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.
Ayub Agricultural Research Institute, Faisalabad
Different biotic and abiotic stresses are hampering wheat yield across different geographic regions. Among biotic stresses, wheat rusts are principal cause of yield reduction. Whereas among abiotic stresses, drought is the principle cause of reduction in growth and lowering yield potential. So developing rust resistance and drought tolerance in wheat germplasm is needed, which requires assessment of genetic potential of current cultivars against these stresses to identify variation among existing germplasm. Screening of genotypes under naturally prevailing races of rust species is the better and inexpensive approach. In the present study 65 genotypes including five checks (AARI-11, Chakwal- 50, Aas- 11, Morocco and Galaxy-13) were evaluated for adult plant response to wheat rusts and water deficit conditions. Experimental material was planted in four blocks each having new entries along with repetition of five checks in augmented design. Data was recorded on morphological traits including plant height, peduncle length, spike length, productive tillers per meter, flag leaf area, number of spikelet per spike, grains per spike, single head weight, 1000 grain weight, days to maturity and grain yield per acre. Significant variation was observed among genotypes for all the studied traits. On the basis of performance G39 and G36 were better than commercial drought check Chakwal-50 in almost all the traits. However rust screening under natural rust infestation revealed that although Morocco showed susceptible (S) response yet only six genotypes were susceptible to yellow rust whereas all others were resistant. In case of leaf rust 29 were completely resistance, 25 were moderately resistant, seven were moderately susceptible and only four were completely susceptible to currently active races of leaf rust. However, in the case of stem rust, 61 genotypes showed complete resistance to stem rust, two showed moderately resistance and two were moderately susceptible. Information obtained from this study would be favorable for breeding rust resistant and drought tolerant cultivars.
University of Eldoret
Julius Ochuodho, Ruth Wanyera, Sridhar Bhavani, Les Szabo
Stem rust Ug99 and related race group are one of the major constraints of wheat production in Kenya. The challenge has been largely due to rapid evolution of races within lineage defeating resistance genes resulting in boom and burst cycles. Understanding of the pathogen population structure in major wheat growing regions in Kenya gives comprehensive information of the predominant races as well as capturing new races which may have potential of causing epidemics. Such information can have significant impact on effective gene stewardship in breeding resistant varieties. Using 11 Pgt Simple Sequence Repeats (SSR) markers we analyzed 104 single uredinial-pustule samples. Allele frequency distribution ranged from 2 to 6 per locus with an average of 3.27 per locus. Observed heterozygosity ranging from 0.297-1.000 (mean HO=?0.809) was significantly different (P< 0.001) than the expected heterozygosity (0.264 to 0.507; mean HE=?0.407) indicating that the population is asexual. Analysis of molecular variance (AMOVA) showed that the majority of the variation occurred within the samples (98%) rather than between regions (2%). Analysis of 104 samples identified 21 multiple locus genotypes (MLGs). MLG.19 was observed across the three region analyzed that is Central Rift, North Rift and Mount Kenya while MLG.18 was predominant in Mount Kenya. Based on SSR genotypes of reference isolates, Pgt clade IV (race TKTTF) was associated with MLG.16 in Central Rift Kenya while clade I (race TTKSK) had a unique MLG.10. These results indicated two main groups corresponding to Clade I (Ug99 race group) and Clade IV (race TKTTF race group). This minimum spanning network analysis pattern points to the Pgt population being asexual due to mutation. These preliminary results suggest that Pgt population in Kenya is asexual in nature. Further analysis is being conducted to ascertain geographical structure as well as compare the results with the 2011 data.
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
1,3 Colegio de Postgraduados-Fitosanidad, Campus Montecillo, Texcoco, 56230, Estado de M?xico, M?xico
Julio Huerta-Espino, Ravi P. Singh, Caixia Lan, Sridhar Bhavani, Reyna I. Rojas-Martínez, Ignacio Benitez-Riquelme, Cristian Nava-Díaz, Mandeep Singh Randhawa
Leaf rust and stripe rust caused by the fungi Puccinia triticina and P. striiformis f. sp. tritici, respectively, are important diseases of wheat and represent a significant threat in most wheat producing regions worldwide. Growing resistant varieties and the identification and characterization of new sources of resistance are necessary to combat the threat from the evolving pathogen population. Bread wheat (Triticum aestivum L.) line 'Kijil' developed at CIMMYT showed adult plant resistance (APR) to leaf rust (LR) and stripe rust (YR). The genetic basis of the resistance was investigated using 198 recombinant inbred lines (RILs) derived from the cross of susceptible Apav#1 and resistant Kijil. Field phenotyping of parents and RILs were conducted at El Batón, Toluca and Ciudad Obregon, Mexico during 2016 and 2017. Pearson correlation coeffcients (P< 0.0001) were high for disease severities between two years of evaluations: LR (r= 0.90) and YR (r= 0.83). Correlations (r= 0.30-0.76) were also significant between LR and YR in all environments. Genetic analyses indicated that 3 to 5 genes of additive effects governed resistance to both rusts. RILs carrying the pleiotropic APR gene Lr46/Yr29/Sr58 showed 23 and 41% of disease severity for LR and YR respectively, whereas lines lacking it had 55 and 78% severities. RILs positive for Sr2/Yr30 showed 66% YR severity, whereas those negative displayed 78%. In addition, lines carrying the race-specific gene Yr17/Sr38 showed 28% YR severity in contrast to non-carriers that displayed 78% severity. We conclude that Kijil possesses a complex nature of resistance.
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.
CSIRO Agriculture and Food, Australia
Timothy Hewitt, Peng Zhang, Zacharias A. Pretorius, Narayana Upadhyaya, Rohit Mago, Sambasivam Periyannan, Xiuying Kong, Burkhard Steuernagel, Brande H. Wulff, Evans S. Lagudah
Multiple rust resistance gene combinations are considered as a practical solution for providing durable rust resistance and preventing resistance breakdown arising from single gene deployment. The stem rust resistance locus Sr26, originally derived from Thinopyrum ponticum and introgressed into wheat as a chromosome translocation, is one of the very few genes conferring durable resistance for almost 40 years to all known races of stem rust, including the highly virulent stem rust race Ug99 (TTKSK) and its derivatives (Dundas et al. 2015). To understand the underlying mechanisms of its unusual long-term effectiveness and to explore allelic diversity in different Th. ponticum accessions for other functional alleles that may offer new sources of resistance, we used comparative genomics and gene capture techniques (Resistance gene enrichment sequencing, RenSeq) as complementary strategies for isolating the target gene (Steuernage et al. 2016). Sr26 region was first mapped using NB-LRR (Nucleotide-binding site and leucine-rich repeat) sequences from the orthologous gene members located on the long arm of chromosome 6D from Aegilops tauschii (the D-genome donor of wheat) reference genome. Subsequently, we revealed a cluster of NB-LRR sequences located at the distal end of the Th. ponticum introgression segment that were absent in the smallest interstitial Sr26 deletion mutant. Therefore, we substantially narrowed down the genetic interval for Sr26. In addition to this approach, we subjected the mutant population to RenSeq pipeline. A candidate gene of Sr26 has been successfully identified to be a NBS-LRR type resistance gene. Validation of the gene candidate by complementation studies is currently in progress. In order to enhance durable resistance, genetic stocks of Sr26 from different backgrounds as well as a panel of Sr26-APR (Adult Plant Resistance) gene combinations have been generated to further investigate the resistance response of Sr26 in combination with different multi-pathogen APR genes.
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.
Omsk State Agricultural University, Omsk, Russia
Elena Salina, Yuriy Zelenskiy, Alma Kokhmetova, Mehran Patpour, Mogens Hovmøller, Pablo Olivera, Les Szabo, Yue Jin, Marcel Meyer, Chris Gilligan, Matthew Hort, Dave Hodson, Alexey Morgunov
Short season, high latitude spring wheat is grown on 7 million ha in Western Siberia and 10 million ha in Northern Kazakhstan. Despite relatively low wheat yields (1.5 t/ha), the region is extremely important for regional and global food security. Leaf rust dominates, occurring three years out of five, especially in favorable years with higher rainfall. Since 2010, stem rust has been observed at an increasing number of sites. The first large-scale stem rust outbreak occurred in 2015 and affected about 0.5-1 million ha in Omsk, Western Siberia. In 2016, 2 million ha were affected in the Omsk and Altay regions, while 1 million ha in the Kostanay and Northern Kazakhstan regions were affected in 2017. Estimated yield losses reached 25-35% each year. Factors associated with the outbreaks included: higher rainfall in late June and July; cultivation of susceptible varieties; and an increased area planted to winter wheat, which serves as a source of inoculum. Sampling and race analysis revealed a diverse pathogen population, indicative of a sexual recombination. A total of 51 races were identified from 31 samples taken in 2015 and 2016. All races were avirulent on Sr31. The majority of varieties released and cultivated in the region are susceptible to stem rust and require replacing. A recent study of 150 local resistant varieties and breeding lines indicated that the genetic basis of resistance was limited to Sr25, Sr31, Sr36, Sr6Ai, Sr6Ai#2, and additional unknown major genes. Adult-plant resistance to stem rust was observed in less than 20% of the germplasm. The potential impact of these large stem rust outbreaks on other wheat growing regions is being investigated by analyzing spore wind dispersal patterns. Further research is required to understand and mitigate the sudden appearance of stem rust as a disease of economic importance.
Study at Omsk State Agrarian University was supported by the Russian Science Foundation (project No. 16-16-10005).
University of Minnesota
Ayele Badebo, Worku Bulbula, Matthew Rouse, Yue Jin
Our research objective is to identify new resistance genes in durum wheat that are effective against TTKSK and other significant stem rust pathogen races that could be utilized in durum breeding. We characterized 8,000 accessions for stem rust response in the field (Debre Zeit, Ethiopia, and St. Paul, MN). Accessions with resistant to moderately resistant responses in multiple field evaluations were evaluated at the seedling stage for resistance to races TTKSK, TRTTF, TTTTF, JRCQC, TKTTF, and six representative U.S. races. We identified 438 durum accessions resistant to moderately resistant in all field evaluations. Among the field-resistant accessions, 273 were resistant to all races used in seedling evaluations. Accessions susceptible at the seedling stage are being evaluated for the presence of adult plant resistance genes. The highest frequencies of resistant lines include landraces from East and North Africa (Ethiopia and Egypt) and advanced breeding lines and cultivars from North America (Mexico and USA). DNA markers will be performed to identify the presence of durum stem rust resistance genes, including Sr13, Sr8155B1, Sr11, and Sr8a. Nineteen resistant accessions were selected to investigate the genetics of TTKSK and TRTTF resistance. Results from evaluating F2 and F2:3 generations from biparental crosses revealed that resistance to race TTKSK was conferred mostly by one or two genes with dominant and recessive actions. Additional resistance genes were identified when populations were evaluated against race TRTTF. A bulk segregant analysis approach is being used to map the resistance in selected lines using the 90K SNP platform.