Inheritance of important traits in sweet corn single-cross hybrid

Sweet corn (Zea mays L. saccharata) is an important crop in Malaysia, and its production has continuously increased, mainly due to its high return. Single-cross Hybrid 969, an imported hybrid variety, has performed well and is widely planted throughout the country, proving it desirable as a source of inbred lines. Previous studies have generally indicated that complete dominance is important in the genetic control of yield traits in corn hybrids. Hence, many commercial single-cross hybrids which showed high inbreeding depression at early generations of inbreeding were found not suitable to be used as germplasm sources (Basra, 2002). Objectives of this study were to evaluate performance of the F1 and F2 populations of Hybrid 969, to determine inbreeding depression in the F2 population, to estimate broadsense heritability of the traits measured in the populations, and to predict gain from selection of the traits measured on the populations. Results show that the F2 population had all measurements significantly lower than the F1 population, except for days to tasseling and silking were the reverse was true. Estimates of inbreeding depression were highest for dehusked and husked fresh yield (-61.1% and -54.7%, respectively). This has resulted from increased homozygosity of the recessive alleles responsible for the control of these characters (as a result of selfing), the effects of which were masked or partly masked by dominant alleles in the heterozygous from in the F1 population. Days to tasseling was found to be the most heritable trait, followed by dehusked and husked ear diameter (91.0%, 81.5% and 74.4%, respectively). This indicates that these traits can be improved more rapidly through selection at early generations of segregation than those with lower heritability estimates (Bonos et al., 2003). Results also indicate that a substantial gain from selection of the top 20% of the population can be expected when phenotypic selection is used. In conclusion, significant differences in performance between the F1 and F2 populations indicate high inbreeding depression after one generation of selfing in the sweet corn Hybrid 969, although there were individuals in the F2 population that showed highly desirable performance. Hence, selection of these desirable segregants with the character of interest could be exploited for development of inbred lines derived from Hybrid 969.