A rise of ploidy level induces the expression of apomixis in Paspalum notatum

The common races of bahiagrass, Paspalum notatum, are tetraploid (2n=4x=40) and reproduce by aposporous apomixis. Paspalum notatum var. saurae is the corresponding diploid (2n=2x=20) sexual race that outbreeds due to self-inc ompatibility. Chromosome doubling was induced by colchicine treatments in t hree individual plants from a natural diploid population. Embryological stu dies demonstrated that one of the induced autotetraploid plants reproduced sexually. The other two autotetraploids were facultative apomicts. These re sults indicate that an unexpressed gene(s) for apomixis exists at the diplo id level. The expression of the trait is ploidy-dependent. The ploidy depen dency may act either on the locus controlling apomixis through some transcr iption factors or via a secondary locus which requires a higher allele dosa ge to affect the expression of the main locus.