Influence of pollen dispersal and mating pattern in domestication of intermediate Wheatgrass, a novel perennial food crop

Intermediate wheatgrass (IWG) is a perennial forage grass that is
currently being domesticated as a grain crop. It is a primarily
wind-pollinated outcrossing species and expresses severe inbreeding
depression when self-pollinated. Characterization of pollen dispersal,
mating parameters, and change in genetic diversity due to pollen movement
is currently lacking in IWG. In this study, we examined pollen dispersal
in an IWG selection nursery by evaluating 846 progeny from 15 mother
plants and traced their parentage to 374 fathers. A set of 2500 genomic
loci was used to characterize the population. We assigned paternity to 769
(91%) progeny and the average number of fathers per mother plant was 37,
from an average of 56 progeny examined per mother. An extensive number
(80%) of pollination events occurred within 10 m of the mother plants.
Pollination success was not correlated with trait attributes of the
paternal genotypes. Mating system analysis confirmed that IWG is highly
out-crossing and inbreeding was virtually absent. Neither genetic
diversity nor the genome-estimated trait values of progeny were
significantly affected by pollinator distance. The distance of pollinator
in an IWG breeding nursery therefore was not found to be a major
contributor in maintaining genetic diversity. These findings reveal the
pollen dispersal model in IWG for the first time and its effect on genetic
diversity, which will be valuable in designing future IWG breeding
populations. Information generated and discussed in this study could be
applied in understanding gene flow and genetic diversity of other
open-pollinated species.