Investigation of combining ability and heterosis in sorghum [Sorghum bicolor (L) Moench] genotypes under moisture stress areas

The most important prerequisite in sorghum crop improvement is the identification of suitable parents that can combine well and produce superior hybrids. However, a narrow genetic base, lack of potential hybrids and lack of information on the genetic components are the most important limiting factors for sorghum yield improvement. Therefore, the experiment was conducted to estimate the combining abilities and heterosis for yield and agronomic traits. A total of 42 sorghum genotypes were evaluated using an alpha lattice experimental design with two replications at Mieso and Kobo during the cropping season of 2019. Combined analysis of variance revealed highly significant differences due to genotypes for days to flowering, plant height, days to maturity, effective productive tillers, panicle exersion, panicle length, panicle width, panicle yield, grain yield and thousand seed weight traits. Based on general combining ability analysis, inbred lines P-9505 and P-9534 were identified as the best general combiners for both days to flowering and plant height traits; whereas inbred lines P-9501 and B5 were identified as the best general combiners for stay green traits. The hybrid crosses P-9534 x Melkam, B6 x ICRS-14 and MARC3 x Melkam were identified as the best specific combiners for grain yield, while the hybrid TX-623 x ICRS-14 was the best specific combiner for days to flowering, days to maturity, panicle length, panicle width and thousand-seed weight. The estimates of general and specific combining ability revealed the preponderance of non-additive gene action since the ratio of general combining ability to specific combining ability was less than unity for all the traits under study except for plant height. The maximum grain yield was obtained from the hybrids P-9534 x Melkam (6.32 tha^-1), followed by the hybrids B6 x ICRS-14 (5.92 tha^-1), TX-623 x ICRS-14 (5.88 tha^-1), P9511 x Melkam (5.78 tha^-1) and P-850341 x ICRS-14 (5.57 tha^-1). Among the hybrids, B6 x ICRS-14 exhibited (112.41 %) yield advantage over the mid parents, hybrid TX-623 x ICRS-14 exhibited (68.71 %) yield advantage over the better parent, whereas P-9534 x Melkam exhibited (30.71 %) yield advantage over the standard check for grain yield. Finally, based on the mean yield performance, heterosis response and combining ability estimates for grain yield and its components, the hybrid crosses P-9534 x Melkam, B6 x ICRS-14, TX-623 x ICRS-14, MARC3 x Melkam, MARC3 x ICRS-14, P9511 x Melkam and P-850341xICRS-14 were found to be the most promising and potential hybrids that could be exploited commercially after critical evaluation for their superiority and yield stability across locations over the years.