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.
University of Sydney Plant Breeding Institute
Naeela Qureshi, Vallence Nsaiyera, Pakeer Kandiah, Mesfin Gesesse, Mandeep Randhawa, Mumta Chhetri, Bosco Chenayek, James Kolmer, Miroslav Valarik, Zaroslav Dolezel, Beat Keller, Matthew Hayden, Justin Faris, Harbans Bariana, Vanessa Wells
Dr. Norman Borlaug stated that rust never sleeps and this enables rust pathogens to produce new strains capable of putting rust resistance genes to rest. These pathogens continue to pose threats to global wheat production. Wheat breeders have made significant progress to control rust outbreaks using conventional selection technologies; however, some critical shifts in pathogen populations have let them down. Rapid evolution in molecular marker technologies in the last 15 years and refinement of phenomic facilities have expedited the process of discovery and characterisation of rust resistance genes to underpin the development and validation of markers closely linked with genetically diverse sources of resistance. A high proportion of the formally named rust resistance genes were characterized in the 21st century and markers closely linked with these genes have been developed and validated. The marker tagged sources of resistance to three rust diseases have equipped the wheat breeding community with tools to deploy combinations of all stage and adult plant resistance genes in future wheat cultivars. The question that whether we have enough resistance genes discovered to compete against the ever-awake rust pathogens. In our opinion, we cannot be complacent and discovery needs to continue to ensure food security. This presentation will discuss the role of advances in phenomic and genomic technologies to achieve durable rust control in wheat.
Kenya Agricultural and Livestock Research Organization
Hanningtone,Wanga, Phelister, Kinyanjui, Sridhar, Bhavani, Thomas, Fetch, , , , , , , , , , , , , , , , , , , , , ,
In 2016 rust surveys were carried out in all the four key wheat growing regions: South Rift (June, July), Mount Kenya (July), North Rift (September) and Central Rift (part of August and September). A total of 304 farms were sampled. Stem rust was detected in 235 (78.3%), yellow rust in twenty-eight (9.3%) and leaf rust in fourteen (4.7%) of the farms. Stem and yellow rust were detected in all the wheat growing regions while leaf rust was detected in South, North and Central Rift. Stem rust infection ranged from TR to 90S with maximum infection in Central Rift (88.3%), Mt. Kenya region (80.3%); South Rift (76.5%) and North Rift (72.4%). Yellow rust infection ranged TR to 60S with maximum infection in Central Rift (16.7%); North Rift(13.3 %) and minimum infection in South Rift( 4.9%),) and Mt. Kenya region ( 1.7%). Leaf rust infection ranged from trace to 50S with maximum infection in North Rift (10.2%) minimum infection in Central Rift (3.3 %) and South Rift (1.2%). Fifty percent of the eight previously released wheat varieties are now susceptible to the Ug99 race. Race analysis results from AAFC Canada suggested the presence of TTKSK which was dominating in North Rift and TTKSK, TTKST and TTTTF were dominant in the screening nursery at Njoro. Yellow rust in the region has increased in the current year owing to the incursion of a probable new race AF2012 which has resulted in increased disease severity on varieties and materials tested in the International nurseries at KALRO, Njoro.
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.
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.
CIMMYT International, South Asia, Regional Office, Kathmandu
Gurbinder Gill, Madan Bhatta, Andrew McDonald, Arun Joshi
The experience of seed system development works in Nepal shows that lack of business orientation is one of the key challenges for the growth of Nepalese seed enterprises (SEs). We implemented a business mentorship activity focusing on SEs in the project - Cereal System Initiative for South Asia. The business mentoring (BM) was implemented covering 10 SEs during 2014 to 2017 using discovery sensitization and facilitation mode. The key actions were, SWOT analysis, mentorship to develop strategic business plan, technical facilitation for seed quality improvement through maintenance breeding and on-farm farmer participatory trials as well as large plot demonstrations of recently released and pre-released wheat varieties. This resulted in 45% average increase in the volume of seed sold by individual SEs in three years. Five SEs started maintenance breeding in wheat and by third year, over 50% of the seed sold by the enterprises consisted of newly released varieties compared to 20% before mentoring. The improved performance of SEs prompted seed quality control authority of Nepal to issue a license to two of these private seed companies for maintenance breeding cum foundation seed production. As a consequence, foundation seed production of these entities increased by 60% in three years, and two of them have also started maintenance breeding in rice from 2017. The facilitation in developing business plan by SEs helped them to attract financial resources from different sources in upgrading seed processing, storage and laboratory facilities. Moreover, the National Wheat Research Program of Nepal has proposed the release of a new wheat variety BL 4341 through integration of on-farm trials and seed production data of these SEs. This new variety is resistant to major diseases, yields 7% higher than the popular cultivar NL 297 which was released 32 years ago and needed replacement due to susceptibility to wheat rusts
Crop Diseases Research Institute, National Agricultural Research Center, Park Road Islamabad, Pakistan
Anjum Munir, Khalil Ahmed Khanzad, Javed Iqbal Mirza, Shahzad Asad, Atiq ur Rehman Rattu, Muahmmad Imtiaz
Evaluation of candidate lines to develop resistant varieties at multiplications in Pakistan is a regular activity which has been successfully done for many years. This approach assists in generation of future resistant cultivars around appropriate genes combinations thereby providing durable resistance outputs for wheat productivity. This year, National Uniform Wheat Yield Trial (NUWYT) comprised of 60 candidate lines. Among these 15 lines were also present in the last years NUWYT. The two years data revealed that there was only one line V-12066 resistant to all three rusts during the two consecutive seasons 2015-16 and 2016-17. Four candidate lines NR-487, V-122557, PR-115 and NRL-1123 were found resistant to yellow and leaf rust during 2015-16 and 2016-17. A candidate line DN-111 was found resistant to leaf and stem rust. There were three lines NW-1-8183-8, NW-5-20-1 and MSH which were found resistant to leaf rust only during two consecutive seasons. Similarly, two candidate lines V-122559 and QS-3 were found resistant to stem rust only, while one line NR-443 was resistant to yellow rust only. The present study provide the screening and evaluation system of Pakistan for promoting and releasing the resistant wheat varieties.
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.
Khaoula El Hassouni, Priyanka Gupta, Hafssa Kabbaj, Meryam Zaim, Amadou Tidiane Sall, Bouchra Belkadi, Ayed Al-Abdallat, Ahmed Amri, Rodomiro Ortiz, Michael Baum
Durum wheat is the tenth most important crop in the world, but its cultivation is mostly limited to harsh, arid, and heat prone marginal lands. Breeding for tolerance to these conditions is often considered the most strategic approach to ensure adaptation, especially when paired with best agronomical practices. The word 'adaptation' summarizes all the research efforts conducted to identify the many traits controlling the mechanisms for withstanding or escaping the traceries of the environment. It can be summarized as "GGE vs E". The durum wheat breeding program of ICARDA deploys targeted phenotyping methods in combination with genomic scans to dissect these 'adaptive' traits into simple loci. These loci can then be pyramided via a combination of international field testing, markers assisted selection, genetically-driven crossing schemes, and genomic selection to derive climate-ready cultivars. Here, several examples of this approach are presented and their implications for 'adaptation' are discussed.
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.