Seed quality of reciprocal maize single crosses and their parental inbred lines

Abstract

Five direct and reciprocal early hybrids, five direct and reciprocal late hybrids and a total of their 12 parental inbred lines were used in order to test reciprocal effects among hybrids in early germination phase and seed quality of their parental inbred lines. Five hybrids were of early maturity FAO 300-400 group, and five of late maturity FAO 500-600 group. In the early group one line of Lancaster origin (L1) was in common, and in direct crosses used as male parent, while in reciprocal crosses as female parent. The same case was with late hybrids where another Lancaster line (L2) was in common. In 2015 and 2016 all the material was multiplied in hand pollination and after six months of storage three tests according to ISTA standards were performed: standard germination test (SGT), cold-test (CT) and vigor radicle test (RE). According to the Analysis of variance, a strong reciprocal effect was found among early hybrids for four out of five parameters in RE and SGT, while it was found only for RE in late hybrids. However, in CT none of the parameters had significant reciprocal effect. Two tested Lancaster inbreds were superior in the hybrids over non-Lancaster lines when used as maternal components, while as lines per se they did not display such superiority. Mid-parent heterosis (MPH) ranged from -62.32% to 211.11% in RE test, with an average of 44.26%; from -10.15% to 17.93% in SGT test, with an average of 6.27%, and from -5.31% to 4.49% in CT, with an average of 0.64%. Significant differences of MPH were found for nine pairs of reciprocal hybrids for RE, three pairs for SGT and seven pairs for CT. This shows that reciprocal differences in MPH were higher as the applied level of stress during early seed growth raised. All the results showed very complicated mode of inheritance of tested traits in the early developmental stages of young plants, including the phenomenon of heterosis which is expressed already at the germination stage.