Abstract

This study aimed to improve the resistance to two major sweet corn diseases in Thailand: northern corn leaf blight (NCLB) and downy mildew (DM). Two sweet corn lines resistant to NCLB (PopHX75C1 and PopCH66C1) were crossed with two waxy corn inbred lines resistant to DM (F4305 and AGWX001) resulting in two hybrid groups: PopHX75C1 × F4305 (group X) and PopCH66C1 × AGWX001 (group C). Self-pollinated progenies from these groups were selected for resistance to both NCLB and DM and further self-pollinated to advanced generations. Disease resistance was evaluated under natural and artificial infection conditions. In the S6 generation, the 14 selected hybrids were assessed for ear yield and agronomic traits. Nine parental lines resisted both NCLB and DM, with the hybrid X3 × C6 demonstrating the highest ear yield of 14.67 tons ha−1. This hybrid also exhibited good eating quality and agronomic characteristics comparable to those of commercial varieties, with a 19% infection rate for NCLB and 7% for DM—lower than those of the commercial hybrids. These results indicate that the selected sweet corn lines with dual resistance to NCLB and DM have the potential as valuable parental lines for future breeding programs. These lines can be used to develop high-yield, disease-resistant hybrids, thereby improving the sustainability and productivity of sweet corn cultivation in Thailand.

Key words: sweet corn, northern corn leaf blight, downy mildew, line, hybrid, disease resistance