Genetic distance and the relationship with heterosis and reproductive behavior in tetraploid bahiagrass hybrids

Abstract

Bahiagrass (Paspalum notatum Flüggé) is one of the main components of the South American grasslands, and it is cultivated for forage and turf around the world. At present, hybridization is the most common breeding technique for the species, and its goal is to obtain superior apomictic hybrids. The objective of the present study was to determine the relationship between heterosis, reproductive behavior, and genetic distances between parents in tetraploid bahiagrass. Genetic distance between 24 sexual tetraploid genotypes and 24 apomictic tetraploid genotypes of P. notatum was evaluated using simple sequence repeat (SSR) and inter simple sequence repeat (ISSR) markers. Crosses were made between parents with low, intermediate, or high genetic distances. Six families were generated. A marker linked to apospory in bahiagrass was used to determine segregation for mode of reproduction, and embryo sacs were characterized to estimate the level of apospory expressivity. The ratio between sexual and aposporous hybrids ranged from 1:1 to 9:1 among families. Discontinuous variation for apospory expressivity was observed among hybrids, with either low or high levels being exhibited. A significant relationship between genetic distance and proportion of aposporous hybrids was observed. Heterosis was observed for all the evaluated traits and its level was dependent on the parental combination. Genetic distances between parents were related to heterosis, mainly for forage yield, which is the most important trait in forage species. Hence, molecular markers may be useful to predict the occurrence of heterosis for this trait.

Significant progressive heterobeltiosis in banana crossbreeding

“…In the present study, we observed a positive signi cant correlation between grandparent heterobeltiosis for bunch weight and genetic distance between NARITA parents. These results agree with those of Marcón et al [40] who also reported a positive relationship between genetic distances among parents and heterosis for forage yield in bahiagrass (Paspalum notatum). However, these results contradict with what was observed by Tenkouano et al [31] in triploid plantains and secondary triploid plantain-derived hybrids.…”

High-Resolution Linkage Map With Allele Dosage Allows the Identification of Regions Governing Complex Traits and Apospory in Guinea Grass (Megathyrsus maximus)

“…These species undergo asexual propagation by seeds (Nogler, 1984), which allows the fixation of hybrid vigor in apomictic individuals and their use in the creation of uniform pastures (Jank et al, 2011). Experimental field data showed that aposporous apomixis in tropical forage grasses follows 1:1 Mendelian segregation, indicating monogenic inheritance (Savidan, 1981;Valle et al, 1994;Chen et al, 2000;Savidan, 2000), although a recent study suggests that this reproductive mode should be treated as a quantitative trait (Marcón et al, 2019), and provide evidence of the uncoupling of apomixis in neo-apomictic species, such as guinea grass (Kaushal et al, 2008;Kaushal et al, 2019). Molecularly, the apospory-specific genomic region (ASGR), which is responsible for apospory, is highly conserved among apomictic species (Gualtieri et al, 2006).…”

Recurrent phenotypic selection and recurrent selection based on combining ability in tetraploid bahiagrass

“…Regarding the occurrence of heterosis in P. notatum , we have already demonstrated that crossing very distant parents favors increasing the level of heterosis for forage yield (Marcón et al., 2019). In this work, given that the SSTP and apomictic genotypes used as male parents have different origins, a high genetic distance could be expected between them.…”

“…The occurrence of heterosis in the progenies obtained by the two breeding techniques was evaluated following the methodology proposed by Marcón et al. (2019). This methodology allowed determination of the genetic effects associated with the expression of forage yield and the proportion of families exhibiting heterosis.…”