Yellow rust is the most dangerous of the wheat rusts worldwide. Disease management involves breeding and fungicide application, with the former being more cost effective and environmentally acceptable. Despite the release of numerous yellow rust resistant cultivars in many countries, new aggressive strains inevitably overcome the resistances in a zigzag or ‘boom and bust’manner. For example, Chamran (Attila-50-Y), released in 1997 in Iran, immediately became the most popular cultivar nationally. In 2012-2013, a new aggressive Pst strain overcame the resistance in Chamran as well as Vee/Nac (an early maturity line suitable for the wheat-maize cropping system) in Khuzestan, a major wheat-producing region in the southwest of the country. Evaluations of wheat germplasm at the Safiabad Agricultural Research Center (North Khuzestan) identified 17 completely or partially resistant lines. Pedigree analyses of resistant lines identified Batavia, Genaro 81, Opata, Pastor, Trap and Yaco as possible sources of resistance. Genotype information of these cultivars obtained from the http://wheatpedigree.net/ database indicated the presence of Yr33, Yr30+Yr18 and Yr31 in Batavia, Opata and Pastor, respectively. Genaro 81, Trap and Yaco carry Yr18. Currently, F2 populations of 34 crosses of 17 resistant lines to locally adapted cultivars Chamran and Vee/Nac are undergoing field selection in a nursery inoculated with the 2012-2013 aggressive race. The progenies of selected plants will undergo further testing and selected homozygous F3 lines will be genotyped for markers associated with Yr18 (Xgwm295-7D), Yr30 (flanking markers Xgwm533.1 - Xgwm493-3B), Yr31 (Xgwm630/Xgwm374-2B (Lr13/Lr23)) and Yr33 (flanking markers Xgwm111 - Xgwm437-7D).
Primary Author: Ghaffary, Safiabad Agricultural Research Center, Iran
Wheat is the most important cereal crop in Pakistan because it contributes major portions of daily calorie intake. Rust is an increasing threat to wheat production and ultimately food security in Asian countries. The purpose of the present study is to identify the suitable wheat lines that could significantly resist rust pathogen without compromising yield. 60 durum wheat lines, entered in preliminary and regular yield trials, were tested for various morphological and physiological traits along with adult plant disease reaction under natural rust infestation. Results indicated that there was higher incidence of yellow rust as compared to leaf rust as ten genotypes were susceptible to leaf rust. Whereas seven lines were moderately susceptible, 14 were moderately resistant and two were completely susceptible to yellow rust. These findings suggested that future breeding program should be directed towards the developments of resistant cultivars that could resist variable strains of rust pathogen under changing climatic conditions.
Primary Author: Ghafoor, Wheat Research Institute, Ayub Agricultural Rsearch Institute Faisalabad
Meeting food security challenges is a high priority in many developing countries. North African countries are among those with the highest per capita wheat consumption in the world and chronic grain deficits. Climate change scenarios predict decrease of rainfall and increase of temperature with negative impact on crop production and hence food security. Along with adoption of modern technologies, breeding higher yielding and more climate change resilient wheat varieties is widely seen as a tool that can sustain past yield gains and food production increases. Durum wheat production in Tunisia greatly benefited from the green revolution ingredients. Continued breeding lead to replacement of the early semi dwarf varieties with higher yielding, better disease resistant and more drought tolerant ones that have positively impacted yield at farmer and national level. Monitoring gains from increased yield potential and resistance to the most damaging foliar diseases, mainly septoria leaf blotch, leaf rust and stripe rust, showed that grain yield of recently released varieties is up to four times that of the tall late maturing landraces grown before the 1970's and up to 2.5 times that of varieties of the early years of the green revolution. Chlorophyll content, green leaf duration, deeper root development from diverse donors including wild wheat relatives and grain yield are being integrated in the breeding program for the selection of more drought and heat stress tolerant durum cultivars
Primary Author: Gharbi, National Institute of Agriculture Research, Tunisia
Adult Plant Resistance (APR) genes are broad-spectrum, partial-resistance genes that have the potential to contribute to sustainable control of wheat rust diseases. However, their isolation and characterization are complicated by the lack of precise molecular markers required for their identification, and therefore their use in plant breeding programs has been limited. Recent developments including the falling cost of sequencing and the increasing use of sequence capture methods to reduce genome complexity have enabled previously intractable methods such as mutational genomics to clone genes in wheat. Despite their increasing ease of use, many of these approaches require prior knowledge of the gene space and, in some cases, the gene family of the target gene to be cloned. As the APRs cloned so far do not belong to any common gene family, it is not possible to use general features of these identified APRs to conduct biased searches for novel APRs. This project aims to use an unbiased gene isolation technique called MutChromSeq, which combines chromosome flow-sorting and mutational genomics, and is independent of fine mapping, to rapidly clone the recently discovered APR gene Lr68 (Leaf Rust 68). Cloning APRs allows breeders to trace genes cheaply and quickly using gene-specific markers, enabling them to build effective and durable resistance gene pyramids. It also allows us to elucidate any common mechanism of action they have, helping researchers and breeders understand better the basis of their durable resistance. At the same time, the generation time of wheat has become one of the major limiting factors for the response time of breeders to rust epidemics. Thus, this project also aims to combine marker-assisted selection with accelerated generation advancement ('speed breeding') for rapid germplasm structuring and field performance evaluation.
Primary Author: Ghosh, John Innes Centre
Studies have shown that women farmers are worse off than the male counterparts in terms of adoption of improved varietal technology and hence they experience low productivity. This technology adoption gender gap affects agricultural development considering that women in Kenya play a significant role in agriculture and food production. The link between gender and adoption is likely to vary across cultures and over time. The hypothesis of significant gender differences in access to and use of productive resources and adoption of improved wheat varieties was tested. Based on bivariate analysis, significant differences in access and use of productive resources between men and women farmers were observed. Men were more likely to access credit, extension services, own and cultivate more lands compared to women. Similarly, women in female-headed households were less likely to access the productive resources compared to women in male-headed households. The factors that affect adoption of improved wheat varieties among smallholder farmers were analysed with a specific focus on women. In contrast to the conventional model of using gender of the household head, gender and plot levels analyses were conducted. The results show that the gender of the field owner had a negative effect on adoption of improved wheat varieties. This indicates that, men were more likely to adopt improved wheat varieties, compared to women farmers. Moreover, the level of education of the household head, household size, and access to credit and extension services were observed to significantly increase the likelihood of farmers adopting improved wheat varieties. In the same framework, female farmers in male-headed households who had access to credit were more likely to adopt improved wheat varieties while there was greater probability of adoption of improved wheat varieties among female farmers in female-headed households who had access to agriculture extension and belonged to a farmer organization
Primary Author: GICHANGI, KENYA AGRICULTURAL AND LIVESTOCK RESEARCH ORGANIZATION (KALRO)
The model grass Brachypodium distachyon has been used to study nonhost resistance mechanisms to the wheat stripe rust pathogen, Puccinia striiformis f. sp tritici. Numerous B. distachyon accessions were screened with an array of UK and Australian P. striiformis isolates and distinct infection phenotypes identified, ranging from complete resistance to partial susceptibility. Three mapping families were established - BdTR10H x TEK4, BdTR13K x Bd21 and ABR6 x Bd21 - and immunity was dominantly inherited when they were tested with one Australian and three UK isolates. Depending upon the mapping family, between one and three genes for stripe rust resistance were present and designated Yrr1 to Yrr3. Yrr1, which is present in all three families, was effective against all isolates and was fine mapped to a 100 kilobase region containing six candidate genes. Interestingly, no candidate was homologous to a known resistance gene. Yrr2, which is present in the BdTR13K x Bd21 and ABR6 x Bd21 families, is race-specific and was mapped to a 1 megabase region that contains multiple, classic NBS-LRR resistance gene candidates. Yrr3, which is present in the ABR6 x Bd21 family and effective against all isolates, was mapped to a 400 kilobase region also containing NBS-LRR gene candidates. Agrobacterium-mediated transformation of Yrr1 candidates is underway in Brachypodium for complementation, and in common wheat to test for interspecies transfer of characterized resistance.
Primary Author: Gilbert, CSIRO Plant Industry, Australia
Malnutrition affects more than 2 billion people across the globe, particularly zinc and iron deficiency causes major health problem in developing world. The biofortified staple food crops such as wheat, is an important channel to contribute to the hidden hunger problem in low income countries. Breeding for enhanced zinc concentration in wheat was initiated by crossing high zinc sources identified among synthetic wheats, T. dicoccum, T. spelta and landraces. These crosses have resulted in wheat varieties with competitive yields and enhanced grain zinc were adapted by farmers in South Asia. CIMMYT-derived early-maturity wheat cultivar 'Zinc-Shakti' with about 40% increased zinc (+14 ppm), is now grown in eastern India through public-private partners. The two CIMMYT-derived biofortified varieties: 'WB2' and 'HPBW01' released in 2016 for northwestern plains zone of India. In Pakistan, 'Zincol' was released in 2016. The first high zinc wheat variety (Bari-Gom 33) with better resistance to wheat blast have been released in Bangladesh for commercial cultivation in 2017. Targeted crosses with increased population sizes were used to obtain superior progeny lines that have high zinc levels in combination with other essential traits. This has resulted in the incorporation of several novel alleles for grain zinc and iron in elite, high-yielding germplasm. High zinc and iron are under quantitative genetic control and further progress is possible as multiple QTL are pyramided in high yielding wheats. High-throughput, non-destructive phenotyping for grain zinc and iron using the X-ray fluorescence (XRF) analysis has facilitated the selection dramatically. Gene discovery and mapping studies leading to the utilization of markers to further improve the breeding efficiency. Rapid adoption of high zinc wheat varieties in South Asia and beyond is expected with the second wave of high zinc wheat lines with superior yield, heat and drought tolerance and resistance to rusts and other foliar diseases.
Primary Author: Govindan, CIMMYT
RNA interference (RNAi) is a powerful genetic tool to accelerate research in plant biotechnology and to control biotic stresses by manipulating target gene expression. However, the potential of RNAi in wheat to efficiently and durably control the devastating stripe rust fungus Puccinia striiformis f. sp. tritici (Pst), remained largely under explored, so far. To address this issue, we generated transgenic wheat lines expressing double-stranded RNA targeting PsFUZ7 transcripts of Pst. We analyzed expression of PsFUZ7 and related genes, and resistance traits of these transgenic wheat lines. We show that PsFUZ7 is an important pathogenicity factor that regulates infection and development of Pst. A PsFUZ7 RNAi construct stably expressed in two independent transgenic lines of wheat confers strong resistance to Pst. Pst hyphal development is strongly restricted, and necrosis of cells in plant resistance responses was induced significantly. We conclude that trafficking of RNA molecules from wheat plants to Pst may lead to a complex molecular dialogue between wheat and the rust pathogen. Moreover, we confirm the RNAi-based crop protection approaches can be used as a novel control strategy against rust pathogens in wheat.
Primary Author: Guo, Northwest A&F University
Intracellular calcium changes during plant–pathogen interaction are essential early events leading to both local and systemic acquired resistances. Salicylic acid, a critical messenger, is also required for both responses. However, the relationship between the CBL-CIPK and SA signaling pathways during wheat–Pst interaction is unclear. In this study, we isolated seven wheat CBL and 11 wheat CIPK genes and designated them as TaCBL1, 2, 3, 4, 6, 7, 9 and TaCIPK2, 5, 7, 9, 10, 14, 15, 17, 23, 31, 32. Some wheat CBLs and CIPKs were functionally characterized. Concurrently, wheat TaNPR1 as a master regulator of SA-mediated host response during Pst infection was functionally characterized. Silencing of TaCBL4, TaCIPK10 and TaNPR1 permitted increased rust development in a wheat variety that was resistant to Pst pathotype CYR23. Decreased levels of salicylic acid (SA) were observed in TaCBL4- and TaCIPK10-silenced wheat plants. Yeast two-hybrid and biomolecular fluorescence complementation (BiFC) revealed that TaCIPK10 interacted with both TaCBL4 and TaNPR1. These results suggest that a TaCBL4-TaCIPK10-TaNPR1 complex is involved in innate immunity of wheat to Pst.
Primary Author: Guo, State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, PR China
Global food security is faced with many threats including population growth and changing climate. To cope with these threats a new paradigm shift is required to ensure sufficient and sustainable crop production. Hybrid technology could represent a partly strategic solution for durum wheat, but the understanding of its heterotic behavior is very limited. In this study, 53 F1 plants were produced via half diallel scheme and North Carolina design II, using as parental elite lines selected on the basis of their genetic distance. These hybrids along with their parents were evaluated for different physiological and root traits on a precision phenotyping platform (Lemnatec) at different levels of water stress. Additionally, a second root test was conducted in near field condition via a basket method to determine shallow or deep rooting behavior. Hybrids with the most heterotic combinations in terms of above and below ground biomass were identified. However, in order to ensure adequate pollination between heterotic parents, their flowering time must overlap. To identify good matching partners, a GWAS study was conducted to identify genomic regions associated with the control of flowering time in durum wheat. A total of 384 landraces and modern germplasm were assessed at 13 environments with different temperatures and day length throughout the season. Genotyping was conducted by 35K Axiom array to generate 8,173 polymorphic SNPs. In total, 12 significant QTLS for landraces and 17 QTLs for modern germplasm were identified consistently across environments. These two results when combined will allow to predict the best parental partners for hybrid production via markers screening on the basis of their genetic similarity to the most heterotic groups, and with matching flowering times.
Primary Author: Gupta, University of Bologna, Italy/ International Center for Agricultural Research in the Dry Areas, Morocco