CIMMYT International Research Articles

First report of expansion of virulence in Puccinia striiformis f. sp. tritici to wheat resistance genes Yr10 and Yr24 in the Middle East.

Over the last decade, field assessments of the yellow rust differential lines for resistance genes Yr10 and Yr24 and race analysis in the Middle East have demonstrated efficient yellow rust control by Yr10 and Yr24 (=Yr26). Yellow rust samples collected during 2018-21 in Central West Asia & North and sub-Saharan Africa underwent race analysis at the Regional Cereal Rust Research Center in Izmir, Türkiye. The infected leaf segments were subjected to rehydration at 20°C for three hours. Subsequently, the leaf segments were rubbed on the first leaves of seedlings of susceptible cultivar Morocco. Inoculated seedlings were placed at 10°C in dark conditions with 95% humidity for 24 hrs, then moved to a growth chamber with a 16-hr light (220 µmolm-2s-1) cycle at 15°C and an eight-hour dark period at 12°C. Urediniospores were collected 15 days post-inoculation. A set of yellow rust differential lines including Morocco, Avocet 'S', Avocet 'R', Yr1/6* Avocet 'S', Kalyansona (Yr2), Vilmorin 23 (Yr3), Hybrid 46 (Yr4), Yr6/6* Avocet 'S', Yr7/6* Avocet 'S', Yr8/6* Avocet 'S', Yr9/6* Avocet 'S', Yr10/6* Avocet 'S', Moro (Yr10+), Yr17/6*Avocet 'S', Yr24/6* Avocet 'S', TP1295 (Yr25), Yr27/6* Avocet 'S', YrSp/6* Avocet 'S', Spalding Prolific (YrSP), Strubes Dickkopf (YrSD), Tres/6*Avocet'S', Cham 1, and Ambition was used in race analysis. A mixture of 2 mL Soltrol® and 0.5 mg fresh urediniospores was used to inoculate 10-day-old seedlings of the 23 differential varieties. Pre-inoculation, incubation, and post-inoculation conditions were the same as above. Seedling infection types (ITs) were recorded 15 days post-inoculation on a scale of 0 to 9 (McNeal et al. 1971), where ITs 0 to 6 are classified as low infection types (LITs= avirulent) and ITs 7 to 9 categorized as high infection types (HITs= virulent). HITs of 7 to 9 were observed for the first time on Yr10/6* Avocet 'S', Yr24/6* Avocet 'S', as well as on Moro (Yr10+) for 25 sample of the total 50 isolates from Lebanon and Türkiye in 2018. During the race analysis in 2019 to 2021, virulence for Yr10 and Yr24 was identified among tested samples from Egypt, Lebanon, Jordan, Syria, and Türkiye, indicating the expansion of virulence for Yr10 and Yr24 into new regions. HITs were observed for the durum wheat cultivar Cham 1 and wheat cultivar Ambition in all races. Virulence for YrA, Yr2, Yr6, Yr7, Yr8, Yr17, and 32 was common within the Yr10 and Yr24 virulent races, and virulence for YrSp and Yr27 were observed in low frequency. Molecular genotyping of 209 isolates, including the Yr10 virulent races, was performed using 19 microsatellite markers (Ali et al. 2017; Rodriguez-Algaba et al. 2017) and aligned with the Puccinia striiformis nomenclature system of the Global Rust Reference Center (GRRC). The results showed that 66 isolates were identical to the genotyping lineage "ME2018" identified in Egypt in 2018 by GRRC. This genetic lineage has now been designated as PstS17 (Hovmøller et al. 2023). The durum wheat cultivars have always been resistant to yellow rust in the Middle East. Seedling tests of 50 durum advanced lines from CIMMYT's International Durum Wheat Yield Nursery showed LITs in 45 accessions (90%) against an avirulent race for Yr10 and Yr24 (PstS2), but only 12% remained resistant while tested with a PstS17 (virulent for Yr10 and Yr24). This observation provides compelling evidence of the Yr10 and/or Yr24 presence within tested durum wheat germplasm. Continued monitoring of virulence and resistance of wheat germplasm to yellow rust is critical for successful breeding for rust resistance.

Using the gene pool of CIMMYT cultivars and lines in spring durum wheat breeding in Western Siberia

Background. Preservation and expansion of the source material genetic diversity and its purposeful use is the basis for the development of adaptable spring durum wheat cultivars for the environments of Western Siberia.Materials and methods. The target research material included the cultivars and promising material of Triticum durum Desf. developed in the Spring Durum Wheat Breeding Laboratory of Omsk Agrarian Scientific Center as well as the gene pool of cultivars and lines obtained under the CIMMYT International Cooperation Program. Field trials, disease resistance assessment and phenological observations were carried out on the experimental fields of the Institute in 2000–2020 according to generally accepted methods. Principal component analysis was carried out using the R version of the 4.0.3 package.Results. The studies have shown that CIMMYT lines differ from local cultivars and lines in disease resistance (brown rust, stem rust, hard smut, and powdery mildew), test weight, pasta-making properties, and lodging resistance, but under the conditions of Western Siberia they are significantly inferior in adaptability to local cultivars and lines and suffer greatly from drought, especially during the grain-filling period. In the genetic control of the studied traits, the additive-dominant system with the inclusion of the complementary recessive epistasis prevails. Local cultivars dominated in most of the studied traits, except the stem length, and the length and diameter of the second internode, where short-stemmed cultivars affected the degree of the traits’ expression in hybrids.Conclusion. The result of such activity was the release of cv. ‘Omsky Korall’, which combines high yield, adaptability to the climate of Western Siberia, and resistance to the local population of Puccinia graminis Pers. f. sp. tritici Erikss. et Henn. and Ug99, with excellent pasta-making properties, as well as the presence of promising lines in all breeding nurseries.

Selection signatures in the CIMMYT International Elite Spring and Semi-arid Wheat Yield Trials.

The International Maize and Wheat Improvement Center (CIMMYT) annually distributes advanced wheat (Triticum aestivum L.) breeding lines to collaborators worldwide through the International Wheat Improvement Network. Lines are disseminated through international nurseries, including the Elite Spring Wheat Yield Trial (ESWYT) targeted to optimal (irrigated and high production) wheat production areas and the Semi-arid Wheat Yield Trial (SAWYT) targeted to low rainfall environments. A total of 2,184 wheat lines that formed the ESWYT and SAWYT since 1979 and 1992, respectively, were genotyped using genotyping-by-sequencing to explore trends of genetic diversity and selection footprints associated with continuous crop improvement and adaptation. Due to a small population size of each trial, adjacent year trials were pooled into subpopulations. Population structure was evaluated using discriminant analysis of principal components and fixation index. High levels of admixture within and across the ESWYT and SAWYT subpopulations were revealed, indicating that the entire genetic diversity in the overall CIMMYT germplasm pool is harnessed to target core traits to individual mega-environments. Genome wide scans of deviations of minor allele frequencies at each marker identified large linkage blocks in several chromosomes. The scans also revealed that 9.8 and 2.0% of the SNP markers could be associated to selection signatures over time and to environmental adaptation (significant deviations between ESWYT and SAWYT), respectively. Several known genes and previously identified haplotypes associated with grain yield in more recent CIMMYT elite germplasm did fall into genomic regions with directional selection.

Plant diseases, global food security and the role of R. Glenn Anderson

R. Glenn Anderson was Norman Borlaug’s ‘green fingered agricultural scientist’ and a humanitarian who captained the wheat revolution in India during the 1960s. Afterwards, he directed the CIMMYT International Wheat Program where he was instrumental in establishing increased wheat disease surveys, broadening of the wheat genetic diversity for adaptation and disease resistance. He institutionalized multi-location yield and disease testing/analysis and regional breeding programmes, as well as strengthening the training of young scientists. Aspects of his work and other issues will be discussed in relation to present day global food security.

Скрининг сортов яровой мягкой пшеницы питомника Касиб к бурой и стеблевой ржавчине в условиях Западной Сибири

In connection with climate warming and, consequently, the deterioration of phytopathological situation, associated with the emergence of aggressive races of fungal diseases, as well as the cultivation of susceptible varieties on the main wheat sowing area in Western Siberia, it is important to expand the genotypic variety of wheat varieties and to search for new sources of long-term sustainability. The results of the assessment of spring soft wheat varieties of the KASIB breeding nursery, set up jointly by the scientific institutions of Western Siberia, Kazakhstan and CIMMYT International Center for the Improvement of Corn and Wheat are presented in the conditions of the southern forest-steppe of West Siberia. The research was conducted in 2011-2016, using field and laboratory methods. The results of the assessment of susceptibility of KASIB varieties to brown and stem rust have shown, that varieties with high resistance prevail among resistant varieties in all phases of plant development, which indicates targeted selection for immunity with genes of race-specific and age resistance. The use of cluster analysis made it possible to identify significant differences in productivity and resistance to rust diseases of the varieties of KASIB program. Wheat varieties from KASIB are underlined: 14, 15 - Lutestsens 141/03-2 and Sigma (SibNIISKh), from KASIB nursery 16, 17 - Erytrospermum 85-08 (Omsk SAU), Lutestsens 6/04-4 and Lutestsens 186/04- 61 (SibNIISKh), resistant to brown and stem rust, exceeding in terms of yield standards, which are recommended to be used as a starting material for wheat selection in Western Siberia.

Genetic Yield Gains In CIMMYT's International Elite Spring Wheat Yield Trials By Modeling The Genotype × Environment Interaction.

We calculated the annual genetic gains for grain yield (GY) of wheat (Triticum aestivum L.) achieved over 8 yr of international Elite Spring Wheat Yield Trials (ESWYT), from 2006–2007 (27th ESWYT) to 2014–2015 (34th ESWYT). In total, 426 locations were classified within three main megaenvironments (MEs): ME1 (optimally irrigated environments), ME4 (drought-stressed environments), and ME5 (heat-stressed environments). By fitting a factor analytical structure for modeling the genotype × environment (G × E) interaction, we measured GY gains relative to the widely grown cultivar Attila (GYA) and to the local checks (GYLC). Genetic gains for GYA and GYLC across locations were 1.67 and 0.53% (90.1 and 28.7 kg ha–1 yr–1), respectively. In ME1, genetic gains were 1.63 and 0.72% (102.7 and 46.65 kg ha–1 yr–1) for GYA and GYLC, respectively. In ME4, genetic gains were 2.7 and 0.41% (88 and 15.45 kg ha–1 yr–1) for GYA and GYLC, respectively. In ME5, genetic gains were 0.31 and 1.0% (11.28 and 36.6 kg ha–1 yr–1) for GYA and GYLC, respectively. The high GYA in ME1 and ME4 can be partially attributed to yellow rust races that affect Attila. When G × E interactions were not modeled, genetic gains were lower. Analyses showed that CIMMYT’s location at Ciudad Obregon, Mexico, is highly correlated with locations in other countries in ME1. Lines that were top performers in more than one ME and more than one country were identified. CIMMYT’s breeding program continues to deliver improved and widely adapted germplasm for target environments.

Evaluating Testing Strategies for Plant Breeding Field Trials: Redesigning a CIMMYT International Wheat Nursery

ABSTRACTGenotypes produced from plant breeding programs for annual crops are evaluated in multiyear, multilocation field trials where a large number of genotypes grown in a few locations in the first year are progressively reduced by selection and tested in a greater number of locations in successive years. Provided fixed resources are specified, the efficiencies of testing strategies differing in the number of locations and replications used and in the number of genotypes tested in successive years can be evaluated by three statistics (genetic repeatability, acceptance probability, and potential gain) calculated from five variance components applicable to the field trials. The five variance components required are deployed genetic variance, genotype‐by‐year, genotype‐by‐location, and genotype‐by‐year‐by‐location interaction variances and the residual (error) variance. Strictly, known variance components are required, but the statistics and their standard errors can be calculated using robust estimates of the variance components obtained from a combined analysis over years of a large set of historical data from field trials that are connected by shared genotypes across years, as genotype‐by‐year and genotype‐by‐year‐by‐location variance components are estimable. Single‐year analyses are unsuitable, as no estimate of the interactions with year are available, and such analyses produce biased estimates of genetic variance and genotype‐by‐location interaction variance. These procedures are illustrated using an example from the CIMMYT international wheat breeding program to evaluate 2‐yr testing strategies for CIMMYT's Elite Spring Wheat Yield Trials that has been distributed and evaluated internationally since 1979.

Genetic Yield Gains of the CIMMYT International Semi‐Arid Wheat Yield Trials from 1994 to 2010

ABSTRACTGenetic progress for yield has been assessed globally in the semi‐arid wheat yield trials (SAWYTs) of the International Maize and Wheat Improvement Center (CIMMYT) over a 17‐yr period. Grain yield expressed as a percentage of the long‐term check cultivar Dharwar Dry has increased at approximately 1% yr−1 between 1994 and 2010. In real terms, yield has been increased at a rate of 31 kg ha−1 yr−1. The rate of yield increase in high‐yielding environments was twice that of low‐yielding environments. The average yield of low‐yielding sites are significantly correlated with the average yield of high‐yielding sites (p < 0.001), and many of the highest‐yielding lines of the various SAWYT performed well at both low‐ and high‐yielding sites. The key parents Attila and Pastor were consistently high yielding in several of the early SAWYT. In later trials their derivatives were also high yielding. The line Vorobey, developed by crossing Pastor with a synthetic derivative, showed outstanding yield in SAWYT 11 and 12. The performance of CIMMYT lines compared to local check cultivars was relatively stable over time. A success rate was calculated as the ratio of the number of sites where a given line is superior to the local check divided by the total number of sites. On average, the success rate of the 10% best lines was 61% in low‐yielding sites and 62% in high‐yielding sites.

A Collection of Popcorn as a Reservoir of Genes for the Generation of Lineages

In the present study, we analyze the genetic structure and diversity among accessions of popcorn obtained from the CIMMYT International Maize and Wheat Improvement Center that represent the diversity available for current use by breeding programs. The main objectives were to identify SSR loci that were the best indicators of genetic diversity, to measure the genetic diversity within popcorn genotypes, and to analyze the genetic structure of the promising populations destined for use in breeding programs. The mean gene diversity of all SSR loci was 0.6352. An extremely high population differentiation level was detected (F(st) = 0.3152) with F(st) for each locus ranging from 0.1125 (Umc1229) to 0.4870 (Umc1755). Analyzing the genetic structure of eight popcorn accessions was especially important for identifying both SSR loci with high levels of heterozygosity and genotypes showing high heterozygosity (BOYA462 and ARZM13 050). This analysis should be the medium and long-term selection goal for the generation of inbred lines and the future production of new cultivars. Plant accessions ARZM05 083, ARZM13 050, and URUG298 may also be useful varieties that exhibit important agronomic characteristics that can be used through crosses to broaden the genetic basis of popcorn.

Components of partial disease resistance detected using a detached leaf assay in CIMMYT Fusarium head blight resistant wheat germplasm

One hundred and nineteen entries from the CIMMYT International Wheat and Maize Improvement Centre 2004/05 Fusarium head blight (FHB) resistance screening nursery were evaluated as possible sources of novel components of partial disease resistance (PDR), against FHB and Microdochium nivale snow mould, detected using a detached leaf assay. In addition the FHB resistant cvs Arina, Alsen and Frontana and 21 European wheat genotypes were included for comparison. There was wide variation among CIMMYT entries for the PDR components incubation period, latent period and lesion length (P < 0.001) and European lines for incubation and latent periods (P < 0.001). The CIMMYT entries with the longest latent periods were not superior to cv. Arina, the best European source of this PDR component identified to date. Notably the CIMMYT lines exhibiting the longest latent periods had Aegilops squarrosa (878) in their pedigree, indicating that Ae. squarrosa (878) may be a source of enhanced resistance detected by latent period. Macroscopic observation suggested that the underlying mechanisms contributing to latent period may differ among the CIMMYT germplasm and European sources of long latent period such as cv. Arina. Among the CIMMYT germplasm, incubation period was only weakly correlated with latent period (r = 0.25; P < 0.01); this also was the case among European genotypes (r = 0.36; P < 0.05) supporting previous findings that these PDR components are largely under separate genetic control. However, the correlation was higher on a subset of the most resistant and susceptible lines for latent period (r = 0.73 and r = 0.44; incubated at 10 °C and 15 °C, respectively). While a number of the European lines had latent periods that were comparable to cv. Arina many were significantly shorter indicating potential for improvement in this PDR component. Adaptations to the experimental design utilized in the present experiments for the efficient evaluation of large numbers of genotypes utilizing the detached leaf assay are discussed.

Carbon isotope discrimination and grain yield for three bread wheat germplasm groups grown at different levels of water stress

Carbon isotope discrimination (Δ), yield and other characters were determined for 75 spring bread wheat cultivars and advanced breeding lines in which water availability was varied using a line-source irrigation system. The experiment was carried out in 1989/90 at CIMMYT-CIANO, Cd. Obregon, in northwest Mexico. Forty of the cultivars and advanced breeding lines came from CIMMYT-Mexico, twenty from ICARDA-Syria, and fifteen from CIMMYT's International Drought Trial (IDT). Considering all materials together, grain yield and Δ were markedly reduced by drought (yield declined from 4560 to 1090 kg ha −1, Δ from 16.9 to 14.0‰, from least to most stressed, respectively). For each group of lines, grain yield was positively correlated with Δ in both the most stressed and least stressed parts of the trial (except for the CIMMYT lines under low stress where the correlation was nonsignificant). In addition, high yield under stress was associated with an early maturity score and with less reduction in mature plant height. Δ may be potentially used to augment selection for high yield based on yield itself, in both low- and high-stressed environments. In the latter environment, early maturity and minimal reduction in plant height should also be considered in a selection program especially under conditions of mid-season to terminal drought and/or heat stress.

Variation in quality characteristics associated with some spring 1B/1R translocation wheats

Advanced lines (295) from CIMMYT's International Bread Wheat Screening Nursery, a large proportion of which carry the 1B/1R translocation, were examined in terms of their sodium dodecyl sulfate (SDS)-sedimentation volumes and Alveograph characteristics, as well as their dough mixing and bread-making properties. A significant quality trait variability was observed for all parameters evaluated. Comparison of sister lines with and without the 1B/1R translocation showed that variations in SDS-sedimentation volume. Alveograph characteristics, dough mixing and baking properties cannot be attributed exclusively to the presence of the 1B/1R translocation. Finally, the poor breadmaking properties, particularly dough stickiness, associated with one Mexican (Glennson 81) and two Australian (QT-2870 and SUN-89D) cultivars could not be confirmed when doughs were mixed under medium-speed mixing conditions. Therefore, the dough stickiness problem seems to be an attribute restricted mainly to high-speed mixing conditions characteristic of some modern breadmaking processes.