World Journal of Agricultural Research, 2018, Vol. 6, No. 2, 37-48 Available online at http://pubs.sciepub.com/wjar/6/2/2 ©Science and Education Publishing DOI:10.12691/wjar-6-2-2 Estimation of General and Specific Combining Ability of Maize Inbred Lines Using Single Cross Testers for Earliness Benard Mbuvi 1,* , Murenga Mwimali 2 , Mwangi Githiri 1 1 Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi, Kenya 2 Kenya Agricultural and Livestock Research Organization (KALRO), Nairobi, Kenya *Corresponding author: benardmasila@gmail.com Abstract Maize (Zea mays L.) is third most consumed crop worldwide after rice and wheat. Maize is the main staple food in sub-Saharan Africa and Kenya, however, production has continuously been low over the past years. A line by tester analysis was carried out for 30 inbred lines and two testers to evaluate the GCA and SCA effects for yield and associated traits at three locations in Kenya during the 2016/2017 growing season. There were significant GCA and SCA mean squares indicating that both additive and non-additive gene effects contributed to the inheritance of the traits studied. Sum of squares of GCA was more than of SCA hence additive main effects contributed more to the inheritance of the traits than non-additive gene effects. Lines 1, 17, 6, 29 and 30 were good general combiners for grain yield. Testcrosses L30×T2 (4.40 t ha -1 ), L13×T1 (3.85 t ha -1 ), L20×T1 (3.59 t ha -1 ) and L9×T1 (3.52 t ha -1 ) yielded higher than best check mean and had good specific combining ability for grain yield and earliness in anthesis and silking dates. These genotypes can be evaluated further for grain yield and earliness and commercially released for use in areas with short rains. Keywords: general combining ability, specific combining ability, line by tester, single cross testers, earliness Cite This Article: Benard Mbuvi, Murenga Mwimali, and Mwangi Githiri, “Estimation of General and Specific Combining Ability of Maize Inbred Lines Using Single Cross Testers for Earliness.” World Journal of Agricultural Research, vol. 6, no. 2 (2018): 37-48. doi: 10.12691/wjar-6-2-2. 1. Introduction Maize (Zea mays L.) is ranked third most consumed cereal crop in the world for food, feed, and fodder after rice and wheat [1]. The average yield of maize worldwide between 2004 and 2014 was 5.11 t ha -1 with world largest producers, USA, China and Brazil contributing an average of 7.24 t ha -1 while sub-Saharan Africa contributing 1.58 t ha -1 to world average yield [2]. In sub-Saharan Africa and Kenya, maize is depended by small-scale farmers as a major source of food and income [3]. Although maize is a staple food in Kenya and sub-Saharan Africa, its demand is higher than its production thus affecting food security [4,5]. Causes of low production have been the use of poor seed, overdependence in poor and unpredictable rains, small-scale farming and occurrence of pests and diseases [6]. Therefore, there is urgent requirement to increase maize production in Kenya and sub-Saharan Africa by introducing more improved hybrids [5]. Introduction of maize hybrids has effectively increased maize acreage and yield in the recent past because of hybrid vigour [7]. Combining ability studies are key in developing improved maize hybrids in maize breeding [3]. Combining ability is the capability of an inbred line to combine well with other inbred lines to form elite hybrids; it is the relative capability of a genotype to transfer its good traits to its offspring [8]. Combining ability studies help plant breeders in the identification of inbred lines that are best combiners and give high yield without making all possible crosses among potential parents which is costly and wastes time [9]. Combining ability is categorized into general combining ability (GCA) and specific combining ability (SCA) [10]. General combining ability (GCA) is average line performance in hybrid combinations while specific combining ability (SCA) refers to when some hybrid combinations are better or worse than the average performance of the parents [8]. Combining ability studies give information on additive and non-additive gene action in the expression of heterosis, improving the efficiency of selection of good hybrids for improvement [3]. GCA gives information on additive gene effects while SCA gives information on non-additive gene effects [11] . Lines with good GCA have elite genes originating from either testers or lines crossed to form good hybrids while lines with good SCA originate from the interaction effect of crossing the lines and the testers [8]. In plant breeding programs, the line by tester mating design discovered by Kemphthorne (1957) is extensively used in combining ability studies giving information on the general combining ability (GCA) of lines, testers and specific combining ability (SCA) of crosses [12]. The mating design gives information on type and amount of gene action, heritability, effects of combining ability, amount and type of heterosis for different traits [13].