. Genetic variability, heritability, genetic advance and trait correlations in selected sorghum (Sorghum bicolor L. Moench) varieties

Study was carried out to estimate the genetic variability, heritability and genetic advance as well as association between yield and yield related traits in selected sorghum varieties. Ten sorghum varieties were evaluated in randomize complete block design with 2 replicates across two environments. Data were recorded on plant height, days to 50% flowering, number of productive tillers, panicle length, panicle width, panicle weight, 100 seed mass and grain yield. Mean squares were significant (P≤0.05) for all traits in the individual and combined analysis of variance, implying high variation in the sorghum population. Panicle length, panicle width, Dry panicle weight and 100 seed mass could be employed as target traits to improving grain yield. All the traits evaluated exhibited high genotypic and phenotypic components of variance than environmental variance, showing that characters in the population was genetically controlled and can be exploited in breeding programs. High heritability and estimated genetic advance as percentage of mean for most of the traits indicates the presence of additive genes and suggested reliable sorghum improvement through selection for the traits. Grain yield was significant and positively associated with days to 50% flowering, number of fertile tillers, panicle width, dry panicle weight and 100 seed mass. * Corresponding Author: Jimmy Morris Lado  Jim4wan@gmail.com International Journal of Agronomy and Agricultural Research (IJAAR) ISSN: 2223-7054 (Print) 2225-3610 (Online) http://www.innspub. net Vol. 11, No. 5, p. 47-56, 2017 Int. J. Agron. Agri. R. Jimmy et al. Page 48 Introduction Sorghum (Sorghum bicolor [L.] Moench) grain yields in Africa and Asia are generally low (0.95–1.17t/ha) compared to 3.63 t/ha reported in USA and Europe (FAOSTAT, 2011). The grain of sorghum is a major factor in the daily menu of millions of people while the stover is used to feed livestock (Devries et al., 2001). Being a native crop of Africa, tremendous number of variability exists in East Africa (MoARD, 2008). However, the existence of variation alone in the population is not adequate for improving suitable traits unless the genetic variability is well understood. The grain yield is an essential and complex trait and is a function of several component traits. In the mixed structure of a plant, most of the traits are interrelated. Direct selection on yield is not effective and it has been reported that it would be better if the structure of yield is examined through its components rather than directly to realize their mutual association (Grafius et al., 1964). Genetic improvement in sorghum yield depends on quality and magnitude of genetic variability, heritability and genetic advance in the population as well as the nature of association between yield and its components. This enables simultaneous selection for many traits associated with yield (Mahagan et al., 2011). Sorghum in general possesses a wide range of genetic variability (Sharma et al., 2006). Adequate variability provides options from which selections are made for improvement and possible hybridization. Binodh et al. (2008) reported that information on trait association in crops is essential for effective selection in crop improvement. The phenotype of a plant is the result of interaction of a large number of factors and final yield is the sum of effects of several component factors (Biradar et al., 1996). Correlation coefficients assist in deciding the direction of selection and number of traits to be looked at in improving grain yield. Heritability of a trait is important in determining its response to selection. Estimates of heritability assist breeders to allocate resources necessary to effectively select for desired traits and to achieve maximum genetic gain with little time and resources (Smalley et al., 2004). Estimates of heritability with genetic advance are more dependable and important than individual consideration of the parameters (Nwangburuk et al., 2012). When more traits are involved in correlation study, it becomes hard to determine the traits that really contribute to yield due to the existence of some amount of mutuality. The extent of variability is evaluated by GCV and PCV which provides information about relative amount of variation in different traits. According to Tah (2011) the extent of variability is measured by GCV and PCV which provide information about relative amount of variation in different traits studied. The present study was aimed to estimate the genetic variations, heritability and expected genetic advance in the selected sorghum varieties. Materials and methods Experimental locations The study was carried out during the 2015 short rain season at Kenyan Agricultural and Livestock Research Organization (KALRO) Kiboko and at the University of Nairobi Kabete Campus field stations. Kiboko station lies at altitude 960m above sea level with average annual rainfall of 548 mm and average minimum and maximum temperature of 16.6 and 29.40C respectively. The University of Nairobi, Kabete campus Field Station lies at an altitude of 1820 m above sea level with an average annual rainfall of 1000 mm and average maximum and minimum temperature of 23 and 160C respectively. The data for rainfall and temperature of the locations were obtained from their respective meteorological