Native Grasses for Biomass Production at High Elevations - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 107

patterns. However, the high growing point of basin wildrye is susceptible to
clipping and grazing [ 23 , 55 , 56 ], and it is difficult to establish good stands due
to poor seedling vigor [ 21 ]. The release of Continental basin wildrye demonstrates
that there is sufficient genetic variation within the species to improve seedling
establishment [ 50 ]. Moreover, interspecific hybridization is being used to introgress
rhizome genes into basin wildrye [ 10 ], which is expected to improve its grazing
tolerance. Basin wildrye is susceptible to black grass bugs, including Irbisia
pacifica and Labops hesperius , which can decimate grass monocultures [ 57 ].
Poor seed fill, low germination, and weak seedling vigor are the major limita-
tions of basin wildrye [ 21 ]. Although the relatively large spikes of basin wildrye can
produce thousands of seeds, these seeds readily disarticulate from the spikelet
rachilla [ 7 ] and are prone to seed shattering [ 58 ]. Basin wildrye seed production
fields require close scrutiny to prevent seed losses and ensure complete physiolog-
ical development of the caryopsis [ 23 , 58 ]. Moreover, the timing of seed harvest
may be complicated by the fact that individual plants are genetically variable and
may show variation in the timing of flowering and seed development [ 10 , 58 ]. Thus,
it has been speculated that seed performance problems associated with basin
wildrye may be partly attributed to the temptation to harvest seed before it is
physiologically mature [ 58 ].
The potential of creeping wildrye as a forage or biomass crop is derived from its
adaptation to moist saline-alkaline soils [ 34 , 59 ]. The cultivar Rio produced
between 10,000 and 13,800 kg ha 1 in fields with soil salinities of 12.9-21.0
dS/m EC e [ 34 ]. Although creeping wildrye is a relatively poor seed producer and
has dormant recalcitrant seeds and weak seedling vigor, this species is not prone to
seed shattering [ 14 , 58 , 59 ]. Once established, the aggressive rhizomes of creeping
wildrye rapidly spread to produce better coverage, provide exceptional resiliency to
clipping and mowing, and typically survive for many years [ 14 ]. However, this
species may lack the biomass accumulation potential of taller statured species such
as tall wheatgrass or basin wildrye [ 48 , 60 ]. Moreover, seed and forage production
typically declines when stands are left to become sod bound.
Hybrids between creeping and basin wildryes are partially fertile, and it has been
suggested that it may be possible to introgress simply inherited traits from one
species to another [ 43 ]. In particular, Dewey [ 43 ] suggested that the seed germina-
tion of creeping wildrye could be improved by introgression of genes from basin
wildrye and the growth habit of caespitose basin wildrye could be improved by
introgression of rhizome genes from creeping wildrye. Likewise, Larson and
Kellogg [ 58 ] suggested that introgression of a recessive gene variant that abolishes
seed abscission from creeping to basin wildrye could be used to improve ripening
and development of basin wildrye seeds. Moreover, the F 1 hybrids of creeping
wildrye and basin wildrye hybrids display increased plant biomass, with up to
14,100 kg ha 1 observed with no irrigation or fertilizer in Cache Co., UT. The
creeping and basin wildrye parents of this hybrid produced 4,600 and 9,600 kg ha 1
in the same experiment. Progeny of these hybrids display transgressive segregation
for biomass, forage quality, and many other traits including rhizomes and seed
retention [ 10 , 60 , 61 ]. These observations suggest possibilities of improving the