Sweet corn and baby corn improvement project of Kasetsart University

In Thailand, sweet corn and baby corn are among the most popular and economically important vegetables. Their export values are annually more than 1,000 million bahts. The objectives of the KU Sweet Corn and Baby Corn Improvement Project are 1) to develop sweet corn inbreds for producing high-yielding hybrids with good eating quality for the fresh market and processing and 2) to develop baby corn inbreds for producing male-sterile single crosses for used in non-detasseled baby corn production. Exotic sweet corn varieties with the shrunken-2 (sh2), brittle-1 (bt 1), and sugary 1 (su 1) genes were introduced and crossed with elite field corn inbreds and varieties of Kasetsart University. Populations were developed and improved by 3-4 cycles of recurrent selection for better adaptation and agronomic traits. Then lines were extracted from selected populations and developed by pedigree selection. These lines were evaluated using line x tester analysis at S3-S4 crossed with inbred testers, followed their heterotic patterns. Furthermore, a diallel cross was employed for evaluation of the combining ability of the inbreds and their hybrids. The 1st and 2nd years of testing of these hybrids for yield and quality (sweetness and tenderness) were conducted at the National Corn and Sorghum Research Center. The 3rd year hybrids were evaluated in the cooperative trial at various locations. An elite inbred yield trial and hybrid seed production were also tested. The best hybrids were selected for release to farmers and processing plants in the 4th year. In addition, the most elite inbreds were improved for better traits by using back crossing. Breeding for non-detasseled baby corn varieties utilized cytoplasmic male sterility (CMS) type C from IITA, Nigeria and Guatemala backcrossed into the Suwan 2 variety, giving Kasetsart 1. Male-sterile inbreds were developed by backcrossing Kasetsart 1 variety, with promising baby corn inbreds. The BC4-BC5 lines were used for making male sterile (no detasseling required) baby corn single crosses. The results of research and development efforts were INSEE 1, a sweet corn single cross with sh2 gene, and Kasetsart 1, a male sterile baby corn variety. They were released to farmers and processing plants in 1995.