Proceedings of the Fifth Asian Regional Maize Workshop - Search ...

Two synthetics, TH-2A and TH-2B, with average yields of 3-4 t/ha were released for
production in 1977 and 1978.
Composite VM-1, with a yield potential of 5-6 t/ha, was released for production in 1980
and since then has been highly appreciated by our farmers.
Since 1980, thanks to full cooperation with CI~, new possibilities opened up and since
then most of our maize varieties originated from CI~'s germp1asm. For instance, the first two
early maize varieties, MSB-49 and TSB-2, with yield potentials of 4-5 t/ha, were released for
production in 1983 and 1984. They have been the principal maize cu1tivars for areas using the
transplanting technique on wet land after two rice crops in North Vietn8lll. Later, 9 intermediate
and intermediate-late varieties with good adaptation to many ecological zones of Vietn8lll
with yield potentials of 4-6 t/ha were released from 1985 to 1991.
The OPI/s can be grouped as follows:
Early group: HLS, TSB-2, and CV-2, with yield potentials of 3-5 t/ha.
Early-intermediate group: MSB-49 , MSB-49B, HL-36 , and Gr-2, with yield potentials of 4-6 t/ha.
Intermediate and intermediate-late group: TSB-1, CV-1, VM-1, VN-1, and DT-6, with yield potentials
of 4-7 t/ha.
Good drought tolerant varieties: VM-1, VN-1, MSB-49 , MSB-49B, and CV-1.
Lodging resistant and saline-acid soil tolerant variety: MSB-49.
Downy mildew resistant variety: TSB-1, VN-1, Gr-2, CV-1, and CV-2.
The introduction of the improved OPI/s has increased the average yields in many areas where
intensive farming is practiced as well as in low input maize areas.
III.
The hybrid maize program (I+1P)
Since the 1970s, the I+1P has been costly and difficult to implement. A successful HMP
requires time, an adequate budget, and proper orientation.
In the 1960's, some hybrids and inbred lines from Rumania were introduced to Vietn8111 by
the Hanoi Agric. Univ. in cooperation with a Rumanian institution. After 2 years of testing,
this program failed even though under the supervision of Rumanian experts.
In 1972 and 1973, several hybrids and inbred lines were introduced from the Martonvasar
Inst., Hungary. This program was also unsuccessful and closed. The introduced hybrids and
inbred lines had severe adaptation problems in Vietnam:
Grown duration was too short, ~ less than in Europe.
He1minthosporium turcicum and H. maydis incidence was heavy, with a disease scale rating
of 8 or 9 (1 = healthy, 9 = highly susceptible)
All yield components were much reduced.
Therefore, their yield potential very low.
All the data obtained pointed to the conclusion that the European hybrids and inbred lines
adapted to temperate conditions were not adaptable to our tropical and humid conditions, and
could not be directly utilized in a breeding program in Vietnam.
Based on the above conclusions, since 1973 the National Maize Program of Vietnam, located
at its former headquarters in Song 80i Station, initiated two new activities: to create new
inbred1ines from tropical germplasm i.e. the improved populations; and to import tropical inbred
lines. Other international germplasm from different ecological zones had been only used as
donors of certain valuable characters.
At present, varietal and nonconventional hybrids have been also developed.
The I+1P is being strengthened to develop hybrids mostly to be planted in fertile soil
areas with highly intensive farming and irrigation, such as the delta of the Red river, the SE
area, the Mekong river, delta and the central plateau area.
In 1988, after 15 years of research, the NMRI had developed three single crosses ready for
testing. These were the early maturity hybrid LDSB-1, and the intermediates LDSB-2 and LDSB-3.
In 1991, the total initial area used for hybrid testing was about 500 ha. The test
including hybrids developed by NMRI, P-9901, and P-11 imported from Pacific seed Ltd., DK-888
introduced from CP-Thai1and, and Bioseed 9670 introduced from Bioseed Genetics-Vietnam Joint
Venture Ltd.
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