Genetic Gain in Grain Yield Potential and Associated Traits of Tef [Eragrostistef (Zucc.) Trotter] in Ethiopia

Abstract

Evaluation of varieties from different years in a common environment is the most direct of the several methods that have been used to estimate breeding progress. 33 tef varieties released in Ethiopia since 1970 till now were evaluated at DebreZeit and Melkassa Agricultural Research Centers to estimate the amount of genetic gain made over time in grain yield potential and associated characters. The varieties were laid out in a randomized complete block design with three replications in 2012 cropping season. Analysis of variance revealed significant differences among varieties for all traits except hundred seed weight on both locations.Grain yield was increased from 3848.68 kg ha-1 to 4934.4kg ha-1 over the past 42 years. The average annual rate of increase per year for the period of 1970-2012 was estimated from the linear regression of mean grain yield on year of variety release was 21.53 kg ha-1 with a relative genetic gain of 0.56% year-1 which was highly significantly different from zero. Grain yield potential of tef has not attained plateau in Ethiopia. Thus, development of higher yielding varieties of tef should continue to increase tef grain yields if past trends pretend the future. Biomass yield also showed highly significantly increase with annual genetic gain of 73.74 kg ha-1 year-1. Similarly grain yield per day and biomass production rate at both locations showed highly significantly different from zero except biomass production rate at Melkassa which was significantly increased with year of release. On the contrary, days to panicle emergency, days to maturity and lodging index at both locations showed non- significant decreasing trend over years. Linear regression also indicated that significant improvements in yield panicle-1 and panicle weight across location and at both location respectively. No marked changes were observed in days to seedling emergency, harvest index, plant height, panicle length and hundred seed weight during the study period which implied that tef improvement effort has failed to bring a substantial progress on these traits. Grain yield was significantly and positively associated with biomass yield, yield panicle-1, grain yield day-1 and biomass production rate, where as there was no significant correlation between grain yield and phenologic traits, harvest index, plant height, hundred seed weight, panicle weight, lodging index and panicle length. Stepwise regression analysis revealed that most of the variation in grain yield of tef was caused by biomass yield and harvest index. In order to see the impact of the achievement in the genetic progress of tef research, it is imperative to undertake large scale popularization of the released varieties.