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Rebetzke G.J.,CSIRO | Bonnett D.G.,CSIRO | Reynolds M.P.,CIMMYT Int.
Journal of Experimental Botany | Year: 2016

Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned-awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38-7.93 t ha-1) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned-awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (-5%) and increased frequency (+0.8%) of small, shrivelled grains ('screenings') to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced screenings. © 2016 The Author 2016. Source


Bouffier B.,Limagrain Europe | Derory J.,Limagrain Europe | Murigneux A.,Limagrain Europe | Reynolds M.,CIMMYT Int. | Le Gouis J.,University Blaise Pascal
Agronomy Journal | Year: 2015

Wheat (Triticum aestivum L.) is the most widely cultivated crop worldwide and faces a wide range of stresses. To make effective crop improvement decisions, environmental characterization is of paramount importance. Th is study presents a new methodology for characterizing the environment that enables replacing the conventional arbitrary classification of the environment by a series of environmental covariates that capture and describe the stresses the plant encounters. Th ree CIMMYT bread wheat populations, combining complementary heat and drought adaptive traits, were grown over 3 yr in northwestern Mexico under limited irrigation, heat stress, and irrigated conditions. the network comprised 15 trials representing seven treatment × year combinations as experimental environments, referred to here as the “Environment”. Environmental characterization was performed at the trial scale. Twelve stress thresholds related to eight environmental factors were combined to obtain 11 potential growth limiting factors. Th irty-three environmental covariates were obtained by calculating when these limiting factors occurred for each of three key-developmental-phases across all trials. Cluster analysis allowed grouping environmental covariates into six distinct clusters corresponding to six “environmental scenarios”. One representative environmental covariate was extracted from each cluster and taken together explained more than 90% of the variance for yield in the Environment. Principal component analysis discriminated the seven experimental environments and identified its stress characteristics. We conclude that the method developed characterized the main stresses and their impact on average population performance, and the representative covariates efficiently replaced the Environment. As such, they will facilitate the dissection of genotype × environment interaction (GEI) for yield-related traits. © 2015 by the American Society of Agronomy. Source


Witt S.,Max Planck Institute of Molecular Plant Physiology | Galicia L.,CIMMYT | Lisec J.,Max Planck Institute of Molecular Plant Physiology | Cairns J.,CIMMYT Int. | And 4 more authors.
Molecular Plant | Year: 2012

Adaptation to abiotic stresses like drought is an important acquirement of agriculturally relevant crops like maize. Development of enhanced drought tolerance in crops grown in climatic zones where drought is a very dominant stress factor therefore plays an essential role in plant breeding. Previous studies demonstrated that corn yield potential and enhanced stress tolerance are associated traits. In this study, we analyzed six different maize hybrids for their ability to deal with drought stress in a greenhouse experiment. We were able to combine data from morphophysiological parameters measured under well-watered conditions and under water restriction with metabolic data from different organs. These different organs possessed distinct metabolite compositions, with the leaf blade displaying the most considerable metabolome changes following water deficiency. Whilst we could show a general increase in metabolite levels under drought stress, including changes in amino acids, sugars, sugar alcohols, and intermediates of the TCA cycle, these changes were not differential between maize hybrids that had previously been designated based on field trial data as either drought-tolerant or susceptible. The fact that data described here resulted from a greenhouse experiment with rather different growth conditions compared to natural ones in the field may explain why tolerance groups could not be confirmed in this study. We were, however, able to highlight several metabolites that displayed conserved responses to drought as well as metabolites whose levels correlated well with certain physiological traits. © 2011 The Author Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS. Source


Pask A.,CIMMYT Int. | Joshi A.K.,CIMMYT South Asia Regional Office | Manes Y.,CIMMYT Int. | Sharma I.,Directorate of Wheat Research | And 16 more authors.
Field Crops Research | Year: 2015

South Asia, which is already home to more than one-fifth of the world's population and rapidly growing, will require wheat yields to rise annually by 2.0-2.5% to meet demand and maintain food security. To address these challenges, a wheat phenotyping network was established in the region in 2009 to support national breeding programs by applying practical phenotyping techniques to increase selection success using a cooperative multi-location testing network. A number of trials have been grown to introduce new genetic diversity for stress adaptive traits, to establish their genetic bases, and to test a new generation of lines developed using physiological approaches. The 17th Semi-Arid Wheat Yield Trial (SAWYT), consisting of a group of 50 elite spring bread wheat advanced lines, bred in Mexico using both conventional (CON) and physiological trait (PT) approaches, was grown for two seasons 2009/10 and 2010/11. Data showed that PT lines gave superior yields overall, associated with higher grain weight, and with cooler vegetative and grain-filling canopy temperatures (CT); the CT trait is considered indicative of increased gas exchange, a likely consequence in these environments of superior vascular capacity including deeper rooting to access subsoil water. Local check genotypes, which were generally well adapted to the stressed environments tended to be 3-5 days earlier to heading than CIMMYT cultivars. Results demonstrate the potential to integrate physiological breeding approaches into genetic improvement for the region, particularly as future wheat production will take place under increasing water scarcity. © 2014 Elsevier B.V. Source

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