Unravelling the ambiguous reproductive biology of Paspalum malacophyllum: a decades old story clarified

Authors: HOJSGAARD, D - University Of Gottingen; Burson, Byron; QUARIN, C - National University Of Argentina; MARTINEZ, E - National University Of Argentina

Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2015
Publication Date: 7/1/2016
Citation: Hojsgaard, D.H., Burson, B.L., Quarin, C.L., Martinez, E.J. 2016. Unravelling the ambiguous reproductive biology of Paspalum malacophyllum: A decades old story clarified. Genetic Resources and Crop Evolution. 63:1063-1071.

Interpretive Summary: Ribbed paspalum (Paspalum malacophyllum) is a grass that is related to both bahiagrass and dallisgrass, and its natural area of distribution extends from Argentina to Mexico. The grass has good palatability and is readily eaten by cattle, but it does not persist under grazing. However, it is resistant to ergot, a disease that reduces seed set in dallisgrass and other grasses and is very toxic to cattle. Because it is resistant to ergot, ribbed paspalum is important because the genes for resistance can be transferred to other grasses by crossing them. Since the grasses (primarily dallisgrass and bahiagrass) that get ergot reproduce by a vegetative form of reproduction known as apomixis (seed set without fertilization), they can only be used as the pollen or male parent in a cross. Therefore, ribbed paspalum has to be used as the female parent in the cross, but before this is done, plant breeders have to know how this grass reproduces. Published reports on how the grass reproduces are contradictory and confusing. Some report the grass produces seed by normal sexual reproduction; others report it produces seed completely by vegetative means (apomixis); and others report plants of this grass produce seed by both methods but at different levels. Recent research using modern cytological and molecular tools have shown that most ribbed paspalum plants do produce seed by both sexual and apomictic reproduction and the frequency or level of each depends on the individual. This indicates that those plants that produce the highest frequency of seed by normal sexual reproduction can be used as the female parent in crosses with apomictic plants such as dallisgrass and bahiagrass. This information is extremely valuable to plant breeders attempting to improve these grasses because it increases the efficiency and productivity of the program.

Technical Abstract: A recent a manuscript was published by our group that analyzed the reproductive biology of the grass species Paspalum malacophyllum using traditional embryological techniques combined with current cytological and molecular methods. Our findings confirmed apparent contradictions regarding the reproductive behavior of P. malacophyllum from six independently published reports over the past six decades. Herein we summarize the main findings, conclusions, and validations of all previous studies, highlighting the need for using multiple approaches to characterize reproductive systems when using apomictic plants in a breeding program.