Alternative evolutionary pathways in Paspalum involving allotetraploidy, sexuality, and varied mating systems.

SCHEDLER MARA; REUTEMANN ANNA VERENA; HOJSGAARD DIEGO HERNÁN; ZILLI ALEX LEONEL; BRUGNOLI ELSA ANDREA; GALDEANO FLORENCIA; ACUÑA CARLOS ALBERTO; HONFI ANA I.; MARTINEZ ERIC JAVIER

Genes

MDPI

Año: 2023 vol. 14

Paspalum L. is a genus of mainly American grasses with many species and great genetic diversity. Most Paspalum species are agamic complexes with sexual diploids and apomictic polyploids. Polyploidy and apomixis are frequent in the Paspalum genus. A significant number of Paspalum polyploid species are sexual and differ in their genetic system. Some of these species have been analyzed by chromosome number and reproduction mode analysis from single individual plant collections. There are no population studies on the genetic and reproductive behaviour of these species. This work aimed to evaluate the cytogeographical distribution patterns, reproductive behaviour, pollination methods and seed fertility levels of several natural populations of four polyploid Paspalum species with two different genetic systems. A total of twenty populations from Paspalum durifolium, P. ionanthum, P. regnellii and P. urvillei were collected in north-eastern Argentina. Ploidy levels were analyzed by flow cytometry and checked through chromosome countings. The reproductive behaviour was determined at two stages of the reproductive cycle, ovules and seeds. At the ovule stage, by observation of mature embryo sacs and, at the seed stage, by flow cytometry seed screening. Seed set levels under self- and open-pollination conditions allowed to know the pollination syndrome and seed fertility. All populations of the four Paspalum species were tetraploid and sexual. Some individuals of P. durifolium and P. ionanthum showed a low proportion of aposporous embryo sacs, but the sexual pathway was the only observed at the seed stage. Populations of P. durifolium and P ionanthum had very low seed set level under self-pollination but they were fertile under open-pollination conditions, which indicates self-sterility and a high degree of allogamy within populations. All populations of P. regnellii and P. urvillei showed no evidence of apomixis either in the ovule or in the seed stage. Both species behaved as self-fertile with similar? seed set production for both self- and open-pollination conditions. This study represents the first population analysis on cytogeography, reproductive behaviour and seed fertility of sexual polyploid Paspalum species with two different genetic systems. Further genetic diversity analysis will be useful to characterize the genetic variability in each one of these species and the role that polyploidy and sexuality had in the origin and evolution of these species.