Ravi P Singh, Julio Huerta-Espino
Aphids are major pests of wheat, able to cause up to 40% yield reduction solely due to direct feeding and up to 60% when feeding is combined with the transmission of viral diseases. Wheat resistance to aphids has proven to be effective in protecting yields and also in reducing the transmission rate of viral diseases. Moreover, aphid resistance is fundamental to reduce the negative impacts that the indiscriminate use of insecticides have on the environment and human health. In this study we report the results derived from the evaluation of 326 synthetic hexaploid wheat (SHW) derived lines against the greenbug (Schizaphis graminum [Rondai]). Primary SHWs were crossed with CIMMYT elite lines and further selected in the breeding pipeline. Therefore, such lines have acceptable agronomic characteristics for its further use in breeding programs. The 326 SHW derived lines were evaluated at seedling stage, in five augmented incomplete blocks, arranged in split-plots, with two treatments (infested vs. non-infested) and with resistant and susceptible checks replicated 16 times. The measured variables were chlorophyll content with a SPAD meter and a visual damage score in a scale 0-100 was also taken. Measurements were recorded when the susceptible check was dead due to aphid feeding. The evaluations were repeated two times for confirmation. Our results indicate the presence of genetic variation for S. graminum resistance. We identified about 4 % of the lines to carry high levels of resistance against this aphid. These lines are currently used in CIMMYT's bread wheat breeding program to incorporate the resistance in elite germplasm.
Institute of Plant Protection, Chinese Academy of Agricultural Sciences
Jing Feng, Ruiming Lin, Fengtao Wang, Qiang Yao, Qingyun Guo, Shichang Xu
Wheat stripe rust is an important air borne disease caused by Puccinia striiformis f. sp. tritici, and seriously threatens the safety of wheat production. Breeding and utilization of resistant varieties is the most economical, safe and effective measure to control wheat stripe rust. Sifangmai is a landrace from the state of Guangxi, China, and maintains good resistance to the current epidemic species CYR34, CYR33, CYR32 and CYR29 in China. Sifangmai was crossed with Taichung 29 to obtain F1, F2 and F2:3 to analyze its character of inheritance. In the adult stage, the cross of Sifangmai /Taichung 29 was inoculated by CYR32. The genetic analysis showed that the resistance of Sifangmai to CYR32 was controlled by a dominant gene, named as YrSF. A mapping population of F2 was genotyped with simple sequence repeat (SSR) markers. SSR loci Xgpw8015, Xgpw4098, Xwmc73, Xgpw8092, Xgpw7309 and Xbarc89 on 5B chromosome showed polymorphic between Taichung 29, Sifangmai, and resistant and susceptible pools, indicating that the resistant gene in Sifangmai was located on the 5B chromosome. The linkage map of these SSR markers was constructed and the nearest SSR to the gene is Xgpw8015. A set of Chinese Spring nulli-tetrasomic lines was used to confirm YrSF on chromosome 5B. YrSF is different from known genes in chromosome 5B. Xgpw8015 can be used as a marker for detection of YrSF.
Mohammad Kassem, Ghinwa Lababedi, Naim Al-Husien
Leaf rust is the most common rust in wheat production areas of Syria and causes significant annual yield losses. Using genotypes with durable resistance is the most economical way of controlling the disease. One of the best-known leaf rust resistance genes is Lr46 that confers a slow rusting type of adult plant resistance. The main objective of this study was to identify Lr46 in durum wheat genotypes using morphological and molecular markers. Thirty-two durum wheat genotypes were evaluated for response to leaf rust at the seedling and adult plant stages. Twelve genotypes (37.5%) were resistant (R), 10 (31.25%) were moderately resistant (MR), seven (21.87%) were moderately susceptible (MS), and three (9.37%) were susceptible (S). Molecular marker analyses using SSR marker wmc44 showed that 16 genotypes (50%) carried Lr46/Yr29. The genotypes possessing the marker linked to Lr46/Yr29 could be used for selection of Lr46/Yr29 in breeding for slow rusting resistance in durum.
Levent Ozturk, Ismail Cakmak
Zinc (Zn) deficiency is an important health problem worldwide, affecting about two billion people, especially children and women. Zinc deficiency related diseases are more prevailing in developing countries because populationa rely on cereals (i.e., wheat, rice and maize) as a staple food which are inherently low in micronutrients. Zinc concentration in cereal grains can be improved by genetic or agronomic biofortification. Optimized applications of soil and foliar Zn fertilizers has been found effective for cereals like wheat and rice but not significantly in maize. Current study focuses to elucidate the physiological reasons behind the poor response of maize to foliar applications compared to wheat. Experiments with stable isotope of Zn (70Zn) revealed the differences in leaf uptake, root and shoot translocation of foliar-applied Zn in wheat and maize. The results suggested that wheat has greater capacity for leaf absorption and translocation of foliarly applied Zn compared to maize. The increased leaf Zn uptake and localization in wheat was confirmed by a visual demonstration using Zn-responsive fluorescent dye Zinpyr and fluoresce microscopy. This study provides valuable information to maximize the uptake and deposition of foliarly applied Zn to cereal grains.
CREA-Research Centre for Cereal and Industrial Crops
Elisabetta Mazzucotelli, Oadi Matny, Antonietta Saccomanno, Raffaella Battaglia, Francesca Desiderio, Agata Gadaleta, Nicola Pecchioni, Pasquale De Vita, Giovanni Laido, Luigi Cattivelli, Brian Steffenson
The recent emergence of new widely virulent and aggressive strains of rusts (particularly stripe and stem rust) is threatening Italian durum wheat (Triticum turgidum L. var. durum) production, especially under the trend of higher temperature and humidity. A big effort has been undertaken to explore the genetic variability for resistance to these fungal pathogens and discovering novel resistance genes. In particular, a wide set of tetraploid wheat lines was genotyped with several thousands of SNP markers and used for association mapping. This large collection consisted of a group of durum wheat cultivars, produced from the beginning of the last century up to now, a collection of wild emmer wheats (T. dicoccoides), and lines belonging to other wild and domesticated tetraploid subspecies, as a large untapped source of genetic diversity. In a tight cooperation with the University of Minnesota, this collection was evaluated for reaction to several races of stem and stripe rust pathogens in both controlled greenhouse and field conditions. Among the genotypes belonging to the collection are parents of segregating populations which were used for the validation of mapping results. Novel resistance loci were identified, that can be incorporated into new durum varieties through breeding programs. The QTLs found in this study, together with those available in literature, were projected to the recently sequenced durum wheat genome in order to define more precisely the chromosome regions and candidate genes involved in resistance to rusts. Lines which were resistant to multiple races of rust pathogens were also found among both T. dicoccoides and durum wheat cultivars as a source of resistance genes, whose cloning will be undertaken based on the results here obtained.
This study was supported by the Italian Ministry of Foreign Affairs and International Cooperation, with the special grant RES-WHEAT.
Research centre SELTON
Alena Hanzalova, Jaroslav Matyk, Pavel Bartos
In the Czech Republic all three rust species on wheat occur. Leaf rust (Puccinia triticina) can be found almost everywhere, and it can cause yield losses up to 40% mainly in warmer parts of the country in South Moravia.
Yellow rust, typical for cooler climate, occurred in relatively long time intervals. However in 2013 new pathotypes tolerating higher temperatures occurred and caused yield losses. In 2016 yellow rust incidence was lower, being still important in Moravia, where yellow rust occurred already in previous years.
Stem rust incidence was very rare in the last years. However in Germany, outbreaks and new pathotypes (e.g. Digalu) of stem rust in 2013 were recorded and comeback of stem rust to Central Europe can be expected.
Rust control consists of chemical control and especially of breeding for resistance, that aims at combined resistance to all three rusts. On the scale 9 high resistance, 1 high susceptibility average 4 year rating (2013-2016) of the tested cultivars was 6.4 for yellow rust, 5.7 for leaf rust and 6.2 for stem rust.
"Triple rust resistance" was recorded in spring wheat LOTTE and winter wheat line SG-S 1684 13, high resistance to yellow rust and stem rust in the cultivar Steffi. Resistance to all three rusts of 14 winter wheat cultivars and 12 breeding lines from the Plant Breeding Station-Stupice is summarized on separate tables and described in the text.
Ethiopian Institute of Agricultural Research, Debre Zeit Research Centre
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Stem rust caused by Puccinia graminis f.sp. tritici is one of the major biotic constraints of wheat production. The disease may cause substantial quantitative and qualitative yield losses. However, much of the work in Ethiopia on this pathosystem focuses on quantitative yield loss and qualitative losses are often overlooked. Hence the current research was designed with the objectives to evaluate the effect of stem rust on physical and chemical quality of durum wheat and assess the relationships between disease intensity and quality parameters. For this purpose, a factorial field experiment was conducted at Debre Zeit Agricultural Research Centre during main and off seasons of 2016/17. The experiment involved six durum wheat varieties (Denbi, Hitosa, Tob.66, Mukiye, Ude and Mengudo) with different level of resistance to stem rust, and three Tilt spray schedules of Tilt?250 E.C at 7, 14 and 21 days. The experiment was laid out in randomized complete block design in factorial arrangements with three replications and untreated checks were included for comparison purpose. Results revealed significant variations in disease parameters and crop performance among spray schedules, wheat varieties and their interactions. Stem rust severity was the lowest on moderately susceptible and susceptible varieties treated with the Tilt at 7th day schedule. The highest stem rust severity (46.67%) was recorded on variety Hitosa without Tilt spray. Without Tilt treatment Denbi variety accounts protein content of 15.67% which is a false protein. At 7th day spray schedule this variety showed 12.90 % of grain protein content which is normal. There was a significant positive correlation between grain protein and stem rust severity (0.31**). There was significant negative relationships between terminal stem rust severity and thousand kernel weight, hectolitre weight, seed size and yield during off and main seasons were resulted, respectively.
Tel Aviv University
Assaf Distelfeld, Jacob Manisterski, Pnina Ben-Yehuda
Intensive breeding and replacement of traditional landraces by modern cultivars led to the narrowing of genetic variation in cultivated wheat. The most sustainable method for wheat improvement is utilization of genetic diversity from wheat wild relatives such as Aegilops speltoides that has a diversity of genes for resistance to leaf rust (LR). A high pairing-inducing Ae. speltoides strain collected from Israel was introgressed into T. turgidum subsp. durum var. landrace Nursi. The F1 plants were treated with colchicine to induce chromosome doubling. The resulting hexaploid plants were crossed to bread wheat cv. Beit-Lehem and F3 plants were backcrossed three times to bread wheat cv. Barnir. Each generation was selected for LR resistance to P. triticina isolate #1010 and five resistant wheat-Ae. speltoides introgression lines (ILs) designated DK1 to DK5 were selected. These Ae. speltoides ILs were genotyped using the 90K Infinium SNP assay and most of the polymorphic markers were mapped to chromosome 1B suggesting that the Ae. speltoides introgressions encompass most of this chromosome. To test if the newly identified gene is identical to Lr51, that was also introgressed from Ae. speltoides to chromosome 1B of bread wheat, the DK ILs were genotyped with the molecular marker AGA7 that was shown to be linked to Lr51. The Ae. speltoides AGA7 allele was absent in the DK ILs suggesting that these genotypes are not carrying the Lr51 introgression. Moreover, we performed an allelism test. Spring wheat cv. Kern harboring resistance gene Lr51 was crossed with DK2 and an F2 segregation ratio of 15R:1S was obtained, indicating that the resistance was conditioned by two independent dominant genes. Overall, our results suggest that DK2 carries a new leaf rust resistance gene from Ae. speltoides and this gene has potential for wheat improvement.
Fatima Gaboun, Nasserlhaq Nsarellah, Keltoum Rhrib, Atmane Rochdi
Durum wheat landraces have constituted the main source of Moroccan wheat production until the first half of the last century. This local germplasm is still cultivated in less favorable environments particularly in mountains and sub-Saharan regions. In recent decades of the late 20th and early 21th centuries, the genetic improvement had led to the release of new durum wheat cultivars highly uniform and more productive. The present paper investigates the evolution of genetic variability in terms of productivity and quality related traits using an historical series of Moroccan durum wheat genotypes grouped according to their period of release into "Landraces/ Old cultivars," "Intermediate cultivars," and "Modern cultivars". A significant improvement was achieved in durum wheat Morroccan productivity. Modern cultivars exceed their predecessors in terms of productivity related traits. The genetic gain was clearly associated with a reduction in plant cycle and plant height lowering the straw yield which resulted in an increase of grain yield estimated to 15.42Kg/ha/year. However, results revealed a reduction in terms of almost all quality related traits; -0.12% per year for protein content, -0.30 % per year for gluten strength, -0.31% per year for yellow pigment content, and -0.19% per year for vitreousness. The results underline the important variability in grain quality attributes among landraces genotypes. This local germplasm may be used as sources of quality-improving attributes in durum wheat breeding program to develop new varieties combining both high productivity and grain quality.
Wheat Diseases Department Plant Pathology research Institute, Agriculture Research Center.
Improvement of wheat (Triticum aestivum L.) is a major goal of plant breeders and pathologists to ensure food security and self sufficiency. Relationship between different levels of stem, stripe and leaf rust severity on the two grain yield components (1000-kernel weight and plot yield) were studied during 2015/2016 and 2016/2017 seasons at Sids Agricultural Research Station. Different epiphytotic levels of stem, stripe and leaf rust were created using spreader artificial inoculation and spraying the fungicide Sumi-eight. To create different rust severity, one, two, and three sprays were applied at 7 day intervals. Protected control treatment was obtained by spraying the fungicide four times. Correlation coefficient (R<sup>2</sup>) analysis depicted that positive correlation was found between different rust severity levels and yield loss. In 2015/2016 growing season, which stem rust started early, disease severity (%) reached its relatively high percentage (80%) with the highest loss (%) in both 1000 kernel weight (36.3%) and plot weight (37.82%). The effect of stripe rust infection on yield components was lower than those of stem rust and lowest in leaf rust. On the other hand, the lowest loss was observed with 10% of stem, stripe and leaf rust which sprayed three times. During 2016/2017 stripe rust infection caused the highest loss (%) in yield components, under the highest level 80% of severity, on the other hand leaf rust showed low level of loss (%) Compared with the stripe and stem rust.