International Symposium On Wheat Yield Potential - Challenges To International Wheat Breeding

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Like many other patterns, investment in research is often cyclical. International centers like CIMMYT have focused substantial resources on biotic and abiotic stresses for about two decades now, but raising total productivity is also back on the development agenda. There are a number of reasons for this, among them sharp rises in the price of staple foods as well as the manifestation of detrimental effects of climate change on productivity. Those factors threaten not only the livelihoods of resource-poor people but food security at...

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ISBN: 970-648-144-3

M.P. Reynolds, J. Pietragalla, and H.-J. Braun, Editors
International Symposium on Wheat Yield Potential: Challenges to International Wheat Breeding
CD—Symposium oral papers also published in journal special issues

Symposium sponsors: Euphytica Relationships between height and yield in near- Genetic improvement of grain yield and associated
Challenges to international wheat breeding isogenic spring wheats that contrast for major traits in the southern China winter wheat region:
Australian Centre for International Agricultural Research (ACIAR). M.P. Reynolds, H.-J. Braun, J. Pietragalla, and R. Ortiz reduced height genes S.C. Chapman, K.L. 1949 to 2000 Y. Zhou, H.Z. Zhu, S.B. Cai, Z.H. He,
Grains Research Development Corporation of Australia (GRDC). Sixty-two years of fighting hunger: Personal Mathews, R.M. Trethowan, R.P. Singh X.K. Zhang, X.C. Xia, G.S. Zhang
recollections N.E. Borlaug
International Maize and Wheat Improvement Center (CIMMYT). Partnering with farmers to accelerate adoption of Stakeholder perception of wheat production
Application of new knowledge, technologies, and new technologies in South Asia to improve wheat constraints, capacity building needs, and
strategies to wheat improvement M.E. Sorrells productivity G. Ortiz-Ferrara, A.K. Joshi, R. research partnerships in developing countries
Organizing Committee
Wheat breeding assisted by markers: CIMMYT’s Chand, M.R. Bhatta, A. Mudwari, D.B. Thapa, M.A. P. Kosina, M.P. Reynolds, J. Dixon, A. Joshi
Matthew Reynolds (Chair, scientific agenda, logistics coordination).
experience H.M. William, R. Trethowan, Sufian, T.P. Saikia, R. Chatrath, J.R. Witcombe, D.S.
Diana Godinez (administrative support and compilation of Extended Abstracts). E.M. Crosby-Galvan Virk, R.C. Sharma Journal of Agricultural Science
Rodrigo Rascón (local logistics). Yield of synthetic backcross-derived lines in rainfed Shifting undesirable correlations R.M. DePauw, Challenges to international wheat improvement
Dave Poland (communications strategy). environments of Australia F.C. Ogbonnaya, G. Ye, R.E. Knox, F.R. Clarke, H. Wang, M.R. Fernandez, M.P. Reynolds, P.R. Hobbs, and H.-J. Braun
R. Trethowan, F. Dreccer, D. Lush, J. Shepperd,
Hans Braun (consultation). J.M. Clarke, T.N. McCaig Genetic progress in yield potential in wheat: recent
M. van Ginkel The challenges of maintaining wheat productivity: advances and future prospects M.J. Foulkes,
Returns to investment in new breeding technologies Pests, diseases, and potential epidemics J.W. Snape, V.J. Shearman, M.P. Reynolds, O. Gaju,
Regional Coordination
J.P. Brennan, P.J. Martin E. Duveiller, R.P. Singh, J.M. Nicol and R. Sylvester-Bradley
Zhonghu He (China), David Bedoshvilli, Murat Karabayev, Alex Morgounov (Central Asia), High yielding spring bread wheat germplasm for global Wheat improvement in India: Present status, Prospects for increasing photosynthesis by
Olaf Erenstein, Raj Gupta, Guillermo Ortiz-Ferrara, & Stephen Waddington irrigated and rainfed production systems R.P. emerging challenges and future prospects overcoming the limitations of Rubisco
(South Asia), Ivan Ortiz-Monasterio, Julio Huerta-Espino & Javier Peña (Latin America ), Singh, J. Huerta-Espino, R. Sharma, A.K. Joshi, R. A.K. Joshi, B. Mishra, R. Chatrath, G. Ortiz-Ferrara, M.A.J. Parry, P.J. Madgwick, J.F.C. Carvalho, and
Osman Abdalla, Hans-Joachim Braun, Arne Hede, Julie Nicol, & Sanjaya Rajaram (WANA), Trethowan R.P. Singh P.J. Andralojc
High yield potential, shuttle breeding, genetic diversity, Challenges to wheat production in South Asia
Dennis Friesen (Ethiopia), Pat Wall (Zimbabwe). Improving estimation of N top-dressing by
and a new international wheat improvement strategy R. Chatrath, B. Mishra, G. Ortiz-Ferrara, S.K. Singh, addressing temporal variability in winter wheat
R. Ortiz, R. Trethowan, A.K. Joshi K. Girma, C. Mack, R. Taylor, J. Solie, D.B. Arnall,
Logistical Support
G. Ortiz-Ferrara, M. Iwanaga, J.H. Dodds, J.H. Crouch, Wheat grain yield and stability assessed through and W. Raun
Carmen Espinosa, Eleuterio Dorantes & Petr Kosina (visas). J. Crossa, H.-J. Braun regional trials in the Eastern Gangetic Plains of Sustainable improvement of wheat yield potential:
Albertina de Gracia, Teresa Rodríguez, & Arnoldo Amaya (travel & hospitality). Lessons learnt from forty years of international spring South Asia R.C. Sharma, G. Ortiz-Ferrara, The role of crop management J.K. Ransom,
Eugenio Pérez (auxiliary services). bread wheat trials R. Trethowan, J. Crossa J. Crossa, M.R. Bhatta, M.A. Sufian, J. Shoran, G.J. Endres, and B.G. Schatz
Araceli Torres, Suzuky Pinto, Vania Tellez, Gemma Molero, Dolores Vázquez & A.K. Joshi, R. Chand, G. Singh, R. Ortiz Understanding the physiological basis of yield
Carolina Saint-Pierre (registration). potential in wheat R.A. Fischer
Use of spatial analyses for global characterization of
wheat-based production systems D.P. Hodson,
Facilitation of Symposium Sessions
and J.W. White
Norman E. Borlaug (former CIMMYT Wheat Director).
Conservation agriculture: What is it and why is it
Tony Fischer (former CIMMYT Wheat Director and ACIAR sponsor representative). important for future sustainable food production?
Sanjaya Rajaram (former CIMMYT Wheat Director and ICARDA BIGM P.R. Hobbs
Program and ICWIP Director). Association of source/sink traits with yield, biomass
Masa Iwanaga, CIMMYT Director General. and radiation use efficiency among random sister
lines from three wheat crosses in a high-yield
John Dixon (CIMMYT Director, ITAU).
environment M. P. Reynolds, D. Calderini,
Jonathan Crouch (CIMMYT Director, GRU).
A. Condon, and M. Vargas
Hans Braun (CIMMYT Wheat Director).
Sink limitations to yield in wheat: How could they be
Petr Kosina (CIMMYT Training). reduced? D.J. Miralles, and G.A. Slafer
Tom Payne (CIMMYT Wheat Germplasm Bank). Structural equation modelling for studying genotype
David Poland (CIMMYT Science Writer). x environment interactions of physiological traits
affecting yield in wheat M. Vargas, J. Crossa,
M.P. Reynolds, P. Dhungana, K.M. Eskridge
Editing: Alma McNab, Mike Listman, Dave Poland
An economic assessment of the use of physiological
Design, layout, and production: Miguel Mellado, Eliot Sánchez, Marcelo Ortíz, Antonio Luna,
selection for stomatal aperture-related traits in
and Wenceslao Almazan
the CIMMYT wheat breeding programme
J.P. Brennan, A.G. Condon, M. van Ginkel, and
M.P. Reynolds
U-impact pathway for diagnosis and impact
assessment of crop improvement J. Dixon,
J. Hellin, O. Erenstein, and P. Kosina
Conservation agriculture in South Asia R. Gupta,
and K.D. Sayre
Reduced nitrogen and improved farm income for
irrigated spring wheat in the Yaqui Valley, Mexico,
using sensor-based nitrogen management
J.I. Ortiz-Monasterio, and W. Raun
International Symposium on  
Wheat Yield Potential: 
Challenges to International Wheat Breeding

M.P. Reynolds, J. Pietragalla, and H.‐J. Braun, 
CIMMYT® ( is an internationally funded, not-for-profit organization that conducts
research and training related to maize and wheat throughout the developing world. Drawing on strong
science and effective partnerships, CIMMYT works to create, share, and use knowledge and
technology to increase food security, improve the productivity and profitability of farming systems,
and sustain natural resources. Financial support for CIMMYT’s work comes from many sources,
including the members of the Consultative Group on International Agricultural Research (CGIAR)
(, national governments, foundations, development banks, and other public and private

© International Maize and Wheat Improvement Center (CIMMYT) 2008. All rights reserved. The
designations employed in the presentation of materials in this publication do not imply the expression
of any opinion whatsoever on the part of CIMMYT or its contributory organizations concerning the
legal status of any country, territory, city, or area, or of its authorities, or concerning the delimitation
of its frontiers or boundaries. CIMMYT encourages fair use of this material. Proper citation is

Correct citation: Reynolds M.P., J. Pietragalla, and H.-J. Braun, eds. 2008. International Symposium
on Wheat Yield Potential: Challenges to International Wheat Breeding. Mexico, D.F.: CIMMYT.

ISBN: 970-648-144-3

AGROVOC descriptors: Wheat; Food production; Food supply; Plant breeding; Genotype
environment interaction; Agroecosystems; Adaptation; Trials; Yields;
South Asia; Brazil; China; Ethiopia; India; Mexico; Turkey; Zimbabwe

AGRIS category codes: E10 Agricultural Economics and Policies
F30 Plant Genetics and Breeding

Dewey decimal classification: 633.1153 REY

Printed in Mexico.


v Foreword
1 International Wheat Improvement: Highlights from an Expert Symposium
M.P. Reynolds, P. Hobbs, R. Ortiz , J. Pietragalla, and H.-J. Braun

8 Stakeholders’ priorities for internationally-coordinated wheat research
M.P. Reynolds, J. Dixon, K. Ammar, P. Kosina, and H.-J. Braun

Field Day
18 A worldwide wheat research network: Highlights from field day
presentations of the international wheat yield symposium
M.P. Reynolds

Country abstracts and posters
23 Argentina
27 Azerbaijan
30 Bangladesh
35 Brazil
39 China
43 Egypt
45 Ethiopia
49 India
54 Iran
59 Kazakhstan
64 Kyrgyzstan
66 Mexico
70 Morocco
74 Nepal
79 Pakistan
82 Sudan
87 Tajikistan
91 Turkey
95 Uzbekistan
99 Zimbabwe

Oral presentations (not previously published in journal special issues)
103 Wheat yield potential
S. Rajaram, and H.-J. Braun

108 Association among durum wheat international testing sites and trends in yield
progress over the last twenty-two years
K. Ammar, J. Lage, D. Villegas, J. Crossa, H. Hernandez, and G. Alvarado

113 Using plant breeding data to move from genotype-by-environment interactions to
gene-by-environment interactions
H.A. Eagles, K. Cane, D.B. Moody, R.F. Eastwood, G.J. Hollamby, H. Kuchel, and
P.J. Martin

120 Exploitation of genetic resources through wide crosses
M. Kishii, R. Delgado, V. Rosas, A. Cortes, S. Cano, J. Sanchez, and A. Mujeeb-Kazi

126 Stomatal aperture related traits and yield potential in bread wheat
A.G. Condon, M.P. Reynolds, J. Brennan, M. van Ginkel, R. Trethowan, G.J. Rebetzke,
D.G. Bonnett, R.A. Richards, and G.D. Farquhar

134 Complementing the breeder’s eye with canopy temperature measurements
M. van Ginkel, M.P. Reynolds, R. Trethowan, E. Hernandez

136 Source and sink traits that impact on wheat yield and biomass in high production
M.P. Reynolds, J. Pietragalla, T.L. Setter, and A.G. Condon

148 Raised bed planting technologies for improved efficiency, sustainability and
K. D. Sayre, A. Limon-Ortega, and R. Gupta

161 Avenues to increase yield potential of short season, high latitude wheat in Northern
Kazakhstan and Siberia
A. Morgounov, R. Trethowan

167 Challenges to wheat production in Brazil
P.L. Scheeren, E. Caierão, M.S. Silva, A.J. Nascimento, V.R. Caetano, M.C. Bassoi,
D. Brunetta, J.C. Albrecht, W.J. Quadros, P.G. Sousa, M.G. Trindade, J.S. Sobrinho,
S. Wiethölter, and G.R. Cunha

171 Improving or preserving bread making quality while enhancing grain yield in wheat
R.J. Peña

175 Innovation systems and impact pathways for wheat
J. Dixon, J. Hellin, O. Erenstein, P. Kosina, and L.L. Nalley

181 Agricultural R&D spending at a critical crossroads
P. Pardey, J. Alston, and N. Beintema

190 Summary of evaluation questionnaire for the International Symposium on
Increasing Wheat Yield Potential
Petr Kosina

192 List of participants

On CD: Symposium oral papers also published in journal special issues


Like many other patterns, investment in research is often cyclical. International centers like
CIMMYT have focused substantial resources on biotic and abiotic stresses for about two
decades now, but raising total productivity is also back on the development agenda. There are a
number of reasons for this, among them sharp rises in the price of staple foods as well as the
manifestation of detrimental effects of climate change on productivity. Those factors threaten
not only the livelihoods of resource-poor people but food security at a broader level, as
highlighted by the World Bank’s recent World Development Report. CIMMYT has an
unsurpassed record when it comes to raising crop yields from the days of the Green Revolution;
as can be seen from the comprehensive scope of this new publication, our Global Wheat
Program is back in the game. The book consists of proceedings of a week-long consultation of
experts and leaders held in 2006 and representing all major wheat producing countries
worldwide. It encompasses their ideas on how, through internationally coordinated collaborative
research, proven technologies of the past can be married with new tools and approaches to meet
demand for the world’s number one staple crop: wheat.

Masa Iwanaga
Director General

International Wheat Improvement: Highlights
from an Expert Symposium
M.P. Reynolds, P. Hobbs, R. Ortiz , J. Pietragalla, and
H.-J. Braun

(i) Reports of a one day workshop entitled “Stakeholder
priorities for internationally-coordinated wheat
Wheat is grown on 217 million hectares throughout the research” involving representatives of major wheat
world, which produced approximately 620 million tons of producing countries on all continents whose remit was
grain annually during the period 2004-2006 (FAO, 2007) to develop: (a) a list of priorities for future wheat
and provided, on average, one-fifth of the total calorific research that could best be tackled in a globally-
input of the world’s population (FAO, 2003). In regions coordinated fashion, and (b) outlines of activities that
such as North Africa, Turkey, and Central Asia, wheat would serve as templates for future project
provides half of total dietary calories, for example, 1500 development for selected priorities (Reynolds et al. A).
(ii) The summary of field day presentations given by
kcal per capita per day in Iran. Of the cultivated wheat area,
groups of collaborating scientists in attendance
half is located in less developed countries where there have
illustrating the continuum between national, regional,
been steady increases in productivity since the green
and international-center-based research activities
revolution, associated with genetic improvements in yield
potential, resistance to diseases, adaptation to abiotic
(iii) Reports of a pre-symposium survey soliciting statistics
stresses, and better agronomic practices (Reynolds and
on wheat production and constraints to productivity
Borlaug, 2006a and b). Nonetheless, challenges to wheat
and research from 19 countries in Latin America, Sub-
production are still considerable, especially in the
Saharan Africa; Central and West Asia and North
developing world, not only because of increased demand
Africa; and South and Southeast Asia (see Country
but also because of the increased scarcity of water resources
Surveys). Collectively these countries represent over
(Shiklomanov and Rodda, 2003) ever more unpredictable
100 million ha of wheat and around 90% of the wheat
climates (Fischer et al., 2002), increased urbanization and
production in developing countries (FAO, 2006). These
loss of good quality land away from agriculture (Hobbs, on
data were also used to prepare a general summary of
CD, JAS), and decreased public sector investment in
the constraints to productivity and research across all
agriculture and rural affairs (Falcon and Naylor, 2005). To
of the above mentioned regions (Kosina et al., on CD,
meet demand in a sustainable way, more resources are
required to breed a new generation of genetically improved
cultivars as well as implement resource conserving
agronomic management practices. Summary of the Plenary Presentation

A symposium was organized by the International Maize and The symposium was opened with an address by Nobel
Wheat Improvement Center’s Global Wheat Program, with Laureate Dr. Norman Borlaug (on CD, Euphytica) entitled
support from the Australian Centre for International “Sixty-two years of fighting hunger: Personal
Agricultural Research (ACIAR), in Ciudad Obregon, recollections.” Dr. Borlaug described the evolution of
northwestern Mexico, in March 2006. The aim of this international wheat breeding including how shuttle breeding
symposium was to bring together wheat researchers was adopted in Mexico, enabling photoperiod sensitivity to
worldwide to present and discuss their ideas on how to be overcome, a pivotal step in creating internationally
address some of the pressing issues of increasing wheat adapted germplasm. His talk touched on a number of
production in a sustainable manner. Participants included historical yet topical issues, including how the 15b stem
160 scientists from over 30 wheat producing countries. rust epidemic in the US in the 1950s is being mirrored 50
Many of the ideas presented at the symposium have already years later by the virulent new race Ug99 from East Africa;
been published in 2007 (and are faithfully reproduced in the evolution of internationally coordinated public goods
this volume) in special issues of Euphytica (volume 157: 3) research in agriculture, which led to the formation of the
and Journal of Agricultural Science, Cambridge (volume CGIAR (Consultative Group of International Agricultural
145: 1-3). Highlights of these papers, along with a number Research), a system which despite its humanitarian mandate
of oral papers published for the first time in this book, are and many successes suffers from declining investment that
summarized below. In addition, this volume documents the is eroding the promise of food security for many of the
following symposium and pre-symposium activities: world’s most resource-poor people. He specifically
addressed high yield agriculture and the environment, agro-

forestry, drought tolerance, the promise of biotechnology, Value of Internationally Coordinated Breeding Efforts
bureaucracies, and fear of change, and finished with a
quote from 1949 Nobel Peace Prize winner Lord John Boyd The paper presented by Rajaram and Braun (p. 103, these
Orr, “World peace will not be built on empty stomachs.” proceedings) reviewed efforts conducted over the last 50
years to increase yield potential gains while improving
adaptation to biotic and abiotic stresses. While percent
Latest Technologies
gains have been similar in irrigated and rainfed areas in
Sorrels (on CD, Euphytica) reviewed impacts of new absolute figures, productivity has increased considerably
technologies in his article “Application of new knowledge, more in irrigated areas. Rajaram and Braun underscored the
technologies, and strategies to wheat improvement.” He need to develop new germplasm with adaptation to abiotic
highlights the complexity of the genomes of graminaceous stresses without sacrificing yield potential, so that farmers
crops and the fact that they are rapidly evolving and benefit in favorable years. A good example is Attila, a line
heterogeneous, even within species. Not surprisingly, the that has been reselected or released in countries with highly
use of marker-assisted selection for improving complex contrasting environments. They also emphasized the
traits remains one of the challenges facing wheat breeders. importance of introducing new genetic diversity. For
Progress in recent years includes new transformation example, results from Wheat International Nurseries
protocols, statistical methods, methods for characterizing distributed by CIMMYT have shown that cultivars with
environments, and equipment for phenotyping traits. Sorrels 1B/1R are better adapted to lower input conditions, and
also mentions progress in the area of molecular markers and other translocations such as 1A/1R, 7DL/7AG have already
microarray applications, gene silencing protocols, DNA shown beneficial effects on yield potential in a range of
sequencing, and transgenic crops. Comparative mapping genetic backgrounds.
and QTL studies have provided information about the
location, identity, and number of genes controlling some To meet future demands for wheat, all available
economically important traits. technologies must achieve an annual yield increase of about
2% until 2020. Singh et al. in their article “High yielding
The articles by William et al. and Ogbonnaya et al. (on spring bread wheat germplasm for global irrigated and
CD, Euphytica) review advances at the frontiers of wheat rainfed production systems” (on CD, Euphytica) report that
improvement research, namely, the use of molecular grain yields of the best new entries were 10% higher than
breeding tools and wild species for re-synthesizing wheat. the local checks in international yield trials. While not all
William et al. argue that markers are now being used to genotypes respond as well across sites, analysis of genotype
better characterize parental lines, improve the effectiveness × environment interaction provides opportunities to select
of crossing strategies, and track genes in segregating for stable genotypes. As outlined by Ortiz et al. (on CD,
progenies. Although still costly, marker-assisted selection JAS), international wheat improvement at CIMMYT has
(MAS) appears to be routinely used for a few traits by included shuttle breeding at two contrasting locations in
wheat breeding programs worldwide. The genetic potential Mexico to facilitate selection of genotypes with wide
of re-synthesized hexaploid germplasm (when crossed to adaptation and durable resistance to rust and Septoria,
elite cultivars) was investigated by Ogbonnaya et al. They while incorporating as wide a range of genetic diversity as
found that such synthetic-derived lines yielded 8-30% possible into the thousand or so new entries that are
higher than the best local check in multi-site trials across distributed in international nurseries annually. Their article
diverse regions of Australia. Their results reinforce points out that CIMMYT’s primary generic target product
previous research conducted at CIMMYT that found that has been “genetically enhanced seed-embedded
lines derived from synthetic wheat have the potential to technology” which considers both strategic germplasm
significantly improve grain yield across environments. enhancement and adaptive breeding to mega-environments.
Kishii et al. (p. 120, these proceedings) reiterate the idea It discusses whether CIMMYT and similar CGIAR centers
that a great number of useful genes in ancestral wheat will in the future invest more resources in strategic
species could be transferred into wheat, based on previous germplasm enhancement, while adaptive breeding would be
CIMMYT efforts using wild relatives, including Ae. conducted progressively more by national agricultural
tauschii, T. monococcum, T. dicoccoides, and T. timopheevi. research systems (NARSs). (Strategic germplasm
However, Brennan and Martin’s article “Returns to enhancement would include identification and utilization of
investment in new breeding technologies” (on CD, novel genetic variation, e.g. from landraces and wild
Euphytica) advocates that breeding programs should species––including production of re-synthesized wheat.)
carefully assess the likely economic returns from the value Given the mission of IARCs within the international
of incorporating new approaches into their programs, a development assistance community, if their products are to
decision that is likely to be based on the scale of the change significantly, they must consider the needs and
breeding operation, with low cost investments being more relative strength of NARSs on a case by case basis.
universally accessible.

The article by Trethowan and Crossa (on CD, Euphytica) in participatory varietal selection, thereby extending the
analyzed 40 years of international spring bread wheat trials. potential impact of international public goods germplasm.
The analysis confirmed the relevance of shuttle breeding Advances in wheat improvement must also consider
between two locations in Mexico for global wheat wheat’s final end-uses. Negative correlations between grain
improvement, since selection environments generated in yield, grain protein concentration, and final end-use are
Mexico associate well with global target areas. They described by De Pauw and his colleagues in the article
describe how integrating information from international “Shifting undesirable correlations” (on CD, Euphytica).
sites with that obtained in Mexico helps to improve the They concluded that the undesirable correlations of grain
efficiency of CIMMYT’s global wheat breeding effort. For yield, grain protein concentration, and time to maturity can
more than 40 years, cooperating breeders from many be shifted by developing plants, which efficiently produce
countries have grown these trials, provided their elite and partition carbohydrates to grain yield and have
germplasm, and returned data to CIMMYT, which has improved nitrogen- and water-use efficiency. Improvements
made the compiled results available to all cooperators. in these traits could also be transferred to wheat cultivars in
Ammar et al. (p. 108, these proceedings) also highlighted water- and nitrogen-deficient areas. They showed that
the successes of the international durum wheat yield trial simultaneous selection for quantitative and quality traits
over the last 22 years, based both on the shuttle-breeding with the inclusion of marker-assisted selection, can shift
approach and the global network of NARS cooperators for these undesirable correlations. Echoing previous statements
information feedback. Without this unprecedented global on the value of wild species, Peña (p. 172, these
cooperation, none of the impacts (for example, in proceedings) remarks that introducing protein-enhancing
improving yield under favorable and marginal genes from Triticum dicoccoides is a strategy to increase
environments and enhancing disease resistance) would have grain protein content while simultaneously tackling the
been possible. inherent problem of improving both grain yield and grain
The articles by Chapman et al. and Ortiz-Ferrara et al.
(on CD, Euphytica) assess the advantages of using a global Addressing a subject worthy of a symposium in its own
approach by incorporating key genes (e.g., for plant height) right, Duveiller and coauthors (on CD, Euphytica) present
in wheat breeding lines and emphasizing regional efforts strategies aimed at minimizing or controlling yield losses
through participatory research and client-oriented plant from major diseases and pests relevant to intensive irrigated
breeding, respectively. In the article “Relationships between wheat systems in the developing world. Options suggested
height and yield in near-isogenic spring wheats that contrast include integrated crop management practices; breeding for
for major reduced height genes” Chapman and co-authors genetic resistance; rotations; minimizing physiological
showed how the environment influenced the phenotypic stresses and consequent susceptibility by timely sowing and
effects of two major dwarfing genes (Rht1 and Rht2). Their adequate use of fertilizers; and fungicide application. In
results confirm the advantage of incorporating such genes their article “The challenges of maintaining wheat
in wheat cultivars, since there was a ca. 10% yield gain for productivity: pests, diseases, and potential epidemics,” they
lines possessing such genes, which was more evident in also advise about the risk of changes in disease spectra as a
trials where the mean height of semidwarf isolines result of climate changes and demonstrate the complex
exceeded about 80 cm. Genotype-by-environment relationships among crop physiology, disease resistance,
interaction, especially of the cross-over type, was identified and yield.
by participants at the symposium as a major concern,
impeding improvement especially of quantitative traits. Regional Challenges
Eagles et al. (p. 103, these proceedings) suggested that
Several papers addressed wheat improvement in major
molecular and statistical technologies can be used to assist
grain baskets around the world: Joshi and co-workers (on
breeding for polygenic traits such as yield. Large data sets
CD, Euphytica) point out that India “faces a critical
of the type generated by plant breeding programs are
challenge in maintaining food security in the face of its
necessary, along with a large-scale genotyping of national
growing population.” Indian wheat breeders should
and international entries via available markers.
therefore aim to improve the crop to address heat stress
Ortiz-Ferrara et al., in their article “Partnering with farmers (exacerbated by global warming due to climate change);
to accelerate adoption of new technologies in South Asia to water scarcity due dwindling water supplies for irrigation;
improve wheat productivity,” describe how several farmer- the growing threat of new virulence in diseases such as
preferred technologies have been identified for adverse wheat rusts and leaf blight; continuous adoption of zero-till
conditions in eastern India and Nepal. Due to this and other resource conservation technologies, particularly
participatory-research approach, grain harvests by resource- in the intensive and highly productive rice-wheat systems;
poor farmers significantly increased (15-70%) in locations and a high demand for better quality wheat. Challenges to
where farmers, scientists, extension specialists, non- wheat production in South Asia in terms of biotic and
governmental organizations, and the private sector engaged abiotic stresses are also described by Chatrath et al (on

CD, Euphytica). They point to stagnating wheat yields and To gain an overview of the constraints that breeders are
the declining productivity of wheat-rice systems due to facing, a survey was conducted covering 19 countries,
intensive tillage and burning of residues, which lead to the representing 90% of all wheat grown and produced in less
depletion of soil organic carbon. Excessive nutrient mining, developed countries (Kosina et al., on CD, Euphytica). The
imbalanced fertilization and over-exploitation of water most significant constraints to wheat production were
resources are the other factors responsible for declining reported to be heat and water stress, weeds, and diseases.
productivity. Addition of organic matter to soil through Access to mechanization and credit availability were the
green manuring and crop residue recycling, balanced socioeconomic constraints most often highlighted. Lack of
fertilization, integrated nutrient management, and crop resources for field station operations is an important
diversification is suggested to improve total productivity in infrastructural constraint. The most desired outputs from
the region (see also Gupta and Sayre [on CD, JAS] for partnerships with international agricultural centers include
their analysis of the benefits of conservation agriculture in germplasm development and exchange, assistance in
the region). capacity building, and knowledge sharing.

Identification of wheat genotypes with high and stable grain Progress in Understanding the Physiological Basis of
yield is of particular relevance for poor farmers. Sharma et Yield
al. (on CD, Euphytica) report results for the Eastern
Gangetic Plains Yield Trials, grown in India, Nepal, and Two papers (Fischer; Foulkes et al., on CD, JAS) review
Bangladesh from 1999 to 2005. Lines with improved yield recent work on the physiological basis of genetic increases
stability and disease resistance were identified and released, in wheat yield potential, with the latter focusing more on
which underlines the importance and relevance of regional winter wheat. Data from the last 10 years in northwestern
wheat breeding programs. Similarly, Zhou et al. (on CD, Mexico indicate that yield potential progress in CIMMYT
Euphytica) evaluated genetic gains for grain yield in two spring wheat has slowed to around 0.50% per year although
regions of the Southern China Winter Wheat area, using physiological understanding has advanced. New research
leading cultivars released from 1949 to 2000. Results reinforces the importance of spike dry weight (g/m2) at
showed average annual genetic gain of about 0.31% and anthesis in yield determination, and lengthening the spike
0.74%, respectively. In region 1, yield components did not growth period through manipulation of photoperiod
change, though plant height was reduced; in region 2 sensitivity looks promising, a subject which is addressed in
genetic improvement of grain yield was attributed to more depth in the paper by Miralles and Slafer (on CD,
increased thousand-kernel weight (0.65%, P
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