Fertility and Reproductive Pathways In Diploid and Triploid Miscanthus Sinensis

Miscanthus sinensis is a popular ornamental grass and has additional potential as a bioenergy crop.  In some regards, the ability of M. sinensis to withstand a broad range of climatic and cultural conditions is desirable, but its propensity to rapidly colonize open and disturbed environments has allowed it to naturalize and become weedy in some regions in the U.S.  Considering the value of this crop, the development and documentation of infertile forms would be desirable. Triploid plants were evaluated for male (pollen viability staining) and female (seed set and germination) fertility.  Pollen viability staining, seed set, and germination of seeds from triploid plants was reduced 19, 73, and 39%, respectively compared to the controls.  Overall, relative female fertility of individual triploids clones {(% seed set × % germination for triploid)/(% seed set × % germination for diploid control)} was reduced substantially and ranged from 49% to 0.7%. Additionally, we examined the reproductive pathways of triploid plants by evaluating the 2C genome sizes of progeny derived from open pollinations.  The limited progeny arising from open pollinated triploids were predominantly aneuploids with 2C genome sizes intermediate between diploids and triploids.  There was no clear evidence of apomixis, selfing, or triploid × triploid fertilization events observed among triploid parents.  Formation of unreduced gametes was infrequent for both ploidy levels (~1.4%).   The considerable reduction in female fertility in some triploid clones combined with the limited production of primarily aneuploid progeny, provides highly infertile alternatives to existing diploid cultivars.