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Meiotic associations in a Triticum
aestivum L. em. THELL. x Agropyron
distichum (THUNB.) BEAUV. hybrid
R. DE. V. PIENAAR
Dept. of Genetics, University of Stellenobsch, Stellenbosch,
south Africa
The first wheat-Agropyron hybrids were produced fifty
years ago by SANDO and TSITSIN. Since then many crosses
between the different wheat and Agropyron species
were made in various countries in order to produce perennial
wheat or to transfer the resistance to a number of pathogens
from the Agropyron species to wheat (ARMSTRONG &
MCLENNAN 1944 ; CAUDERON, 1966a; CAUDERON & SAIGNE,
1961; ELLIOT, 1957; KNOTT, 1961, 1964, 1968; KNOTT et
al. 1977; POPE & LOVE; 1952; RILEY & KIMBER,
1966; SCHMIDT et al. 1956; SCHULZ-SCHAEFFER, 1970 ;
TSITSIN, 1962 ; WIENHUES, 1968, 1973 ; a.o.). None of these
crosses included Agropyron distichum (THUNB.)
BEAUV.
A. distichum is indigenous to the Cape Province,
South Africa, where it grows just above the high tide level
along the southern and south western coast. As a
rhizomatous, semi-xerophytic perennial which is 50-80 cm
tall, it is a good binder of the saline sand along these
coasts. It flowers during November and produces large (15-20
cm) wheat-like ears with 12 to 18 spikelets, each of which
contains 8 to 12 florets. Its chromosome number is 2n=28
(PIENAAR, 1955).
All the initial wheat x A. distichum crosses failed,
but in November 1976, the first successful cross was made
with the hexaploid wheat cultivar Chinese Spring (PIENAAR
et al, 1977). More crosses with other hexaploid and
tetraploid wheats were therefore made. During 1977 some 2394
florets on 18 different hexaploid wheat entries, as well as
744 durum wheat florets on 5 cultivars were crossed with
A. distichum.
None of these latter crosses yielded any filled kernels.
Only two endospermless kernels were produced; one kernel was
set on the hexaploid bread wheat cultivar Inia 66, and the
other on the North Dakotan durum wheat line D6647 which was
recently released in South Africa as the cultivar Nordum.
Both these kernels contained an embryo (half normal size) at
18 days after pollination. The embryos were excised and
cultured on sterile Difco Orchid Agar in McCarthney bottles.
After the embryos had grown to the three leaf stage they
were transplanted to pots in a growth chamber.
Unfortunately, the D6647 x A. distichum hybrid died
shortly after transplantation, but the Inia 66 x A.
distichum hybrid grew vigorously and was cloned to
produce 13 plants. Ten of these were treated with colchicine
to induce chromosome doubling, and the other three were kept
for meiotic and fertility studies on the F1
hybrid.
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