Evaluation of different methods for assessing the reproductive mode of weeping lovegrass plants, Eragrostis curvula (Schrad.) Nees

Abstract

Weeping lovegrass is a forage grass cultivated in semiarid regions of the world that reproduces mainly by apomixis (diplospory), a process that involves the formation of asexual seeds and bypasses the processes of meiosis and fertilisation. The aim of this work was to evaluate and compare different techniques (cytoembryology, callose deposition, flow cytometry and progeny tests) to determine the reproductive mode of weeping lovegrass. Typical sexual and apomictic processes were clearly differentiated using cytoembryology, and different callose deposition patterns were observed in sexual and apomictic genotypes. Previous studies indicated that presence of callose on the cell wall of the megaspore mother cell is associated only with sexual processes. Nevertheless, our results also found callose deposition in apomictic genotypes, although clearly different from the pattern found in sexual processes, allowing discrimination between sexual and apomictic plants. Flow cytometry seed screening using individual seeds did not differentiate between sexual and apomictic plants as the embryo : endosperm DNA content ratio was similar in sexual and apomictic plants. Progeny tests using molecular markers showed uniform patterns in offspring from apomictic plants and variable patterns among the progeny of sexual plants. The results obtained from cytological studies and progeny tests were similar, indicating that both methods provide useful tools for determination of reproductive mode. However, the callose test with aniline blue was faster and easier to use than other techniques.

Mode of reproduction and meiotic chromosome behavior in Acroceras macrum

“…The observed of embryo sacs correspond to a Polygonum type, which has a typical structure of Paniceae (Anton & Cocucci, ), similar to the sexual sacs of Panicum elephantipes Nees (Urbani, ). Constitutions of these mature embryo sacs are almost indistinguishable from diplosporic unreduced ones by structural observation (Meier et al., ), but the wide extent of hybrids among progeny, as we found with the hybrid origin test on the four crosses in A. macrum , is attributable to a sexual origin of all of the 33 members of their progeny. Although a small fraction of the putative hybrids could not be demonstrated to have derived from the cross, the presence of a unique band, absent in both the mother and the putative father, is strong evidence that these putative nonhybrids did not result from an apomictic origin.…”

“…Diversity analysis by phenotypic or genotypic traits is one of the current support tools to study the reproduction mode of populations and through a proper design of cross progeny test. Molecular genetic markers are the most reliable for the study of segregation among progeny to infer the mode of reproduction (Acuña et al, 2005;Daurelio, Espinoza, Quarin, & Pessino, 2004;Schranz el al., 2006;Meier et al, 2011;Barrett, 2013;Garcia, Vigna, Sousa, Jungmann, & Cidade, 2013;Kozub et al, 2017). Adequate markers would be unlinked and monogenically inherited.…”

“…Among the Paniceae tribe, some of the apomictic pathways are detectable by microscopy methods by observing embryo sacs (Acuña, Martínez, & Quarin, ; Chapman & Busri, ; Kozub et al., ; Kumar, Chandra, Gupta, & Shukla, ; Naumova, Hayward, & Wagenvoort, ; Ortiz et al., ; Philipson, ; Quarin, ; Quarin & Burson, ; Quarin & Hanna, ; Warmke, ; Weiler et al., ). However, diplospory could be difficult to differentiate from sexual ones (Meier, Zappacosta, Selva, Pessino, & Echenique, ). Diversity analysis by phenotypic or genotypic traits is one of the current support tools to study the reproduction mode of populations and through a proper design of cross progeny test.…”

Increased apomixis expression concurrent with genetic and epigenetic variation in a newly synthesized Eragrostis curvula polyploid

“…These results indicated that in 2009 the plant continued to display a level of apomixis as high as that in 200713. Therefore, the rate of apomixis in colchiploid plant C shifted from near 0% in 2003 (21) to 85–90% in 2007 (16), and remained at similar values in 2009 (89,7%).…”

Repetitive sequences in Eragrostis curvula cDNA EST libraries obtained from genotypes with different ploidy

“…The most useful cultivars for forage are tetraploids (2n = 4x = 40) that reproduce by pseudogamous diplosporous apomixis (Crane 2001, Voigt et al 2004. In this asexual reproduction through seeds (Asker and Jerling 1992), the megasporocyte undergoes two rounds of mitotic division to form a non-reduced tetranucleate embryo sac with an egg, two synergids, and one polar nucleus (Meier et al 2011). Besides Eragrostis, diplosporous apomixis has been described in Agropyrum, Boechera, Paspalum, Poa, Tripsacum among other species (Nogler 1984, Barcaccia andAlbertini 2013).…”