Response of two cycles of phenotypic mass selection and heritability on two tropical sweet corn (Zea mays L. Saccharata) populations

Two cycles of phenotypic mass selection for ear length were conducted on two sweet corn (Zea mays L. saccharata) populations. In both populations, viz. the Manis Madu derived (M) and the population derived from its cross with Hybrid SSC 240 (MS), the realized cumulative response to selection was generally much lower than the predicted response. In the M populations, the predicted response from individual cycles was higher in the second cycle (M C2) (21.52%) than it was in the first (M C1) (19.31%), while the cumulative predicted response in M C2 was 45.94%. In the MS populations, a similar trend was seen, where the predicted response from individual cycles was 23.61% in MS C2 compared to 16.79% in MS C1, while the cumulative predicted response was 43.21% in MS C2. The two populations responded differently to the two cycles of selection, where, in the Manis Madu derived population, average realized response was attained only in the first cycle of selection (4.08%), while negative average response was observed in the second (-0.65%). The opposite was observed in the cross population, as average realized responses were -0.69 and 2.08% in MS C1 and MS C2, respectively. The average cumulative realized response was higher in M C2 (3.40%) than it was in MS C2 (1.38%). In the populations generated from Manis Madu, high broad-sense heritability estimates were revealed by plant height (89.1%), kernel total soluble solids (TSS) (86.2%), ear height (67.9%) and number of kernels/row (55.0%). Moderate estimates were shown by ear length (42.3%), fresh ear yield (36.8%) and ear weight (31.5%). In the cross populations, the highest broad- sense heritability estimate was revealed by number of ears/ha (99.8%), while low to moderate estimates were given by ear length (39.0%), days to maturity (27.9%) and days to tussling (25.1%). In the improved populations, M C2 and MS C2, plant height revealed high positive correlations with most of the traits investigated. Positive correlations were also observed among ear traits. It was concluded that phenotypic mass selection was found efficient for improvement of the two sweet corn populations, but more cycles would be required for more pronounced results.