Regeneration of Russian wildrye foundation seed and its effect on genetic diversity and linkage disequilibrium

Authors: Mott, Ivan; Jensen, Kevin; Larson, Steven

Submitted to: Seed Technology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2012
Publication Date: 7/16/2012
Citation: Mott, I.W., Jensen, K.B., Larson, S.R. 2012. Regeneration of Russian wildrye foundation seed and its effect on genetic diversity and linkage disequilibrium. Seed Technol J. 34:79-86.

Interpretive Summary: The ability to maintain the genetic integrity of released cultivars is central to the restriction of seed generations, particularly in cross pollinating grasses where genes form groups that provide for increased agronomic performance. These groups are broken up if the plant material is carried for multiple generations through seed increase, thus losing the improved performance found in the new cultivars. The question that remains unanswered is what happens to these gene groups with additional generations often required for seed production. One such example is found in Russian wildrye where seed being produced is four generations past the original. Molecular genetic analysis has demonstrated that over four generations there is a 10% loss in these gene groups; however, that loss is not significant. Thus in Russian wildrye, up to four generations of seed production can be produced without significant changes in genetic structure and loss of functional gene groups that could potentially lead to detrimental changes in agronomic performance.

Technical Abstract: Maintaining the genetic integrity and performance of released cultivars over multiple generations of seed increase continues to be of concern in cross-pollinating grasses. It is not an uncommon practice when seed supplies are low or foundation seed is not available to designate registered seed as foundation seed (re-foundation), which adds one or more certified generations to the cultivar. One such example was in Russian wildrye (Psathyrostachys junceus (Fisch.) Nevski), which is a cross-pollinating, cool-season, bunchgrass native to steppe and semi-desert regions of Eurasia. AFLP analysis was used to test the effect of additional generations on the molecular genetic diversity and linkage disequilibrium within and among original foundation seed (1986), re-foundationed seed from registered seed (1992), and certified seed (2002) of the cultivar 'Bozoisky-Select' along with cultivars 'Vinall' and 'Mankota'. Average similarity coefficients within generations fell from 0.6031 in original foundation seed to 0.5920 in certified seed four generations later while the average similarity coefficient between generations fell from 0.6031 to 0.5826, respectively. Neighbor-joining phylogram based on total number of polymorphisms and PCA analysis grouped individuals of Vinall and Mankota into their respective groups, and grouped all Bozoisky-Select individuals into one, indivisible group. Linkage disequilibrium (LD) trended toward a loss of LD over generations of seed production, but the differences were not significant. Although there were slight decreases in genetic similarity over four generations of seed production, the changes were not enough to cause subdivisions of Bozoisky-Select seed using PCA or phylogenetic analysis and the breeder designation of new foundation seed from registered seed in 1992 did not significantly decrease LD in 2002 certified Bozoisky-Select seed.