Genetic gain of maize (Zea mays L.) varieties in Ethiopia over 42 years (1973 - 2015)

Currently under production, thirty-eight Ethiopian maize varieties released majorly for three agro-climatic zones over the past thirty-nine, twenty-nine and twelve years for the high altitudes, mid–altitudes and low altitudes, respectively, were conducted at three different research center’s field trials, using randomized complete block design with three replications in 2015 main cropping season to estimate the genetic gains made on yield and yield related traits. The regression analysis indicated average annual and annual relative genetic gains of 62.3 (0.19%), 59.0 (0.57%) and –2.64 (–0.16%) in kg ha–1 yr–1 for grain yields, respectively, at Ambo Plant Protection Research Center (APPRC), Bako National Maize Research Center (BNMRC) and Melkassa Agricultural Research Center (MARC). Correlational analysis on the field studied traits indicated positively significant associations of grain yields with grain filling rate, ear length, number of kernels per row, number of ears per plant, biomass production rate, biomass yield and harvest index; also, negatively significant associations were shown for days to anthesis and days to silking at APPRC. Grain yield showed positively significant associations with ear length, plant height, grain filling rate, thousand kernel weight, biomass production rate and harvest index at BNMRC, while those only with harvest index were shown at MARC. Relatively considerable genetic gains and inconsiderable genetic reductions due to grain yields, grain yield related traits and grain yields associations with the other studied maize breeding traits had been observed across the released maize varieties from the three agro–ecological zones of Ethiopia.