Interspecific hybrids between Paspalum plicatulum and P. oteroi: a key tool for forage breeding

Abstract

Grama-tio-pedro (Paspalum oteroi Swallen) is a rare stoloniferous grass of the Plicatula group of Paspalum, well adapted to continuous grazing in areas subject to seasonal flooding in the Pantanal region, in central western Brazil. The species is a facultative apomictic (asexual reproduction by seed) tetraploid, sporadically cultivated on Pantanal farms, propagated either by cuttings or seed. Due to its potential for extensive cultivation and forage quality, Grama-tiopedro appears as a candidate for genetic improvement within the Plicatula group through plant breeding. We used a colchicine-induced sexual autotetraploid genotype of P. plicatulum Michx.to obtain interspecific hybrids using the apomictic species, P. oteroi, as pollen donor. The very similar meiotic chromosome behavior observed in both parents, with main quadrivalent and bivalent associations, suggested that P. oteroi is a natural autotetraploid. The hybrids showed less irregular meiotic behavior with fewer quadrivalents and more bivalents than either parent. Fertility among interspecific hybrids varied from complete sterility in some of them to seed productions in others that were approximately twice as much as for either parent. The great variability of seed set performance may well be a drastic genetic consequence of joining two homologous chromosome sets of P. plicatulum together with two homologous sets of P. oteroi that, in turn, have some homeology between them. Most hybrids reproduce by sexual means, thus, they could be used as female parents in backcrosses and in crosses with other species of the Plicatula group for interspecific gene transferring in breeding programs.

Mode of reproduction and meiotic chromosome behavior in Acroceras macrum

“…Acroceras macrum has a hermaphrodite floret and a male one growing together in its spikelets (Zuloaga et al, 1987), and an adequate experimental approach to evaluate its mating system should be considered. The relation between both pollination systems, autogamy and allogamy, should be obtained with the adequate management of the emasculation or no emasculation and isolation of inflorescences to promote selfing or outcrossing (Dart & Eckert, 2013;Gutiérrez, Medan, & Pensiero, 2006;Novo, Montenegro Valls, Galdeano, Honfi, & Espinoza, 2016).…”

Forage characters of different Paspalum species in Rio Grande do Sul: a meta-analysis

“…Grasses of the genus Paspalum are the most important forage plants used in pastures in South America (NOVO et al, 2015). In particular, Rio Grande do Sul has soil and climate conditions that enable species of the genus Paspalum to adapt well ecologically, resulting in increased forage production.…”

Cytological abnormalities and pollen abortion in interspecific hybrids ofNicotiana

“…The anther locule is where the pollen grain develops, and the developing anther consists of 17 microsporocytes in the center, surrounded by the tapetum and the anther wall [6,7]. The anther wall of 18 Nicotiana belongs to the basic type and is composed of the endothecium, two middle layers and the 19 tapetum [8,9].…”

“…Pollen development in most of the species includes the following key 3 1 stages: meiosis, tetrad and primexine development, microspore release, sporopollenin deposition, mitosis, 2 accumulation of starch or lipids, addition of pollenkitt or tryphine to the exine, and dehydration of the 3 cytoplasm [12][13][14]. Before the tetrad stage, the microsporocyte is encased in the callose wall, which is 4 synthesized by the meiocyte and deposited between the plasmalemma and the original cellulosic wall 5 during prophase I of meiosis [7,15]. This callose layer is vital for preventing cell cohesion and fusion 6 and useful as a template for the formation of species-specific exine-sculpting patterns; then, upon its 7 dissolution, the free microspores were released [7,[16][17][18][19][20].…”

“…Before the tetrad stage, the microsporocyte is encased in the callose wall, which is 4 synthesized by the meiocyte and deposited between the plasmalemma and the original cellulosic wall 5 during prophase I of meiosis [7,15]. This callose layer is vital for preventing cell cohesion and fusion 6 and useful as a template for the formation of species-specific exine-sculpting patterns; then, upon its 7 dissolution, the free microspores were released [7,[16][17][18][19][20].…”