaluated for three years (2013-2016). The objective was to determine if this fragment is inherited as one unit and provides resistance to multiple diseases. Twenty four SSR markers distributed between 0.00 to 7.09cM on 3BS covering both Sr2 (5.57cM) and lm locus (6.0cM) were studied in the RIL population. Phenotyping was done for Sr2 associated PBC and lesion mimic along with disease severity for leaf rust, and spot blotch. Positive and significant correlations were observed between leaf stem rust resistance with Sr2 carrying PBC and lm. However, lines with lm either alone or with Sr2 (showing PBC) exhibited spot blotch susceptibility. The reverse situation does not hold not true where genotypes carrying Sr2 alone showed no correlation with spot blotch resistance. This indicates that the Sr2 complex is inherited as a single unit. Use of 24 SSR also suggest that Sr2 and lm loci are tightly linked and inherited together. The co-inheritance of Sr2 and lm ensures the stability and durability of rust resistance. However, the discouraging observation of spot blotch susceptibility due to lm gene suggests a limitation in achieving multiple disease resistance in environments where spot blotch is important. We identified two transgressive segregates in the population showing least expression of lm despite the presence of Sr2 and lm together.
Mohamed 5th University / ICARDA
Samir Alahmad, Ayed Al-Abdallat, Lee Hickey, Abdelkarim Filali-Maltouf, Bouchra Belkadi, Filippo Maria Bassi
Durum wheat (Triticum durum Desf.) is a major cereal crop grown globally. The terminal reduced moisture and heat occurring at the flowering phase are among the main constraints to its production. The molecular basis of tolerance to these threats remains mostly unknown. A subset of 100 genotypes derived from a collection of 384 accessions originating from different countries were investigated for their root growth and architecture under water-limited and well-watered treatments. Two protocols were used, "clear pot" for seminal root angle and "pasta strainer" for mature root angle evaluation. This study reveals that root architecture did not change depending on water treatment. A genotypic variation in root angle was found and two categories of root types were identified: genotypes with (i) superficial and (ii) deep rooting systems. In order to investigate the impact of each root type on yield, all genotypes were tested in the field at multiple locations and under different water regimes. The same set was also tested for heat tolerance in the field under rainfed conditions. Heat was imposed by placing a polytunnel at flowering time to raise the temperature of 10 degrees. The yield, thousand kernel weight and grain number per spike, were evaluated and compared to assess grain fertility, considered as a key trait of heat tolerance. The complete set was genotyped and a genome scan using 8173 SNPs markers developed by 35K Axiom array allowed to identify the genomic regions influencing drought and heat adaptation mechanisms. The pyramiding of this genomic regions could lead to an improved resilience to climate change and increase durum wheat productivity.
Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, India
Vinod Kumar Mishra, Uttam Kumar, Ramesh Chand, Akhilesh Mishra, Arun Joshi
Ug99 is a devastating race of Puccinia graminis f.sp. tritici possessing virulence against resistant genes Sr31 and Sr24. This race is highly adoptive and has spread quite rapidly with 13 known variants covering 13 different countries. For reducing the vulnerability of wheat in south Asia to the Ug99, breeding durable resistant varieties is important. India, second largest wheat producer, falls in the predicted pathway of Ug99. Most of the Indian germplasm possesses Sr31 and Sr24 in their background. HUW468, a well adopted variety of north eastern plains zone (NEPZ) of India, carries durable resistance gene Sr2. To strengthen it, a MABB program was initiated to introgressed two major genes (Sr50 and SrWeb) using a donor line PMBWIR4 from CIMMYT. The foreground selection was performed with Xgwm47 for SrWeb and IB267 for Sr50 followed by the background selection by using 128 polymorphic SSR markers covering all chromosomes. Backcross progenies of HUW468 were screened in the field condition by using of Pgt race 21A-2 at IARI, Regional Station, Indore located in the central India. Superior selected lines from BC2F4:5 generation was planted at three locations in India namely; Varanasi, Indore and Dharwad. HUW468-09-25-47-09 and HUW468-09-25-47-56 were selected from BC2F5 generation having Sr50 and SrWeb along with Sr2 gene, superior agronomic performance and with 93.5% and 92.7% genome recovery, respectively. These two lines also possess 6-10 % yield superiority over the recipient parent HUW468. These lines have been submitted for registration in NBPGR (National Bureau of Plant Genetic Resources), India.
Research Center of Agricultural and Development in Northwest Semi-arid regions of Tunisia
Afef,OTHMANI, Olfa, SLAMA-AYED, Hajer, SLIM-AMARA, Mongi, BEN YOUNES, , , , , , , , , , , , , , , , , , , , , ,
Eleven durum wheat (Triticum durum Desf.) genotypes were screened to select for drought-tolerance under in vitro immature embryos culture. Drought stress is induced by using five PEG concentrations (0, 200, 270, 295 and 310 g/l of PEG 6000). Results showed, for all studied traits, significant differences among PEG treatments and genotypes. In fact, increasing PEG concentration decreases relative growth rate, callus water content, relative water content, in vitro tolerance and relative tolerance. Biplot analysis indicated that the first two PCs (principal components 1 and 2) explain 70.5 % and showed that Karim, Mahmoudi and Om Rabiaa are respectively the most drought tolerant varieties tested, however, Ben Bechir, Maghrbi and Nasr were the most sensitive.
Department of Agroecology, Aarhus University, Denmark
Chris Khadgi,S?rensen, Annemarie Fejer, Justesen, Mogens St?vring, Hovm?ller, , , , , , , , , , , , , , , , , , , , , , , ,
Wheat yellow (stripe) rust is a recurrent problem throughout the world, and resistant varieties are an efficient means of managing the disease. Therefore, characterization of diverse sources of resistance is of prime importance for wheat breeding. The objective of the study was to investigate variation in host response in incompatible interactions conferred by different R-genes. Epifluorescence and confocal microscopic methods were utilized for histopathological investigation of six yellow rust R-genes (Yr1, Yr5, Yr6, Yr15, Yr17 and Yr27) in Avocet S background, with Avocet S as the control. Fungal colony size and area of hypersensitive response (HR) were assessed for each interaction at 4, 8 and 16 days post inoculation (dpi). The pattern for Avocet Yr15 was distinct, because HR arrested the pathogen very early and rapidly restricted pathogen growth. Avocet Yr1 and Avocet Yr5 showed a less rapid HR and restriction of pathogen growth, but most colonies were completely surrounded by HR at 8 and 16 dpi. In Avocet Yr6 the size of colonies and the extent of HR were highly variable with continuous change up to 16 dpi. More extensive pathogen growth was observed in Avocet Yr17 and Avocet Yr27, where HR induction was delayed, resulting in large intermingled colonies at 16 dpi. All interactions were clearly different from the susceptible control. Thus each R-gene produced a different temporal and spatial distribution of fungal colonies and HR response. Colony size distributions and HR response patterns are potential parameters for characterization of host resistances with different modes of action in wheat against Pst. The results also expand our comprehension of host resistance in wheat against P. striiformis.
Turkey-ICARDA Regional Cereal Rust Research Center (RCRRC), ICARDA, Menemen, Izmir, Turkey
Muhammad Massub Tehseen, Ezgi Kurtulus, Maha Al Ahmed, Ahmed Amri, Mariana Yazbek, Ali Shehadeh
In 2016 the bread wheat (BW) and durum wheat (DW) landrace accessions were evaluated against PstS2 and in 2017 against a mixture of PstS2 and warrior race in field inoculations at Izmir precision stripe rust phenotyping platform. Inoculation was carried out three times during seedling, tillering and booting stages using mixture of fresh spore and talcum powder. Adult-plant responses of tested accessions were recorded according to 0-9 scale once the flag leaf of the susceptible cultivar became fully susceptible. During 2016, out of 3319 BW accessions, 1135 (36%), 871 (28%) and 1133 (36%) were found resistant (1-3 scale), moderately resistant (4-6), and susceptible (7-9) to PstS2, respectively. Amongst the resistant accessions in 2016, 1043 (33%) remained resistant while 786 (25%) showed moderate resistant and 1310 (42%) became susceptible. In 2017, 43% of moderately resistant accessions showed susceptibility to warrior race and 57% remained resistant to moderately resistant. Within the susceptible accessions to PstS2 race in 2016, 22% showed resistance to the warrior race and the remaining were susceptible. In case of DW in 2016, 76% (553) of the accessions were resistant to PstS2, 23% (163) were moderately resistant and only 1% (7) were found susceptible. In 2017, 329 (46%) of the resistant accessions were found resistant, whereas 289 (40%) and 105 (15%) showed moderately resistance and susceptible reaction to Warrior race, respectively. The present data indicated that BW landraces were generally more susceptible to stripe rust than DWs. Susceptibility of both BW and DW accessions to Warrior race indicated that most likely some of the uncharacterized resistance genes which conferred resistance to PstS2 were ineffective against the warrior race. Sources of resistance to both races were identified in both BW and DW. Genetic architecture of identified sources of resistance in present study requires further investigations.
Wheat Research Institute, Ayub Agricultural Research Institute,Faisalabad,Pakistan
Mehvish,Makhdoom, Javed, Ahmad, Makhdoom, Hussain, Iqra, Ghafoor, , , , , , , , , , , , , , , , , , , , , ,
Wheat crop is facing immense losses each year owing to climate change, eventually being major threat to global food security. So, the objective of the present study was to screening of advance lines under drought and heat stress conditions. In following study, 30 advance lines of wheat along with four checks(Faislabad-08, Millat-11, Galaxy-13 and ujala16) with three treatments (heat, drought, normal) were tested for different morphological (days to heading, plant height, days to maturity, biomass,1000 grain weight and grain yield) and physiological (canopy temperature at vegetative & reproductive stage, NDVI vegetative & reproductive), parameters. Biplot analysis depicted that V2, V3, V8, V14, V19, V25, and V30 showed the highest OP vector for grain yield in drought environment. Whereas, under heat conditions, V3, V4, V5, V10, V11, and V12 displayed their maximum longest vector for grain yield. Correlation analysis depicted that grain yield had non-significant correlation with canopy temperature (vegetative stage), normalized difference vegetation index (vegetative stage) canopy temperature (reproductive stage), plant height, days to heading and days to maturity under heat stress environment, while it had significant association with biomass and thousand grain weight. Under drought environment, grain yield had positive and significant correlation with biomass while on the other hand it had negative but significant association with normalized difference vegetation index (reproductive stage) and canopy temperature (reproductive stage). Best performing lines could be efficiently exploited in research programs to evade the perilous impact of climate change.
Vegetable Research Institute AARI, Faisalabad, Pakistan.
Etlas,Amin, , , , , , , , , , , , , , , , , , , , , , , , , , , ,
In the present study five bread wheat genotypes (9797, 9801, 9802, Chakwal-50 and Chakwal-86) were tested in a 5?5 full diallel analysis for the estimation of combining ability for yield and its related traits. In randomized complete block design (RCBD) twenty F1s along with their parents were planted in field with three replications in the research area of Department of Plant Breeding and Genetics, University of Agriculture, during 2014-15. Plant height, No. of grains/spike, spike length, No. of productive tillers/plant, flag leaf area, No. of spikelets/spike, 1000 grain weight and grain yield per plant were studied. Except spike length mean squares due to GCA were highly significant for all the traits. All the characters showed highly significant mean squares for SCA and RCA. SCA variance was lower than GCA variance for number of grains/spike and spike length presenting the major role of additive gene action in the inheritance of these traits. While for plant height, flag leaf area, number of spikelets/spike, number of fertile tillers/plant, 1000 grain weight and grain yield/plant the value of GCA variance was lower than the value of SCA variance exhibiting non-additive gene action. Chakwal-50 was the best general combiner for plant height, spike length, number of spikelets/spike, number of grains/spike and grain yield/plant. The best specific combination for most of the traits was 9802?Chakwal-86. In future wheat breeding research programmes, good specific and general combiners can be exploited.
Plant Pathology Research Institute
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Leaf rust resistance genes Lr9 and Lr19 were previously highly effective against the most predominant races of Puccinia triticina in Egypt. In 2015/2016 growing season, susceptible field reaction was recorded on these two genes where rust severity reached about 40S for Lr9 and 5S for Lr19 under Egyptian field conditions at four locations i.e. El-Behira, El-Minufiya, El-Qalubiya and El-Fayom governorates. Eight leaf rust field samples were collected from these governorates (four from each of Lr9 and Lr19). Forty single isolates were derived from the collected samples of Lr9 and Lr19 (each with 20 isolates). Eight pathotypes were identified from Lr9 and only two pathotypes were identified from Lr19. The most frequent pathotypes virulent to Lr9 were KTSPT (30%) followed by TTTMS (25%). Moreover, the other pathotypes ranged from 5 to 10%. Whereas, the most frequent pathotype virulent to Lr19 was CTTTT (85%) and the lowest PKTST was 15%. Pathotypes i.e. PRSTT, NTKTS and TTTMS identified from Lr9 were more aggressive on most of the tested leaf rust monogenic lines, as they were virulent to 36, 35 and 35 lines, respectively from a total of 39 lines. The two pathotypes; PKTST and CTTTT identified from Lr19 were virulent to 36 and 35 lines, respectively. Moreover, leaf rust pathotypes i.e. NPTNK and PRSTT from Lr9 and PKTST from Lr19 were the most aggressive on the tested wheat cultivars at seedling stage. The Lr2a was the most effective leaf rust resistance genes against the tested pathotypes at adult plant stage. Wheat cultivars Misr 1, Misr 2 and Nubariya 1 were the most resistant cultivars against the tested pathotypes at adult plant stage.