Native Grasses for Biomass Production at High Elevations - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 110

moist years on dryland cites [ 72 ]. Intermediate is less competitive with alfalfa
( Medicago sativa L.) than bromegrass or crested wheatgrass and maintains a more
desirable grass-alfalfa balance. Smart et al. [ 73 ] reported that May to June forage of
smooth bromegrass outyielded intermediate wheatgrass by 750 kg ha 1 during the
first harvest season, but only by 275 kg ha 1 at the second harvest season. Across
three locations in Nebraska, intermediate wheatgrass averaged 5,301 kg ha 1 and
ranged from 3,801 to 6,401 kg ha 1 [ 74 ]. At Mead, NE, between 1986 and 1987,
Manska intermediate wheatgrass averaged 7,201 kg ha 1 compared to 6,800 kg ha 1
for cultivars Oahe and Slate; however, by 1989, the overall biomass was twice that
with differences between cultivars reported [ 75 ]. Black and Reitz [ 76 ] reported that
with increased row spacing width from 76- to 152-cm biomass went from about
3,500 kg ha 1 to 3,100 kg ha 1 under fertilization (67 kg ha 1 N and 22 kg ha 1 P);
however, under no fertilization biomass production remained at around
2,000 kg ha 1 regardless of row spacing width. Dry matter yields averaged over
four test sites, and multiple years in North Dakota were 4,226, 4,228, and
4,509 kg ha 1 , respectively, for intermediate wheatgrass cultivars Manska, Oahe,
and Reliant [ 77 ]. Rush intermediate wheatgrass cultivar ranked among the four
highest entries for overall biomass yield across five irrigation levels, averaging
23,700 kg ha 1 , and was the single best entry at low-irrigation levels,
19,100 kg ha 1 , in a comparison of 21 warm-season and six cool-season grasses [ 1 ].
Intermediate wheatgrass has increased the productivity of marginal land where
bromegrass and orchard grass ( Dactylis glomerata L.) are not well adapted. Its
water requirement is between smooth bromegrass and crested wheatgrass, and it
flowers from 1 to 2 weeks later than these grasses. Because of its relatively late
maturity and quality retention after frost, intermediate wheatgrass has been effec-
tively used for grazing during the fall and early winter in the Intermountain Region.
Although intermediate wheatgrass is noted for its productivity, it is sensitive to
mismanagement or intense defoliation. Early cultivars failed to persist more than 4-
5 years and were not good seed producers, prompting many to prefer either smooth
bromegrass or crested wheatgrass. However, these problems have been overcome
through the development of improved cultivars [ 78 ]. The forage quality of inter-
mediate wheatgrass also declines at advanced stages of maturity. Intermediate
wheatgrass is sensitive to mismanagement at the time of harvesting in the shooting
stage [ 79 ].

Genetic Resources

Species in the genus Thinopyrum [ 35 ] have been of the greatest interest to wheat
breeders since the early 1930s when N. V. Tsitsin first demonstrated that
T. ponticum (Podp.) Barkworth and D. R. Dewey, intermediate wheatgrass, and
T. junceum (L.) ´ .L¨ve hybridized readily with various species of Triticum
[ 80 ]. Chromosome numbers in intermediate wheatgrass range from 2 n 42 to

52 with the aneuploids arising from unequal chromosome disjunction or unreduced

¼