Combining ability of low phytic acid (lpa1-1) and quality protein maize (QPM) lines for seed germination and vigour under stress and non-stress conditions

Abstract

Grain yield is more likely to be compromised by poor seed germination and vigour in low phytic acid (LPA) and quality protein maize (QPM) than normal maize (Nm), especially when grown under stressful tropical environmental conditions. The objectives of this study were to determine the effect of stress conditions on seed germination and vigour traits (percentage germination, seedling dry weight, average root and shoot length and vigour index) and to determine the GCA effects of the parental lines and SCA effects of the crosses. A ten parent half diallel (LPA, Nm, QPM lines) was subjected to the standard germination (non-stress) and accelerated aging (AA) (stress) tests. All seed lots were at the same physiological age and produced under the same season and conditions. Genotypic and group differences were investigated. General combining ability (GCA) and specific combining ability (SCA) effects were significant (P ≤ 0.001) for all traits under both stress and non-stress conditions indicating that both additive and non-additive gene effects were significant. Generally SCA effects were superior for all traits. The LPA lines displayed 61 % reduction in germination and 23–52 % reduction in vigour under stress conditions thereby underscoring challenges that are expected in deploying LPA maize in stress conditions. However, LPA line CM 31 exhibited large positive and mostly significant GCA effects, while two LPA × LPA crosses showed significant positive SCA effects. Results indicate breeding is required to improve both germination and vigour of the LPA lines to adapt them to tropical conditions that are generally stress-prone.