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.
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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.
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
Durum wheat is second important crop after bread wheat and it was grown as spring and winter type in Turkey. Rusts are the most important diseases limiting durum wheat production in Turkey. The aim of the study was determining of the resistance of the 232 Turkish winter durum wheat genotypes in preliminary yield trials developed by the Central Research Institute for Field Crops (CRIFC) to rusts. For this purpose, adult plant and seedling test were conducted for yellow rust while only seedling test were conducted for leaf and stem rust. Evaluations were carried out at the research facilities of CRIFC at İkizce and Yenimahalle in Ankara in the 2014 season. For adult plant reactions; the genotypes were inoculated with local Pst populations (virulent on Yr2,6,7,8,9,25,27,Sd,Su,Avs). Stripe rust development on each entry were scored using the modified Cobb scale when the susceptible check cv. Little Club had reached 80S infection severity in June, 2014. Coefficients of infections were calculated and values below 20 were considered to be resistant. For seedling test; the seedling was inoculated with local Pgt (avirulent on Sr24, Sr26, Sr27, and Sr31), Pt (avirulent on Lr9, Lr19, Lr24, and Lr28) and Pst populations. Stripe, leaf and stem rust development on each entry were scored after 14 days with 0-4 and 0-9 scale for leaf-stem rust and yellow rust, respectively. In seedling stage, 141(65%), 41(18%), and 114 (49%) genotypes were resistant to local Pgt, Pt, and Pst populations, respectively. In adult plant test, 21 (9%) genotypes were resistant to Pst. The resistance genotypes to stem, leaf, and stripe rust were determined with this research.
The Lr34 resistance gene from Triticum aestivum encodes a putative ABC transporter protein that confers broad spectrum, partial adult plant resistance to all three rusts species and powdery mildew. It has remained a durable source of resistance for over 100 years in which time no increased virulence towards Lr34 has been observed. This gene is located on chromosome 7D and consequently cannot be readily transferred to durum wheat by traditional breeding. A transgenic approach was used to transfer Lr34 to durum wheat cultivar Stewart by Agrobacterium transformation. Homozygous progeny from a number of independent Stewart lines expressing Lr34 under regulatory control of its endogenous promoter showed high levels of rust resistance at the seedling stage. A correlation between seedling resistance and transgene expression levels was observed in these plants. In contrast seedlings from a near isogenic line of hexaploid wheat cultivar Thatcher containing Lr34 showed only a minor difference in rust growth when compared with Thatcher seedlings, typical of this adult plant resistance gene in hexaploid wheat. Little is known about how the Lr34 gene product functions; however, the seedling resistance of these durum transgenics enables functional assays to be readily undertaken without the need for adult plant material. By infecting seedlings we have shown that day length has an effect on Lr34 resistance to leaf rust, with higher levels of resistance observed under long days (16 h light) compared with short days (8 h light). This study demonstrates that Lr34 provides strong and presumably durable seedling resistance to rust in durum plants that can be used to further understand how this gene confers resistance.
The CIMMYT durum Bairds is susceptible to leaf rust (LR) at the seedling stage but shows an adequate level of slow rusting adult plant resistance (APR) in Mexican field environments. A recombinant inbred line (RIL) population developed from a cross of Bairds and the susceptible parent Atred#2 was phenotyped for LR response at Ciudad Obregon, Mexico, during 2013, 2014 and 2015 under artificial epidemics created with Pt race BBG/BP. Genetic analysis indicated that 3-4 additive genes conferred LR resistance. The RILs and parents were also genotyped with the 50K diversity arrays technology (DArT) sequence system and 93 SSR markers. A genetic map comprising 1,150 markers was used to map the resistance loci. Inclusive composite interval mapping analysis detected four quantitative trait loci (QTL) on chromosomes 1BL, 2BC (centromere region), 5BL and 6BL. These QTL, designated as QLr.cim-1BL, QLr.cim-2BC, QLr.cim-5BL and QLr.cim-6BL, explained 20.1-60.7%, 6.4-13.1%, 4.3-11.2%, and 7.1-28.0%, respectively, of the variation in leaf rust severity. QLr.cim-1BL was close to the previously reported APR gene Lr46, whereas QLr.cim-6BL, detected in all three seasons, is a new resistance locus in durum wheat. The four QTL combined showed a significant additive effect on resistance with a disease severity of 18-20%, whereas RILs carrying the individual QTL showed mean leaf rust severities ranging from 56 to 98%. Three QTL, except for QLr.cim-2BC, were derived from Bairds. The final LR severity of Bairds ranged from 15-25% across three years. This cultivar can be used as a source for complex APR in durum wheat breeding.