Microsporogenesis, viability and morphology of pollen grain in accessions of Cynodon L. C. Rich. (Poaceae)

Plants of the genus Cynodon were considered as weed for a long period. However, this scenario has changed when it was observed that many species could be used in forage farming and for the recovery of degraded areas. Due to the high expansive potential, Cynodon spp. became an option for producers and aroused interest for breeding programs, besides requiring further studies on genetic and cytogenetic variability. Research on meiosis in Cynodon are scarce since the inflorescences are small and the standardization of the stages of spikelet collections is difficult. The aim of the present study was to evaluate the microsporogenesis, viability and morphology of the pollen grains of two accessions of Cynodon dactylon var. dactylon (L.) Pers. (2n = 4x = 36, bermudagrass) and two accessions of Cynodon nlemfuensis var. nlemfuensis Vanderyst (2n = 2x = 18, stargrass). The slides were prepared by squash technique and stained with 2% carmine propionic. For the viability analyses of pollen grains, 2% propionic carmine and Alexander's stain were used. The measurements and the morphology of the pollen grains were defined from analyses with the acetolysis technique and scanning electron microscopy. The meiosis of the four accessions/species was regular. The staining tests showed variations in the viability rate of the pollen grain between the diploid and tetraploid species, being higher among the tetraploids. The pollen grains measured 21.1 and 28.8 μm on average for both species and were classified as oblate spheroidal, monocolpates and showed no ornamentation, such as spicules and other attachments with non-roughened, micro reticulated exine.