Current limitations on phenotyping EW restrict the integration of this secondary trait into wheat breeding pipelines. In this study we evaluated the application of high-resolution spectral information as a proxy estimate of the trait and developed an efficient indirect method for the selection of genotypes with high EW density.
The Elite Spring Wheat Yield Trial (ESWYT) is a replicated yield trial that contains spring bread wheat (Triticum aestivum) germplasm adapted to Mega-environment 1 (ME1) which represents the optimally irrigated, low rainfall areas. Major stresses include leaf, stem and yellow rusts, Karnal bunt, and lodging. Representative areas include the Gangetic Valley (India), the Indus Valley (Pakistan), the Nile Valley (Egypt), irrigated river valleys in parts of China (e.g. Chengdu), and the Yaqui Valley (Mexico). This ME encompasses 36 million hectares spread primarily over Asia and Africa between 350S -350N latitudes. White (amber)-grained types are preferred by consumers of wheat in the vast majority of the areas. It is distributed to upto 200 locations and contains 50 entries.
The Harvest Plus Yield Trial (HPYT) contains spring bread wheat (Triticum aestivum) germplasm adapted to ME1 (Optimally Irrigated, low rainfall environment) and ME5 (Warmer area environment) environments. It has total 50 entries with 2 replications, white grain color and distributed to more than 70 locations.
CIMMYT annually distributes improved germplasm developed by its researchers and partners in international nurseries trials and experiments. The High Temperature Wheat Yield Trial (HTWYT) is a replicated yield trial that contains spring bread wheat (Triticum aestivum) germplasm adapted to Mega-environment 1 (ME1) which represents high temperature areas.
The Semi-Arid Wheat Yield Trial (SAWYT) is a replicated yield trial that contains spring bread wheat (Triticum aestivum) germplasm adapted to low rainfall, drought prone environments typically receiving less than 500 mm of water available during the cropping cycle. The combination of water-use efficiency and water responsive broad adaptation plus yield potential is important in drought environments where rainfall is frequently erratic across and within years. Stripe rust, leaf rust and stem rust, root rots, nematodes, and bunts are the key biotic constraints. Typical target environments include winter rain or Mediterranean-type drought associated with post-flowering moisture stress and heat stress such as those found at Aleppo (Syria), Settat (Morocco) and Marcos Juarez (Argentina), all classified by CIMMYT within Wheat Mega Environment 4 (Low rainfall, semi-arid environment; ME4: SA). It is distributed to 150 locations, and contains 50 entries.
Within the framework of SATYN, two types of nurseries are produced: SATYN series with odd numbers are lines for drought-stressed areas, and SATYN series with even numbers are lines for heat stress conditions. These nurseries have been phenotyped in the major wheat-growing mega environments through the International Wheat Improvement Network (IWIN) and the Cereal System Initiative for South Asia (CSISA) network, which included a total of 136 environments (site-year combinations) in major spring wheat-growing countries such as Bangladesh, China, Egypt, India, Iran, Mexico, Nepal, and Pakistan.
The data contained in these datasets can be used to implement Bayesian generalized kernel regression methods for genome-enabled prediction in the statistical software R, The accompanying paper describes the building process of 7 kernel methods (linear, polynomial, sigmoid, Gaussian and Arc-cosine 1, Arc-cosine L).
The Semi-Arid Wheat Screening Nursery (SAWSN) is a single replicate trial that contains diverse spring bread wheat (Triticum aestivum) germplasm adapted to low rainfall, drought prone, semi-arid environments typically receiving less than 500 mm of water available during the cropping cycle. CIMMYT's breeding approach attempts to combine high yield potential with drought resistance for ME4. The combination of water-use efficiency and water responsive traits plus yield potential is important in drought environments where rainfall is frequently erratic across years. When rains are significantly above average in certain years, the crop must respond appropriately (water responsive) with higher yields, while expressing resistance to the wider suite of diseases that appear under more favorable conditions. Constrains including leaf, stem and yellow rusts, and Septoria spp., Fusarium spp., Pyrenophora tritici-repentis tan spot, nematodes and root rots must be considered. It is distributed to 120 locations, and contains 150-250 entries.
The Stem Rust Resistance Screening Nursery is a single replicate nursery that contains diverse spring bread wheat (Triticum aestivum) germplasm adapted to all mega-environments with total 50-100 entries and white/red grain color.
The Helminthium Leaf Blight Screening Nursery is a single replicate nursery that contains diverse spring bread wheat (Triticum aestivum) germplasm with total 50-100 entries and 2 REPs.