Mining wheat germplasm collections for yield enhancing traits

The material in genebanks includes valuable traditional varieties andlandraces, non-domesticated species, advanced and obsolete cultivars,breeding lines and genetic stock. It is the wide variety of potentially usefulgenetic diversity that makes collections valuable. While most of the yieldincreases to date have resulted from manipulation of a few major traits(such as height, photoperiodism, and vernalization), meeting future demandfor increased yields will require exploitation of novel genetic resources.Many traits have been reported to have potential to enhance yield, andhigh expression of these can be found in germplasm collections. To boostyield in irrigated situations, spike fertility must be improved simultaneouslywith photosynthetic capacity. CIMMYT's Wheat Genetic Resourcesprogram has identified a source of multi-ovary florets, with up to 6 kernelsper floret. Lines from landrace collections have been identified that havevery high chlorophyll concentration, which may increase leaf photosyntheticrate. High chlorophyll concentration and high stomatal conductance areassociated with heat tolerance. Recent studies, through augmented use ofseed multiplication nurseries, identified high expression of these traits inbank accessions, and both traits were heritable. Searches are underway fordrought tolerance traits related to remobilization of stem fructans, awnphotosynthesis, osmotic adjustment, and pubescence. Genetic diversityfrom wild relatives through the production of synthetic wheats hasproduced novel genetic diversity.