Combining ability for grain yield and silking of maize inbred lines derived from three open pollinated varieties released for mid altitudes of Rwanda: Comparison of Diallel and North Carolina Design II

Abstract

Maize (Zea mays L.) cropping systems have undergone extraordinary development in Rwanda during the past ten years, mainly due to the increase of agriculture productivity by the Crop Intensification Program (CIP). Consequently, there has been a shift from varieties from Open Pollinated Varieties (OPVs) to hybrid cultivars. The objective of this study was to estimate the general and specific combining abilities of inbred lines, developed from three OPVs released in mid-altitudes of Rwanda. Seventeen inbred lines were divided into female and male groups, and crossed using the North Carolina Design II (NCDII); while ten of them were crossed using Griffing’s Diallel Method 4 (GDM4). The resulting crosses were evaluated at Cyabayaga, Rubona and Bugarama in Rwanda from October 2015 to March 2016. Results showed that additive and non-additive effects controlled grain yield, but non-additive effects were predominant whereas additive and maternal effects predominantly controlled silking. Six inbred lines (RML0006, RML0014, RML0015, RML0018, RM0017 and RML0010) had high general combining abilities (GCAs) for grain yield and negligible GCAs for silking; whereas ten crosses had specific combining abilities (SCAs) superior to 1.5 t ha-1 for grain yield and negligible SCAs for silking. These six inbred lines will also be used to predict and form maize synthetic varieties; while the ten crosses with best SCAs will be utilised for the developing maize hybrid varieties with high yields and reduced silking time.

Key words: Additive effects, general combining ability, maternal effects, non-additive effects, specific combing ability