Heterosis estimation and heterotic grouping of sorghum [Sorghum bicolor (L) moench] inbred lines in dryland environments

Sorghum is one of the most vital cereal crops well adapted to the arid and semi-arid regions of Ethiopia. However, its productivity remains low compared to its potential, primarily due to severe and recurrent drought stress. To develop climate-resilient sorghum hybrids, it is essential to understand the extent of heterosis and identify heterotic groups comprising drought-tolerant inbred lines. Therefore, this study was conducted to quantify the magnitude of heterosis and to classify sorghum inbred lines into heterotic groups using specific combining ability (SCA) and general combining ability (GCA) across multiple traits. A total of 42 sorghum genotypes were evaluated using an alpha lattice design with two replications across two environments during the 2019 cropping season. Significant genetic differences among genotypes were observed for the traits studied across locations. Several top-performing and well-adapted hybrids P-9534 × Melkam (6.32 t ha -1 ), B6 × ICRS-14 (5.92 t ha -1 ), TX-623 × ICRS-14 (5.88 t ha -1 ), P9511 × Melkam (5.78 t ha -1 ), and P-850341 × ICRS-14 (5.57 t ha -1 ) were identified as promising for moisture-stressed environments. Among these, B6 × ICRS-14 exhibited the highest mid-parent heterosis (112.41%), TX-623 × ICRS-14 showed the highest better-parent heterosis (68.71%), and P-9534 × Melkam recorded the highest standard heterosis (30.71%) for grain yield. Heterotic grouping based on specific combining ability (SCA) classified the sorghum inbred lines into two distinct groups, while the general combining ability of multiple traits (HGCAMT) method identified three heterotic groups for the development of superior hybrid varieties. Combining ability-based heterotic grouping is a critical approach for identifying the most suitable parental lines for creating new, agronomically superior hybrids. Overall, several sorghum hybrids demonstrated superiority over their mid-parents, better-parents, and the standard check in terms of grain yield and key agronomic traits. Therefore, the hybrids P-9534 × Melkam, B6 × ICRS-14, TX-623 × ICRS-14, MARC3 × Melkam, MARC3 × ICRS-14, P-9511 × Melkam, and P-850341 × ICRS-14 were identified as superior performers with the potential to significantly increase sorghum productivity per unit area.