Posts Tagged ‘Euphytica’

Low-nitrogen stress tolerance and nitrogen agronomic efficiency among maize inbreds: comparison of multiple indices and evaluation of genetic variation

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Published in Euphytica 180(2) 281-290 2011 

Low-nitrogen stress tolerance and nitrogen agronomic efficiency among maize inbreds: comparison of multiple indices and evaluation of genetic variation

Yongshen Wu, Wenguo Liu, Xinhai Li, Mingshun Li, Degui Zhang, Zhuanfang Hao, Jianfeng Weng, Yunbi Xu, Li Bai and Shihuang Zhang, et al.

Limited information is available on genetic variation in low-nitrogen (low-N) stress tolerance and N-use efficiency (NUE) among maize inbreds. To unveil this information, a panel of 189 diverse maize inbred lines was evaluated under contrasting levels of N availability over 2 years. Low-N agronomic efficiency (LNAE), absolute grain yield (GY) at low-N conditions, and the ratio between GY at low-N and optimum-N conditions were taken into account to represent low-N tolerance. Additionally, N-agronomic efficiency (NAE) along with other agronomic traits was also analyzed. Analysis of variance revealed significant effects of genotype on LNAE, NAE, and GY. The estimated broad-sense heritability was 0.38 for LNAE while it was only 0.11 for NAE, implying that selection based on LNAE should be more effective than NAE. LNAE exhibited highly positive genotypic and phenotypic correlations with GY, ear kernel number (EKN), kernel weight, plant height (PH), and chlorophyll content at low-N conditions, while it was negatively correlated with grain-N content and anthesis-silking interval. Path analysis indicated that the EKN at low-N stress had the highest positive effects on LNAE.

Genetic protection of wheat from rusts and development of resistant varieties in Russia and Ukraine

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Published in Euphytica 179(2): 297-311, 2011

Genetic protection of wheat from rusts and development of resistant varieties in Russia and Ukraine

A. Morgounov, I. Ablova, O. Babayants, L. Babayants, L. Bespalova, Zh. Khudokormov, N. Litvinenko, V. Shamanin and V. Syukov

Leaf rust represents the major threat to wheat production in Russia and Ukraine. It has been present for many years and epidemics of the pathogen occur in different regions on both winter and spring wheat. In some regions there is evidence of more frequent epidemics, probably due to higher precipitation as a result of climate change. There is evidence that the virulence of the leaf rust population in Ukraine and European Russia and on winter wheat and spring wheat is similar. The pathogen population structure in Western Siberia is also similar to the European part, although there are some significant differences based on the genes employed in different regions. Ukrainian wheat breeders mostly rely on major resistance genes from wide crosses and have succeeded in developing resistant varieties. The North Caucasus winter wheat breeding programs apply the strategy of deploying varieties with different types of resistance and genes. This approach resulted in decreased leaf rust incidence in the region. Genes Lr23 and Lr19 deployed in spring wheat in the Volga region were rapidly overcome by the pathogen. There are continuing efforts to incorporate resistance from wild species. The first spring wheat leaf rust resistant varieties released in Western Siberia possessed gene LrTR which protected the crop for 10–15 years, but was eventually broken in 2007. Slow rusting is being utilized in several breeding programs in Russia and Ukraine, but has not become a major strategy.

Global status of wheat leaf rust caused by Puccinia triticina

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Published in Euphytica 179(1): 143-160

Global status of wheat leaf rust caused by Puccinia triticina

J. Huerta-Espino, R. P. Singh, S. Germán, B. D. McCallum, R. F. Park, W. Q. Chen, S. C. Bhardwaj and H. Goyeau

Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.

http://www.springerlink.com/content/p141qxvwm4q7u4r3/

Improving wheat stripe rust resistance in Central Asia and the Caucasus

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Published in Euphytica 179 (1); 197-207, 2011

Improving wheat stripe rust resistance in Central Asia and the Caucasus

Z. M. Ziyaev, R. C. Sharma, K. Nazari, A. I. Morgounov, A. A. Amanov, Z. F. Ziyadullaev, Z. I. Khalikulov and S. M. Alikulov

Wheat is the most important cereal in Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and the Caucasus (Armenia, Azerbaijan and Georgia). Stripe rust, caused by Puccinia striiformis f. sp. tritici is considered the most important disease of wheat in Central Asia and the Caucasus (CAC). Although stripe rust has been present in the region for a long time, it has become a serious constraint to wheat production in the past 10 years. This is reflected by the occurrence of five epidemics of stripe rust in the CAC region since 1999, the most recent in 2010. Several wheat varieties occupying substantial areas are either susceptible to stripe rust or possess a low level of resistance. Information on the stripe rust pathogen in terms of prevalent races and epidemiology is not readily available. Furthermore, there is an insufficient understanding of effective stripe rust resistance genes in the region, and little is known about the resistance genes present in the commercial varieties and advanced breeding lines. The deployment of resistant varieties is further complicated by putative changes in virulence in the pathogen population in different parts of the CAC. Twenty four out of 49 improved wheat lines received through international nurseries or other exchange programs showed high levels of resistance to stripe rust to local pathogen populations in 2009. Fifteen of the 24 stripe rust resistant lines also possessed resistance to powdery mildew. It is anticipated that this germplasm will play an important role in developing stripe rust resistant wheat varieties either through direct adoption or using them as parents in breeding programs.

http://www.springerlink.com/content/3858251175855787/

Race non-specific resistance to rust diseases in CIMMYT spring wheats

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Published in Euphytica 179(1); 175-186, 2011

Race non-specific resistance to rust diseases in CIMMYT spring wheats

R. P. Singh;   J. Huerta-Espino;  S. Bhavani; S. A. Herrera-Foessel; D. Singh; P. K. Singh; G. Velu;  R. E. Mason; Y. Jin; P. Njau; J. Crossa

Rust diseases continue to cause significant losses to wheat production worldwide. Although the life of effective race-specific resistance genes can be prolonged by using gene combinations, an alternative approach is to deploy varieties that posses adult plant resistance (APR) based on combinations of minor, slow rusting genes. When present alone, APR genes do not confer adequate resistance especially under high disease pressure; however, combinations of 4–5 such genes usually result in “near-immunity” or a high level of resistance. Although high diversity for APR occurs for all three rusts in improved germplasm, relatively few genes are characterized in detail. Breeding for APR to leaf rust and stripe rust in CIMMYT spring wheats was initiated in the early 1970s by crossing slow rusting parents that lacked effective race-specific resistance genes to prevalent pathogen populations and selecting plants in segregating populations under high disease pressure in field nurseries. Consequently most of the wheat germplasm distributed worldwide now possesses near-immunity or adequate levels of resistance. Some semidwarf wheats such as Kingbird, Pavon 76, Kiritati and Parula show high levels of APR to stem rust race Ug99 and its derivatives based on the Sr2-complex, or a combination of Sr2 with other uncharacterized slow rusting genes. These parents are being utilized in our crossing program and a Mexico-Kenya shuttle breeding scheme is used for selecting resistance to Ug99. High frequencies of lines with near-immunity to moderate levels of resistance are now emerging from these activities. After further yield trials and quality assessments these lines will be distributed internationally through the CIMMYT nursery system.

http://www.springerlink.com/content/c0gm557225003551/

Delivering rust resistant wheat to farmers: a step towards increased food security

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Published in Euphytica 179(1): 187-196, 2011

Delivering rust resistant wheat to farmers: a step towards increased food security

 A. K. Joshi; M. Azab;  M. Mosaad;  M. Moselhy;  M. Osmanzai; S. Gelalcha; G. Bedada; M. R. Bhatta; A. Hakim; P. K. Malaker; M. E. Haque;  T. P. Tiwari;  A. Majid; M. R. Jalal Kamali;  Z. Bishaw; R. P. Singh;  T. Payne;  H. J. Braun

An important step towards reducing the vulnerability of wheat in Africa and Asia to the Ug99 race of the stem rust pathogen is the substitution of current susceptible varieties with superior resistant varieties. In the 2008–2009 cropping season both seed multiplication and dissemination of Ug99 resistant varieties were initiated in Afghanistan, Bangladesh, Egypt, Ethiopia, Iran, India, Nepal and Pakistan. Ug99 resistant varieties must occupy about 5% of the area sown to wheat in each country to ensure sufficient seed to displace current popular varieties. Because of the underdeveloped seed industry and small farm sizes in most of these countries, various strategies are being applied for rapid multiplication and dissemination of resistant varieties. Approaches being used include pre-release seed multiplication while candidate resistant lines are being tested in national evaluation trials and farmer participatory selection. Resistant varieties are already released in Afghanistan, Bangladesh, Egypt and Pakistan and more varieties are expected to be released in 2010 in these and other countries. Our results show that some new Ug99 resistant lines have yield superiority over dominant local varieties. Activities and progress in seed multiplication using existing and new Ug99 resistant varieties are discussed.

http://www.springerlink.com/content/t127776u3n338823/

Genetic distance and hybrid value in tropical maize under P stress and non stress conditions in acid soils

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Published in Euphytica 178(1): 99-109, 2011

Genetic distance and hybrid value in tropical maize under P stress and non stress conditions in acid soils

M. L. C. George, F. Salazar, M. Warburton, L. Narro and F. A. Vallejo

An emphasis in maize breeding for areas with acid soils is the development of varieties with tolerance to P-deficiency plus high yield potential in acidic as well as normal soils. This study was carried out to assess the (i) genetic diversity within a set of tropical inbred lines developed from acid soil-tolerant populations; (ii) F1 yield performance, mid-parent heterosis (MPH), high-parent heterosis (HPH), and specific combining ability (SCA) in a diallel set of crosses under P stress (low P) and non-stress (high P) conditions; and (iii) the effect of P stress on the relationship between genetic distance (GD) and hybrid performance. Using field evaluation and molecular marker studies, the results show that these germplasm from the South American maize breeding program of CIMMYT for improving tolerance to acid soils had only a moderate level of genetic diversity. The utility of GD as a predictor of hybrid value is best up to a certain threshold, as correlations with GD became inconsistent when the inbred parents were greatly divergent. There was no correlation between GD and F1 grain yield, MPH, HPH and SCA when the GD was >0.77. The high correlation of GD with F1 grain yield and with SCA in specific subsets of crosses having a narrower range of GD shows that GD can be put to practical use in predicting hybrid performance. The highest correlation between GD and SCA, seen in the subset of crosses between lines within a cluster, was reasonably stable even when the environment had a severe effect on yield.

Phenotypic correlations, G × E interactions and broad sense heritability analysis of grain and flour quality characteristics in high latitude spring bread wheats from Kazakhstan and Siberia

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Published in Euphytica 171(1): 23-38, 2010

Phenotypic correlations, G × E interactions and broad sense heritability analysis of grain and flour quality characteristics in high latitude spring bread wheats from Kazakhstan and Siberia

Hugo Ferney Gómez-Becerra, Aigul Abugalieva, Alexei Morgounov, K. Abdullayev, L. Bekenova, M. Yessimbekova, G. Sereda, S. Shpigun, V. Tsygankov, Yu Zelenskiy, Roberto Javier Peña and Ismail Cakmak

Grain and flour samples of 42 high latitude spring bread wheat genotypes from Kazakhstan and Siberia evaluated in a multi-location trial were analyzed for grain concentrations of protein, zinc (Zn) and iron (Fe), as well as flour quality characteristics. The genotypes showed high grain protein concentrations (14–19%), but low dough strength was a common feature for most of them. Significant positive correlations were found between grain protein and flour protein, gluten, gliadin, gli/glu ratio, Zn, and Fe contents. Grain protein was also correlated positively with hardness, sedimentation, farinograph dough development time (DDT), stability time and ash content. Grain Fe concentration was positively associated with sedimentation, stability time, water absorption and valorimeter value, suggesting that improvements in micronutrient concentrations in the grain parallels enhancement in gluten strength. Interestingly, glutenin content correlated negatively with the concentrations of grain and flour protein, gluten, and minerals; and also with gluten deformation index (IDK), DDT, and stability time. Conversely, gliadin content showed strong positive correlations with the concentrations of grain and flour protein, gluten, and minerals. Gliadin also correlated positively, but in lesser magnitude, with DDT, stability time and IDK. Environment and G×E interaction were important sources of variation for some quality characteristics. This was reflected in the low broad sense heritability (H) values for traits related to flour strength, such as sedimentation, IDK, stability time and gliadin content. Breeding strategies, including three testing locations at the advanced selection stages, are adequate for the enhancement of most of the quality traits, but faster improvement in flour strength could be achieved with a larger number of locations.

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

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Published in Euphytica 171(1): 53-64, 2010

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

Ram C. Sharma, Alexei I. Morgounov, Hans J. Braun, Beyhan Akin, Mesut Keser, David Bedoshvili, Ahmet Bagci, Christopher Martius and Maarten van Ginkel

Improved winter wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in Central and West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite winter wheat breeding lines developed by the International Winter Wheat Improvement Program (IWWIP), to analyze their stability across diverse environments, and to identify superior genotypes that could be valuable for winter wheat improvement or varietal release. One hundred and one advanced winter wheat breeding lines and four check cultivars were tested over a 5-year period (2004–2008). Grain yield and agronomic traits were analyzed. Stability and genotypic superiority for grain yield were determined using genotype and genotype × environment (GGE) biplot analysis. The experimental genotypes showed high levels of grain yield in each year, with mean values ranging from 3.9 to 6.7 t ha−1. A set of 25 experimental genotypes was identified. These were either equal or superior to the best check based on their high mean yield and stability across environments as assessed by the GGE biplot analysis. The more stable high yielding genotypes were ID800994.W/Falke, Agri/Nac//Attila, ID800994W/Vee//F900K/3/Pony/Opata, AU//YT542/N10B/3/II8260/4/JI/Hys/5/Yunnat Esskiy/6/KS82W409/Spn and F130-L-1-12/MV12. The superior genotypes also had acceptable maturity, plant height and 1,000-kernel weight. Among the superior lines, Agri/Nac//Attila and Shark/F4105W2.1 have already been proposed for release in Kyrgyzstan and Georgia, respectively. The findings provide information on wide adaptation of the internationally important winter wheat genotypes, and demonstrate that the IWWIP program is enriching the germplasm base in the region with superior winter wheat genotypes to the benefit of national and international winter wheat improvement programs.

Genetics of wheat–Pyrenophora tritici-repentis interactions

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Published in Euphytica 171(1):1-13, 2010

Genetics of wheat–Pyrenophora tritici-repentis interactions

P. K. Singh, R. P. Singh, E. Duveiller, M. Mergoum, T. B. Adhikari and E. M. Elias

Tan spot, caused by an ascomycete fungus Pyrenophora tritici-repentis, is one of the most devastating foliar diseases of wheat. This fungus induces two distinct symptoms, tan necrosis and extensive chlorosis, on susceptible wheat cultivars. Besides causing average yield losses of 5–10%, tan spot also causes significant losses in grain quality by grain shriveling, red smudge, and black point. Conservation agriculture in combination with wheat monoculture involving cultivation of susceptible cultivars has resulted in frequent onset of tan spot epidemics worldwide. Development of new resistant wheat cultivars, in conjunction with crop rotation, will provide an effective, economical, and environmentally safe means of controlling tan spot. Presently, eight races of P. tritici-repentis have been identified worldwide based on the ability to induce necrosis and chlorosis symptoms on a set of differential wheat cultivars. P. tritici-repentis is a homothallic fungus having both sexual and asexual reproduction resulting in high genetic diversity worldwide. Both quantitative and qualitative mode of inheritance for resistance to tan spot of wheat has been reported. The tan spot fungus produces multiple host-specific toxins and host resistance is highly correlated to insensitivity to toxins. Genetic studies have further confirmed that wheat–P. tritici-repentis follows the toxin model of gene-for-gene hypothesis although other mechanism of host–pathogen interaction may exist and exploitation of all resistance phenomenon is to be adopted to develop durable resistant cultivars.