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

were unacceptable in some parts due to yellow grain color. 4) F1 production was a tedious job
and farmers were not willing to purchase fresh seed every year at high cost.
More recently, some multinational seed companies, the local seed company, Rafhan Maize
Products Co. and Provincial Research Institutes are involved in the development and distribution
of hybrid maize seed. Hybrid seed is planted in a limited area (54,000-56,000 ha) by contract
growers in the Punjab Province in the spring season. All hybrid seed is provided by Rafhan Maize
Products Co. (Khan, 1993). During the main growing season (kharif) only 20 tons of hybrid seed
are provided by all multinational seed companies combined. The limited use of hybrid seed in
Pakistan is attributed to the following factors:
a. All exotic hybrids are of full-season maturity, about a month later than what farmer's
would prefer to grow.
b. Almost all hybrid seed is imported. This activity increases the price of hybrid seed
beyond the purchasing power of a common maize grower.
c. Imported hybrids are developed from full-season inbreds, which can not be successfully
produced in the subtropical environment of Pakistan. Parents of hybrids, therefore, can not be
maintained easily or grown without risk.
d. Most foreign hybrids are bred specifically for favorable growing conditions, but Pakistani
growers have experienced disappointments when these hybrids were grown under suboptimal conditions
or when stresses occurred during the growing season.
e. Because imported seed remains for a long time in shipment, its quality often deterio
rates.
f. Little incentives are provided by the Government to private seed companies.
For the above reasons, there is a need for short duration hybrids, well adapted to local
conditions, and whose seed could be cheaply and easily produced. Hybrids developed from elite
local populations could be the only suitable source of hybrid seed.
In the past, no serious attempts were made to locally develop and produce short duration
F1 hybrids for commercial cultivation. The hybrid breeding program could not be established on a
sound footing due to lack of financial resources and technical manpower, sound seed production
and distribution system, and many other related problems. Maize hybrids under relatively good
management can give higher yields than open-pollinated varieties with much better uniformity of
maturity, plant height, and disease resistance.
The hybrid maize breeding program was initiated with the following objectives:
1. To develop short duration F1 hybrids (85-90 days) for areas with intensive cropping
pattern and where late planting Virginia tobacco is grown.
2. To select high yielding and stable hybrids, resistant to leaf blights and stalk rots.
Development of inbred lines.
Research on inbred line development from four adapted and elite populations was started in
1984. With the availability of two seasons per year, selfing and selection was twice as fast as
having only one season per year. A standard pedigree selection proced~re was used where S2
plants were tested for general combining ability. Many S2 lines were discarded at this early
stage. Considerable work has been reported on the development of short duration maize hybrids by
numerous workers. Inoue and Okabe (1982) in a study on a method of breeding inbred lines of
maize reported visual selection to be very effective for vigor, ear morphology, disease, and
insect tolerance and lodging if inbred populations were derived from primary open-pollinated
varieties. Oyervides, et a7. (1985), reported that US Corn Belt populations could be a source of
useful alleles for yield, early maturity, and short plant height for tropical or sUbtropical
areas. Cross (1979) reported a new breeding technique for selecting early high yielding maize by
use of the marker gene Rnj (purple aleurone gene), which indicates the rate and/or duration of
grain filling.
On the basis of their combining ability from each group, selected inbred lines were
crossed to check their performance in hybrid combinations. Hybrids were tested in single cross,
three-way, and double cross combinations. Some good single cross hybrids were also crossed to
adapted improved open-pollinated varieties as double topcrosses. Selected hybrids were extensively
tested in multi location trials for several years.
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