Combining ability and heterotic pattern of waxy corn inbred lines (Zea mays L.)

With increasing demand for corn the apparent need is to improve productivity admist limited planting area. This study was conducted to determine the combining ability, heterosis, and identity outstanding waxy corn inbreds and crosses in terms of yield and other agronomic characters. Seven waxy corn inbred were evaluated using the diallel design proposed by Griffing (1956). Highly significant differences among entries for yield and ear height and significant in days to tassel, days to silk, and plant height was found. Results of general and specific combining ability analysis showed highly significant variation in GCA estimates for yield, starch content, plant and ear height and significant in days to tassel. For yield, the three inbreds that showed positives values were those developed from Macapuno, Lagkit and Lagkitan. The cross Lagkitan x PG6 obtained the highest and the only significant SCA for yield. Based on principal component analysis, the inbreds can be separated in four groups: Group 1: PG6; Group 2: Lagkit and PG18; Group 3: Lagkitan and PG8; Group 4: Calumbaya and Macapuno. Crossing the varieties that belong to the same heterotic group results to a poor yield performance, while crossing inbreds located to a different heterotic group results to high yield. Based on general combining ability Lagkitan would be a good parent as it combines well with the other inbreds. The cross Lagkitan x PG6 is anticipated to be the best performing cross as it has the highest midparent heterosis and high values for SCA for both yield and starch content. Lagkit and Lagkitan is another potentially good yielding cross. Inbreds that obtained high GCA estimates can undergo intra-population improvement while interpolation improvement program like reciprocal recurrent half-site selection can be used for the parents of high yielding crosses to produce improved hybrids.