Genetic transfer from several apomictic tetraploid Paspalum species to an elite group of sexual plants

Abstract

Basic findings from classical genetic studies are available for exploiting apomixis in the breeding of several forage grass genera. Most Paspalum species are multiploid with a sexual diploid cytotype and conspecific apomictic polyploid (mainly tetraploid) cytotypes. Experimental tetraploidized diploids reproduce sexually and, when crossed with natural apomictic tetraploids, yield hybrid populations that segregate for reproductive mode. Genetic studies indicated that apomixis is inherited as a monogenic dominant factor. We recombined 50 selected sexual hybrids obtained from crosses between a tetraploidized sexual genotype of P. plicatulum and 9 natural apomictic tetraploid accessions of 6 species of the Plicatula group. A synthetic sexual tetraploid population (SSTP) of 600 individuals from mixed seed of the 50 intercrossed hybrids was space‐planted in the field. Based on evaluations of plant vigor, seed set, ergot tolerance, regrowth after flowering, and cold tolerance, 31 plants were selected. Crosses between most selected plants and two testers, which belonged to P. guenoarum, were performed, and the generated progeny was planted into the field following a randomized block design with 3 replications. The progeny test was evaluated for seed fertility, biomass yield, and cold tolerance. This procedure allowed selection of 10 elite plants from the SSTP. These plants should contain genes recombined from six apomictic species, without the genetic determinants for apomixis. They may be polycrossed to generate an improved sexual population, or crossed with other apomictic genotypes to obtain improved apomictic hybrids.

How to Become an Apomixis Model: The Multifaceted Case of Paspalum

“…Although this approach can result much more complicated than cytoembryological analyses and progeny tests, it is expected to provide a good estimation of apomixis capacity and can be extended to high numbers of individuals. Finally, the lack of available apomixis-linked markers in many Paspalum species, including the Plicatula group, makes the use of cytometric seed analysis an attractive screening technique for determining the reproductive mode [ 138 ].…”

“…This procedure allowed the transfer of the genetic diversity present among geographically and genetically distant ecotypes into a single sexual and cross-pollinated population [ 68 , 139 ]. More recently, a similar approach has been used to create a sexual tetraploid population in the Plicatula group [ 138 ]. In this case, nine accessions from six species with contrasting morphological characteristics were crossed to a single sexual induced genotype.…”

“…Although RSCA was expected to be more appropriate for exploiting heterosis since it was developed to accumulate heterotic effects over cycles, no difference was observed between the RPS and RSCA procedures for increasing forage yield [ 141 ]. A modified version of RSCA was used to identify superior tetraploid hybrids within the sexual population of Plicatula [ 138 ]. In this case, an initial phase of phenotypic selection was used to reduce the number of superior sexual hybrids, which were test-crossed to two elite apomictic clones belonging to P. guenoarum .…”

Environmental influence on reproductive traits of buffel grass facultative apomictic genotypes and its implication in plant breeding

“…Therefore, although most of the progeny are formed asexually and have a maternal genotype, the capacity to form seeds via sexual reproduction is also retained. Consequently, as reported by Novo et al (2020), controlled crosses between facultative apomicts and obligate apomicts (used as female and male parents, respectively) could allow new and desirable genetic combinations. For hybridization purposes, facultative apomictic genetic resources should gather desirable agronomic traits, high sexual expression, and cross-fertility (Acuña et al, 2007).…”

Reproduction mode and apospory expressivity of selected hybrids of Paspalum notatum Flgge

“…The selected genotypes, with superior agronomic characteristics fixed by apomictic reproduction at the tetraploid level in the breeding programs can be considered potential new cultivars (Acuña et al, 2009;Acuña et al, 2011;Jank et al, 2014;Zilli et al, 2015;Novo et al, 2020).…”