Combining ability of inbred lines of maize (zea mays l.) and stability of respective single crosses in Kiambu and Embu Counties Of Kenya.
Kariuki, Jeniffer Muthoni
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Despite the fact that virtually all households in Kenya grow maize over 60% of them are net maize buyers because they do not produce enough for their consumption. Kenya‘s current food supply situation and outlook give cause for serious concern. Maize is the main staple food averaging over 80% of total cereals (rice, wheat, millet and sorghum) in Kenya. Maize stocks are estimated to be depleted at all levels throughout the country. According to strategic grain bank report on food security, the National Grain Reserve had 2.2 million bags of the staple by the end of February 2012 instead of the required four million. Combining ability of inbred lines is important information in maize hybrid breeding programs incorporating materials from various germplasm sources. This study was conducted to select lines with good combining ability and to determine the stability of their respective single crosses in different environments. The trials were conducted in 2012 at experimental stations of Kenya Agricultural and Livestock Research Organization (KALRO) Muguga South and Embu in Kiambu and Embu counties of Kenya respectively. The study was conducted with 36 crosses. General combining ability (GCA) and specific combining ability (SCA) were determined for grain yield, height of the ear, plant height and disease scores using Griffing‘s method (1956). Interaction between the genotypes and environment was also determined among the crosses. Disease scores for natural infestation of grey leaf spot and maize streak virus disease were visually scored on scale of 1-5 with 1 being resistant and 5 susceptible by assessing the severity of the symptoms on the selected plants. The experiment was laid out in a 6 x 6 lattice complete randomized block design (RBCD) with two replications. Combining ability was estimated by method 1 model 1 of Griffing‘s (1956) which was used to partition the lattice adjusted treatment mean squares into GCA, SCA without reciprocal effects. The data was subjected to analysis of variance (ANOVA) using Genstat 12 program for individual test crosses as well as for combined environments considering environments as random effects and crosses as fixed effects. Mean separation was done using Tukey‘s comparison method at 0.05% significance level. Mean separation for MSV and grain yield in Muguga and for GLS in Embu was not done because the variance ratio for the crosses was not significant. The best combiners for grain yield were MUL 508 XMUL 516 (entry 9), POP A x MUL 541(entry 23) and MUL 513 X MUL 114 (entry 31) with entry 23 (POPAxMUL541) giving the highest yield of 8 t/ha. Data on grain yield showed no significant difference between the sites but there was significant difference on crosses grain yield. Grain yield showed positive significant correlation with ear height (r=0.4292) and plant height (r= 0.5830). Data on disease scores where natural infestation was visually scored showed majority of the crosses had a score of one confirming their near immunity status. The results will be useful to breeders and farmers in selecting the potential parental materials for improvement in maize breeding programs.