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

Abstract

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-incompatibility. Chromosome doubling was induced by colchicine treatments in three individual plants from a natural diploid population. Embryological studies demonstrated that one of the induced autotetraploid plants reproduced sexually. The other two autotetraploids were facultative apomicts. These results indicate that an unexpressed gene(s) for apomixis exists at the diploid level. The expression of the trait is ploidydependent. The ploidy dependency may act either on the locus controlling apomixis through some transcription factors or via a secondary locus which requires a higher allele dosage to affect the expression of the main locus.

Determination of the mode of reproduction of bahiagrass hybrids using cytoembryological analysis and molecular markers

“…Valle and Savidan (1996) reported that the occurrence of two types of sacs in the same embryonic egg in apomictic plants of Brachiaria is considered indicative of facultative apomixis. Quarin et al (2001) also mentioned that an artificially induced tetraploid population may have apomictic, sexual, or facultative mode of reproduction, indicating that apomictic genes exist in diploid plants and that expression of these genes is repressed in the diploid level.…”

Chromosome doubling in Paspalum notatum var. saure (cultivar Pensacola)

“…The affected tissue is disorganized, resulting in irregularities in the chromosome number (Sybenga 1992), so some tissues or plants can have sectors with and sectors without chromosome doubling (Taylor and Quesenberry 1996). Quarin et al (2001) induced chromosome doubling in 24 diploid P. notatum seedlings, where tetraploidization was confirmed in only one plant while another had octaploid and tetraploid sectors. In the same study, P. notatum chromosomes were duplicated by colchicine application directly in the culture medium of plantlets.…”

Agronomic evaluation of Paspalum notatum Flügge under the influence of photoperiod

“…The work was performed in this breeding program. The reproduction mode of the sexual genitors was described by Quarin et al (2001) and the ploidy level of the other ecotypes was analyzed by Fachinetto et al (2012). Paspalum notatum 'Pensacola' and two native ecotypes of Rio Grande do Sul, denominated André da Rocha and Bagual, collected in the 1980s, were used as sources.…”