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What is the Purpose in Dual-purpose Wheat Breeding? September, 1998 |
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By far grain monoculture is the predominant production system used for winter wheat throughout the world. Yet, Oklahoma wheat producers have successfully managed winter wheat not only for grain, but also as a cool-season forage resource. Recent survey data indicate that in some years more than 65% of the wheat acreage is planted for the intended dual-purpose of forage and grain production. Wheat variety development in the Great Plains traditionally has not differentiated between winter wheat intended for grain-only or dual-purpose production. As we learn more about growth of the wheat plant under early-planted conditions of a dual-purpose system, we have more reason to believe that a more targeted breeding strategy might produce varieties better adapted to that system. For example, consider that successful stand establishment depends upon elongation of the coleoptile to the soil surface. The coleoptile is a modified leaf which protects the first leaf during seedling emergence. Its length is affected by soil temperature. Hotter soil temperatures, as encountered in early September in Oklahoma, reduce coleoptile growth compared to October planting conditions. Coleoptile length is also genetically determined, which opens the door for selective breeding, but not without consideration to plant height. Most of the wheat varieties grown in Oklahoma are of the 'semidwarf' type, i.e., they contain a gene which reduces final plant height compared to the older standard-height varieties like Scout 66 and Triumph 64. Such varieties have one of two possible genes for semidwarfism; these are referred to as 'Rht1' or 'Rht2', an abbreviation for 'reduced height'. Unfortunately, the same gene that reduces final plant height also reduces the capacity of the coleoptile to elongate. One effective strategy, then, for developing
varieties tailor-made to dual-purpose production systems would be to select
for semidwarfing genes which reduce final plant height without reducing
coleoptile length. Fortunately, several semidwarfing genes are available, a
few of which appear to feature this genetic independence. Currently in our
breeding program, we are working with a semidwarfing gene from durum wheat and
another that resides in Australian spring wheat lines. Other selection
strategies may be used to develop varieties with improved adaptation to a
dual-purpose system. These will be discussed in future issues of
The Inside Scoop.
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