Seed dormancy of Paspalum sexual species from the Dilatata group (Poaceae)

ecological, physiological and genetic studies: Doctoral thesis abstract

Abstract

Paspalum dilatatum is a perennial warm-season grass whose incorporation into sown pastures is desired. However, like other non-domesticated species, it presents poor and irregular seedling emergence explained by seed dormancy. This characteristic is highly variable and genotype-dependent. Paspalum dilatatum cannot be bred because it is apomictic. Still, there are self-pollinated sexual species related to P. dilatatum, which can produce fertile hybrids that can be bred by conventional methods. To obtain an attractive cultigen, it is necessary to know the expression and heritability of seed dormancy in these species. In this work, ecological, physiological and genetic aspects of seed dormancy in sexual species of the Dilatata group were explored. First, field seedling emergence of different Paspalum species was modelled using environmental variables, and the results were associated with seed dormancy. It was evidenced that the emergence dynamics depend on the temperature and soil moisture. Contrary to expectation, high temperatures reduced the number of emerged seedlings due to a greater expression of seed dormancy. Second, the seed dormancy of the sexual species of the Dilatata group was quantified, and it was evaluated whether the differences between species can explain their geographic distributions. Paspalum urvillei has a larger distribution area, explained by a lower seed dormancy level. While the other species (P. dasypleurum, P. flavescens, P. plurinerve and P. vacarianum), with more restricted and allopatric distributions, showed higher dormancy levels associated with the rainfall level at each origin sites. Third, QTLs for seed dormancy were searched using a population of recombinant inbred lines between P. flavescens and P. plurinerve. The germination of the population was phenotyped, and the genetic map was obtained with genotyping-by-sequencing method. Four significant QTLs were found, revealing that seed dormancy in these species is explained by the additive effect of more than one locus.