Posts Tagged ‘wheat’

Nutrient management and use efficiency in wheat systems of South Asia

Posted by Carelia Juarez on , in Journal Articles

Published in Advances in Agronomy  125 : 171-259, 2014

Jat, M.L.; Bijay-Singh; Gerard, B.

With the advent of Green Revolution era in the mid-1960s, high-yielding wheat (Triticum aestivum L.) varieties and chemical fertilizers were introduced in South Asia. Fertilizer consumption is continuously increasing since then, but the productivity of wheat is relatively stagnant during the last decade. In South Asia, fertilizers have been applied to wheat as blanket recommendations for regions with similar climate and landform. There exists a large variation in nutrient use efficiencies in wheat because of following blanket recommendations for nitrogen, phosphorus, and potassium in fields differing greatly in nutrient-supplying capacity of the soil. Research carried out in South Asia suggests that further improvement in nutrient use efficiency will become possible by balanced use of nitrogen, phosphorus, and potassium fertilizers, and by rational use of organic manures in wheat systems. Long-term fertility experiments also confirm the need of balanced use of nutrients to produce high sustainable yield levels of wheat. In saline alkali soils, wheat needs to be supplied with higher amounts of nutrients, particularly N, than in normal soils. Band placement of fertilizers, particularly phosphorus, leads to improved fertilizer use efficiency, but appropriate machinery is lacking. Recently introduced site-specific nutrient management strategies for wheat take into account field-to-field variability and can help increase fertilizer use efficiency more than that achieved by following blanket fertilizer recommendations. Conservation agricultural practices consisting of reduced tillage and residue retention in wheat fields have already been introduced in South Asia. Nutrient management strategies for these wheat-growing environments are also being actively worked out. Yield gap analysis shows that productivity of wheat as well as nutrient use efficiencies can be further improved.

Traits associated with winter wheat grain yield in Central and West Asia

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Integrative Plant Biology, 2014

Lopes, M.S.; Saglam, H.D.; Ozdogan, M.;Reynolds, M.P.

Improved adaptation of winter wheat to drought and heat may be influenced by days to heading, plant height, biomass, canopy temperature at grain filling, and rate of senescence. This study shows that, under supplemental irrigation or rainfed conditions, days to heading and plant height together explain up to 68% of grain yield variation, and these associations were further confirmed in several locations across West and Central Asia. Days to heading can be slightly reduced below that of check line Karahan to further improve grain yield while avoiding the effect of late frosts. Plant height has been decreased in recent germplasm, but further reductions below that of check line Karahan could still improve grain yield in a wide range of environments. However, in Iranian sites taller genotypes showed better adaptation with higher biomass and increased reserves for grain filling. Canopy temperature and rate senescence were not associated with grain yield. A normalized difference vegetation index, used to estimate biomass (Feekes stages 4–5), had intermediate heritability across environments and correlated positively with grain yield under low plant density and should be explored further as a tool for early selection.

Does low yield heterosis limit commercial hybrids in wheat?

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Agricultural Research 8 (50) : 6663-6669, 2013

Sharma, R.K.

Heterosis has contributed to productivity gains in several crops like maize, rice, sorghum, cotton etc. Wheat breeders have largely been unsuccessful to take advantage from this technology at commercial level. Lack of commercial level yield heterosis is regarded as a major reason for this failure as compared to other technical barriers like difficult pollination control and seed production. The allopolyploidy nature of wheat endows even wheat purelines with a fixed intergenomic heterosis which perhaps is the foremost reason for lack of classical yield heterosis in wheat. The coming together of three diverse but functionally similar genomes causes differential gene expression among several other outcomes and leads to a diploid behaving self-sustaining intergenomic hybrid. A long history of highly successful pureline breeding and shortage of nicking parents are other two reasons responsible for failure to realize commercial level heterosis in wheat. Molecular biology tools now make it possible to dissect the phenomenon of heterosis into detectable Mendelian factors to tailor nicking parents to develop commercially sustainable wheat hybrids. This review probes the reasons for the absence of commercial-scale heterosis in wheat.

Reaction of some of Afghanistan’s wheat varieties to yellow rust under natural conditions

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Agricultural Research 8 (14) : 1255-1257, 2013

Ahmadzada, Z.;Obaidi, M.Q.; Ghanizada, A.G.; Mashook, M.; Azmatyar, M.H.; Jan, A.; Qayum, A.; Mohmand, E.; Sharma, R.K.

Afghanistan grows wheat at about 2.5 million ha, about 45% of which is irrigated. The country is not wheat sufficient and has been importing to meet domestic needs. Yellow rust is the most important disease of wheat in Afghanistan. Country has been able to manage wheat rusts mainly by having a survey surveillance system in place and by releasing resistant varieties. A total of 30 wheat varieties released during last two decades were screened for rust resistance under natural epiphytotic conditions. The rust reaction observed on two dates at one week interval revealed very fast increase in yellow rust infection. A large number of varieties e.g., Gul-96, Pamir-94, Ghori-96, HD2285 etc., were found to have very high yellow rust scores warranting their removal from seed chain.

An assessment of wheat yield sensitivity and breeding gains in hot environments

Posted by Carelia Juarez on , in Journal Articles

Published in Proceedings of the Royal Society B: Biological Sciences 280 (1752) : 1-8, 2013

Gourdji, S.M.; Mathews, K.L.;Reynolds, M.P.; Crossa, J.; Lobell, D.B.

Genetic improvements in heat tolerance of wheat provide a potential adaptation response to long-term warming trends, and may also boost yields in wheat-growing areas already subject to heat stress. Yet there have been few assessments of recent progress in breeding wheat for hot environments. Here, data from 25 years of wheat trials in 76 countries from the International Maize and Wheat Improvement Center (CIMMYT) are used to empirically model the response of wheat to environmental variation and assess the genetic gains over time in different environments and for different breeding strategies. Wheat yields exhibited the most sensitivity to warming during the grain-filling stage, typically the hottest part of the season. Sites with high vapour pressure deficit (VPD) exhibited a less negative response to temperatures during this period, probably associated with increased transpirational cooling. Genetic improvements were assessed by using the empirical model to correct observed yield growth for changes in environmental conditions and management over time. These ‘climate-corrected’ yield trends showed that most of the genetic gains in the high-yield-potential Elite Spring Wheat Yield Trial (ESWYT) were made at cooler temperatures, close to the physiological optimum, with no evidence for genetic gains at the hottest temperatures. In contrast, the Semi-Arid Wheat Yield Trial (SAWYT), a lower-yielding nursery targeted at maintaining yields under stressed conditions, showed the strongest genetic gains at the hottest temperatures. These results imply that targeted breeding efforts help us to ensure progress in building heat tolerance, and that intensified (and possibly new) approaches are needed to improve the yield potential of wheat in hot environments in order to maintain global food security in a warmer climate.

Genome-wide association mapping of yield and yield components of spring wheat under contrasting moisture regimes

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics, 2013

Edae, E.A.; Byrne, P.F.; Haley, S.D.; Lopes, M.S.; Reynolds, M.P.

Genome-wide association mapping has become a widespread method of quantitative trait locus (QTL) identification for many crop plants including wheat (Triticum aestivum L.). Its benefit over traditional bi-parental mapping approaches depends on the extent of linkage disequilibrium in the mapping population. The objectives of this study were to determine linkage disequilibrium decay rate and population structure in a spring wheat association mapping panel (n = 285–294) and to identify markers associated with yield and yield components, morphological, phenological, and drought tolerance-related traits. The study was conducted under fully irrigated and rain-fed conditions at Greeley, CO, USA and Melkassa, Ethiopia in 2010 and 2011 (five total environments). Genotypic data were generated using diversity array technology markers. Linkage disequilibrium decay rate extended over a longer genetic distance for the D genome (6.8 cM) than for the A and B genomes (1.7 and 2.0 cM, respectively). Seven subpopulations were identified with population structure analysis. A stable QTL was detected for grain yield on chromosome 2DS both under irrigated and rain-fed conditions. A multi-trait region significant for yield and yield components was found on chromosome 5B. Grain yield QTL on chromosome 1BS co-localized with harvest index QTL. Vegetation indices shared QTL with harvest index on chromosome 1AL and 5A. After validation in relevant genetic backgrounds and environments, QTL detected in this study for yield, yield components and drought tolerance-related traits may be used in marker-assisted selection in wheat breeding programs.

Crops that feed the world 10. Past successes and future challenges to the role played by wheat in global food security

Posted by Carelia Juarez on , in Journal Articles

Published in Food Security 5 (3) : 291-317, 2013

Shiferaw, B.; Smale, M.; Braun, H.J.; Duveiller, E.; Reynolds, M.P.; Muricho, G.

Wheat is fundamental to human civilization and has played an outstanding role in feeding a hungry world and improving global food security. The crop contributes about 20 % of the total dietary calories and proteins worldwide. Food demand in the developing regions is growing by 1 % annually and varies from 170 kg in Central Asia to 27 kg in East and South Africa. The developing regions (including China and Central Asia) account for roughly 53 % of the total harvested area and 50 % of the production. Unprecedented productivity growth from the Green Revolution (GR) since the 1960s dramatically transformed world wheat production, benefitting both producers and consumers through low production costs and low food prices. Modern wheat varieties were adopted more rapidly than any other technological innovation in the history of agriculture, recently reaching about 90 % of the area in developing regions. One of the key challenges today is to replace these varieties with new ones for better sustainability. While the GR “spared” essential ecosystems from conversion to agriculture, it also generated its own environmental problems. Also productivity increase is now slow or static. Achieving the productivity gains needed to ensure food security will therefore require more than a repeat performance of the GR of the past. Future demand will need to be achieved through sustainable intensification that combines better crop resistance to diseases and pests, adaptation to warmer climates, and reduced use of water, fertilizer, labor and fuel. Meeting these challenges will require concerted efforts in research and innovation to develop and deploy viable solutions. Substantive investment will be required to realize sustainable productivity growth through better technologies and policy and institutional innovations that facilitate farmer adoption and adaptation. The enduring lessons from the GR and the recent efforts for sustainable intensification of cereal systems in South Asia and other regions provide useful insights for the future.

Doubled haploids versus conventional breeding in CIMMYT wheat breeding programs

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science 53 (1) : 74-83, 2013

Huihui Li; Singh, R.P.;Braun, H.J.; Pfeiffer, W.H.; Jiankang Wang

Doubled haploid (DH) technology has been used in breeding programs for several decades and is currently the method of choice in a number of crop species, including barley (Hordeum vulgare L.), rapeseed (Brassica napus L.), maize (Zea mays L.), and wheat (Triticum aestivum L.). In this study we investigated via computer simulation the benefit of using DHs compared with the conventional wheat breeding strategy used at CIMMYT. Two strategies using DHs were considered: DH lines directly derived from F1 hybrids (F1–DH), and DH lines derived from F3 individuals that are retained following selection for agronomic traits in the F2 generation (F3–DH). Genetic gains per cycle, per year, and per dollar spent were consistently higher for conventional breeding than for DH breeding strategies, especially gains per dollar. Though the F1–DH strategy saved 1 yr in completing a breeding cycle, genetic gains per year for the adaptation trait from F1–DH were much lower than those from conventional breeding, where two growing seasons are used per year. Though the DH breeding strategy showed no significant advantages over the conventional wheat shuttle-breeding regime of CIMMYT, we did not exclude the possibility that the DH breeding strategy may have advantages when genetic gains per unit of time are considered, and only one generation is grown per year. The conventional shuttle regime will continue to be the major wheat breeding strategy at CIMMYT, where two cycles can be grown per year and breeders can do selection in large populations in both cycles.

Identification of genetic resistance to cereal cyst nematodes; Heterodera avenae (Wollenweber, 1924), Heterodera filipjevi (Madzhidov, 1981) Stelter and Heterodera latipons (Franklin, 1969) in some international bread wheat germplasms

Posted by Carelia Juarez on , in Journal Articles

Published in Turkiye Entomoloji Dergisi – Turkish Journal  of Entomology 37 (3) : 277-282, 2013

Imren, M.; Toktay, H.; Bozbuga, R.; Erginbas Orakci, G.; Dababat, A.; Elekcioglu, I.H.

The cereal cyst nematodes, Heterodera avenae group, are known as parasites of cereals worldwide. In Turkey, the cereal cyst nematodes, Heterodera filipjevi, H. avenae and H. latipons, are the three known species infested wheat fields and cause high yield losses. The using of resistance varieties is one of the most effective methods for controlling cereal cyst nematodes. Recently, resistance genes (Cre genes) which are obtained from wild wheat genotypes have been transferred into bread wheat varieties to control the cereal cyst nematodes species. In this study, the efficiency of some sources of resistance (CreR, Cre1, Cre2, Cre3, Cre7 and Cre8) in wheat against some Turkish H. avenae, H. filipjevi and H. latipons populations was investigated in-vitro conditions. According to results, the effect of resistance genes showed variation depending on different Cereal cyst nematode populations; H.avenae, H. filipjevi and H. latipons. Although Cre1 gene was only found as completely resistant to all (three) nematode species, Cre3 and Cre7 were found resistant to H. avenae and H. latipons. Cre R was also determined as resistant to H. filipjevi and H. latipons populations but Cre8 was only found resistant against to H. filipjevi population. No resistance was found in Cre 2 gene against to all nematode populations. Additionally, 2 resistance gene-free variety and lines were found resistant to H. avenae; 3 wheat lines to H. filipjevi and 11 wheat genotypes were found moderately resistant to H. latipons.

International Gluten Workshop, 11. Proceedings. Beijing, China; 12-15 Aug. 2012

Posted by Carelia Juarez on , in CIMMYT Publications

International Gluten Workshop, 11. Proceedings. Beijing, China; 12-15 Aug. 2012. 2013. He Zhonghu; Daowen Wang. : ix, 212 p.. Mexico, DF (Mexico). CIMMYT.

98165.pdfThe 11th International Gluten Workshop would not have been possible without the valuable  contributions of the Organizing Committ ee. I would like to sincerely acknowledge the advice and  help of my committ ee colleagues: Xu Liu, CAAS, China; Rudi Appels, Murdoch University, Australia;  Roberto Javier Pena and Hans-Joachim Braun, CIMMYT, Mexico; Gerard Branlard, INRA, France;  Craig Morris and Susan Altenbach, USDA-ARS, USA; T.M. Ikeda, NARO, Japan; W. John Rogers,  Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina; Wujun Ma, Western  Australia Department of Agriculture and Food, Australia; Domenico Lafi andra, University of Tuscia,  Italy; Perry K. W. Ng, Michigan State University, USA; Shunhe Cheng, Yangzhou Agricultural  Research Institute, China; Aimin Zhang, CAS, China; Xianchun Xia, CAAS, China; Yueming Yan,  Capital Normal University, China; and Daowen Wang, CAS, China.

Many committ ee members also chaired sessions along with scientists listed below: Angela Juhasz,  Hungarian Academy of Sciences, Hungary; Guangyuan He, Huazhong University of Science and  Technology, China; Frank Bekes, FBFD PTY LTD, Australia; Yimin Wei, CAAS, China; and Tuula  Songtag-Strohm, University of Helsinki, Finland. I am also very grateful to Aimin Zhang and his staff  at the Institute of Genetics and Developmental Biology, CAS, and Na Zhang, Simin Li, Yonggui Xiao,  Yong Zhang, and Yan Zhang at the Institute of Crop Science, CAAS, for organizing the visit to the  wheat labs in these two institutes and for other logistical support.

Financial support was generously provided by the National Natural Science Foundation of China  (NSFC, 31210303039), National Basic Research Program on Genetic Studies of Wheat Agronomic  Traits and Varietal Improvement (2009Cb11830) from the Ministry of Science and Technology, and the  International Collaboration Program (2011-G3) from the Ministry of Agriculture. I also particularly  wish to acknowledge the participation, exhibition and fi nancial contributions of Brabender, Chopin  Technologies, and Perten in this workshop.

This workshop would not have been possible without administrative support from the Institute of  Crop Science, CAAS, the Institute of Genetics and Developmental Biology, CAS, and CIMMYT. Finally, I am sure all authors and the organizing committ ee join with me in giving special thanks  to Professor Robert McIntosh for editing the manuscripts included in these proceedings, and to the  CIMMYT editorial team for design and printing