Heterosis, Combining Ability and Yield Performance of Sorghum Hybrids for the Semi -Arid Lands of Kenya

Abstract

Sorghum is ranked third in importance in Kenya and forms an integral part in the farmers’ livelihoods as a food and nutritional security crop. Despite its critical role, its production and productivity has been low. Drought and use of low yielding unstable varieties are part of the major causes of the low production. A study was conducted at Kenya Agricultural and Livestock Research Organizations (KALRO) Kiboko and Kampi ya Mawe in 2014 and 2014-2015 with an aim of estimating the genetic potential, heterosis and grain yield stability of sorghum hybrids and their parents. A total of 34 male sterile lines from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) India and 12 restorer lines from ICRISAT Kenya were used to generate 34 F1 hybrids following the North Carolina Mating Design I. The hybrids and their parents were evaluated at the two sites in a 9 x 9 square lattice trial design in three replications. Data were collected on grain yield, fresh biomass yield and their related traits. The levels of heterosis, combining ability, correlation, heritability and stability were estimated. Highly significant genotypic differences were recorded for all the traits. Grain and biomass yield of the hybrids was largely determined by the per se performance of the parents. Five hybrids were better yielding than the checks ATX 623 x Macia and Seredo. Biomass and grain yield were significantly and positively correlated hence development of dual purpose hybrids is possible. Negative correlation between days to flowering and grain yield greatly demonstrated that early high yielding hybrids would escape drought hence fitting well in the production systems of the Semi-Arid lands (SALs). High phenotypic coefficients of variation (PCV) and genotypic coefficients of variation (GCV) scores for biomass yield, number of tillers and plant height shows that improvement is possible through selection. Selection would be more effective for fresh biomass yield, panicle exertion and plant height in hybrids and their parents due to high heritability. Heterosis was revealed with both positive and negative magnitude for the studied traits. Hybrids ICSA 11037 x Macia, ICSA 11004 x ICSR 24008 and ICSA 29007 x ICSR 24008 had high positive standard, mean and better parent heterosis for grain yield. Hence, these hybrids can be recommended for onfarm testing and possible release in Kenya. Inheritance of the traits was controlled by both additive and non- additive gene action hence genetic gains can be realized through direct selection. The best restorer for biomass yield improvement was ICSV 700 whereas ICSR 160 was a

good general combiner for grain yield. Wahi and Hakika were good combiners for shorter height. Yields of sorghum hybrids were greatly influenced by the genotype and the environment where they were cultivated. Hybrids ATX 623 x Macia, ICSA 11004 x ICSR 24008 and ICSA 11033 x ICSR 160 were high yielding and stable. Selection of hybrids could be done effectively using multiple environments data.