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

was approved by KU and OOA in 1991 (Table 6).
13. Inbreds Ki31 to Ki44 were released in 1992 (Table 7). The latest open-pollinated
variety Suwan 5 (Kasetsart Synthetic 5) was released this year.
All these OPVs are good sources of germplasm for inbred extraction and hybrid production.
Materials and methods.
Many accessions of maize germplasm have been introduced to Thailand since the beginning of
the breeding program. These have been planted in breeding nurseries for selection. The superior
or promising materials have been used in crossing exotic and indigenous sources for different
purposes. Materials which exhibited good performance have been used to extract inbred lines for
the development of the hybrid corn program.
The breeding procedures used in development of varieties include mass selection, backcrossing,
81 selection, half-sib, full-sib, line improvement, top crossing using the latest cycle of
SUwan 1 and Suwan 3 as testers, and test crossing using promising inbred lines or hybrids as
testers (Chutkaew, 1989).
Evaluation of varieties was initially done at research stations. Promising materials have
then been sent for testing both at experiment stations and in farmers' fields at different
locations in corn growing areas. Testing of elite varieties, composites, synthetics, and hybrids
has been conducted at many locations. To obtain more reliable information, data have been
collected over years, seasons and locations (Chutkaew, 1986).
Results and discussion.
By using a number of good sources of germplasm, appropriate breeding methodologies, evaluation
of varieties and analysis of data collected over years, seasons and locations, high yielding
OPVs and hybrids, have been approved by the committee of KU and the DOA, as mentioned above.
1. Evaluation of baby corn. The promising Kasetsart Baby Corn Three-way Cross 3501 (KBTX
3501) was developed in 1987 from (Ki39 x Ki20) x Ki40. Final testing with 12 other varieties
carried out at five provinces (Titatarn et a7. 1992) revealed that KBTX 3501 gave the highest
yield of fresh dehusked standard baby corn at 167 kg/rai, 47% higher than the check SUwan 2 (8)C7
yielding 113.7 kg/rai (Tables 8 and 10). Other promising varieties were SUwan 3101 and NS1 with
146.5 kg/rai and 123.6 kg/rai, respectively. KBTX 3501 had the lowest downy mildew infection
(0.2%), followed by the check Suwan 2 (0.4%) (Table 9).
The average yield of fresh baby corn with husks, dehusked, and incidence of downy mildew
infection from tests in five provinces in 1991, are shown in Table 10 (Titatarn et a7., 1992).
KBTX 3501 gave the highest yield both with husk (1,072.2 kg/rai) and dehusked (167.0 kg/rai) and
had the lowest downy mildew infection (0.2%) (Table 10). Baby corn also yields useful byproducts,
i.e. green husks and stalk which may be ensiled or sold as fodder for cattle.
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