Mining wheat germplasm collections for yield enhancing traits

The material in genebanks includes valuable traditional varieties and landr aces, non-domesticated species, advanced and obsolete cultivars, breeding l ines and genetic stock. It is the wide variety of potentially useful geneti c diversity that makes collections valuable. While most of the yield increa ses to date have resulted from manipulation of a few major traits (such as height, photoperiodism, and vernalization), meeting future demand for incre ased yields will require exploitation of novel genetic resources. Many trai ts have been reported to have potential to enhance yield, and high expressi on of these can be found in germplasm collections. To boost yield in irriga ted situations, spike fertility must be improved simultaneously with photos ynthetic capacity. CIMMYT's Wheat Genetic Resources program has identified a source of multi-ovary florets, with up to 6 kernels per floret. Lines fro m landrace collections have been identified that have very high chlorophyll concentration, which may increase leaf photosynthetic rate. High chlorophy ll concentration and high stomatal conductance are associated with heat tol erance. Recent studies, through augmented use of seed multiplication nurser ies, identified high expression of these traits in bank accessions, and bot h traits were heritable. Searches are underway for drought tolerance traits related to remobilization of stem fructans, awn photosynthesis, osmotic ad justment, and pubescence. Genetic diversity from wild relatives through the production of synthetic wheats has produced novel genetic diversity.