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

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Varieties were obtained from Maize Program of Rockefeller Foundation.
Imported varieties outyielded recommended hybrids by 15-2~. COllaboration
among corn researchers in Asia increased with the development of the
Inter Asian COrn Program; breeding programs were reoriented towards development
of improved OPV's.
Technologies became available to increase corn production in farmers'
fields; Intensified COrn Production Program was laid out.
Downy mildew diseases built up. Intensified breeding to develop downy
mildew resistant (DMR) varieties.
Identify germplasm sources and procedures for increasing gene frequency for
DMR.
Maize hybridization program between native DMR and exotic germp1asm.
Philippine Government approved and funded OM research with provision of
extended training and production. This was centered at CMU, and MIT (now
USM).
Population improvement with multiple breeding objectives and utilization of
DMR germp1asm.
Private hybrid seed companies became active in hybrid maize business; from
the official institutions, inbred line development and maintenance was done
only at IPB-UPLB.
Extensive hybrid research program started at different government breeding
institutions.
Philippine Seedboard released the first hybrid from the IPB-uPLB for commercial
production.
Several private seed companies (local and international) became interested
in developing maize hybrids in the Philippines.
Breeding strategy and objectives
Hybrid maize R&D is pursued simultaneously with the development of synthetics through
standard inbreeding and combining ability evaluation techniques. A strong population improvement
program which supports the development of OPVs is also a source for inbred line development. At
USM, both yellow and white high combining lines are being received from CIMMYT. Before these
materials are entered into the diallel hybridization process, they are first evaluated for
adaptability in small plots and likewise, for purposes of seed increase. In the work on synthetics,
agronomically desirable S2s from DMR populations are crossed in all possible combinations
limiting the number of families to groups of 6, 8 or 10. The syn 0 or F1 generation is SUbjected
to random mating in isolation to produce the Syn 2 variety. Subsequent selections made from this
material allows for the maintenance and the improvement of the variety. Whenever possible,
inbreeding is carried up to S3 after which the line is maintained through mass sibbing.
The major objectives of hybrid maize research are relatively similar to those formulated
in the development of OPVs. Currently, the breeding objectives in the government sector are
geared towards the following:
1. Development of single crosses and modified single cross hybrids.
2. Development of inbreds from temperate and tropical crosses.
3. Development of inbreds and hybrids resistant/tolerant to biotic and abiotic stresses
with emphasis on downy mildew, stalk rot, drought, and acid soils.
4. Development of early maturing hybrids with flinty kernels.
5. Use of molecular markers such as-RFLP's and RAPD's for inbred conversion and line
identification.
6. Exploration of other germplasm sources especially those from international institutions
developing inbred lines for national programs such as CIMMYT and others.
Development of 51 and 52 lines from DMR maize populations
In collaboration with CIMMYT-Asian Regional Maize Program (ARMP) based in Thailand, USM
has been conducting extensive screening for maize resistance to the Philippine downy mildew,
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