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

Peronosc lerospora phi 1ippinensis Weston. S1 and S2 famil ies derived from four DMR pool s consisting
of tropical early and late white/yellow materials are being screened separately under
Thailand and Philippine conditions. According to the data available, Philippine screened
materials show remarkably higher natural OM resistance than the same materials screened in
Thailand. Percent OM infection at USM ranges from 0 to 100. Those families which show a high
level of DMR with superior agronomic attributes are being used in the formation of synthetics and
OPVs and/or bulked as progenitors for the development of experimental varieties. The following
USM developed and released OPVs are originally CIMMYT-ARMP germplasm based. USM Var 1 (Pop. 78­
DMR), USM Var 2 (Sta. Rosa 8073), USM Var 3 (Pop. 28-DMR), USM Var 4 (Pop. 75-DMR) and USM Var 10
(Pop. 72). In the same way, the released materials from DA-DVIARC are derived from CIMMYT
populations. These varieties are categorized as "semi-synthetics" since they were developed from
balanced-bulks of seeds from ears harvested from agronomically superior plants within selected
families.
With regards to the maximum potential of hybrids, results of maximum yield research
studies on maize conducted by Pamplona et al. (1988) at USMARC, showed that hybrids differed
significantly in their response to varying rates of fertilizer, population densities, and
irrigation. Using P3228 and YCH 55, the lowest yield of 10.36 t/ha was obtained in plants
fertilized with 150-60-60 kg NPK. Yield was further increased to 10.79 and 10.67 t/ha when
fertilizer was increased to 250-150-150 and 500-300-300 kg NPK/ha, respectively. Likewise,
increasing population density from 70,000 to 90,000 plants/ha increased yield from 8.46% to 11.30
t/ha. Irrigated plants produced 10.88 t/ha, which was 0.55 t/ha higher than non-irrigated
plants. No significant interaction effects were observed in any of the different treatment
combinations involVing the four variables.
In a related development, outstanding farmers using hybrids attained yield records ranging
from 7.3 to 13.00 t/ha under actual farm circumstances, similar to those obtained at experiment
stations.
Variety testing and release
Under Philippine regulations, a maize cultivar is released for commercial grain production
if it has passed a series of agronomic performance tests. The last of these is the multilocation
National Cooperative Test (NCT) conducted for at least two seasons in 12 experiment stations
strategically located throughout the country. On the basis of the results, the Corn and Sorghum
Technical Working Group (CSTWG) recommends the outstanding varieties to the Philippine Seed Board
for approval. On-farm data, if available, are considered to complement data from the experiment
stations.
Between 1982 and 1992, about 30 hybrid maize cultivars were released for commercial
production against 12 OPVs approved. A majority of the released hybrids had yellow-flint
endosperm. Half of the OPVs were either yellow or white with flinty endosperm. Some OPVs showed
comparable yields with the hybrids and their maturity was within the desired range. The most
recent maize varieties/hybrids released from 1990 to 1992 are presented in Table 4.
Management and handling of developed materials
Most hybrid seed companies operating in the Philippines have their own marketing branch so
that they can directly sell their products. The Philippine Government acknowledges the active
participation of the private sector not only in the development of high yielding hybrids but also
in the promotion and adoption of their hybrids, through their extension efforts and demonstration
trials.
In the government sector, where lack of capabilities hinders the promotion and widescale
production and distribution of seeds, coupled with inefficient processing facilities to handle
large volumes of seed, developed hybrids and inbreds would become a public variety since everybody
has access to the parental materials at a cost and with due acknowledgement of the breeding
institution. Likewise, for seed producers, especially the established and capable agricultural
cooperatives who wish to venture into hybrid seed production, they could have access to the
parental seed at the breeding institution on a per hectare basis.
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