Abstract
Information on genetic progress achieved over time from a breeding program is absolutely essential to develop effective and efficient breeding strategies. Thirty-seven improved lowland sorghum varieties released between 1976 and 2016 and promising advanced lines were evaluated to estimate the genetic progresses made in 40 years of sorghum breeding in Ethiopia. The study was conducted at 2 environments during 2018 cropping seasons in a randomized complete block design with 3 replications. Records taken on grain yield and yield attributes were subjected to statistical analysis. Combined analysis of variance revealed highly significant differences among the genotypes and the test environments for most of the traits, the G×E interaction effects being significant for grain yield. Regression analysis revealed an increase in estimated average annual rate in grain yield potential of 12.2 kg ha-1 year-1 with annual relative genetic change of 0.60% year-1 over the last 40 years of sorghum improvement. Increasing trends along variety release year were also evident for biomass yield, grain yield production per day, biomass production rate and seed growth rate. Stepwise regression analysis revealed that seed growth rate was the most important character, which greatly contributed to the improvement in grain yield. Grain yield was positively correlated with biomass yield, biomass production rate, grain yield production per day, seed growth rate, and thousand seed weight. It is, therefore, strategically advisable that breeding efforts in the future should give due emphasize traits such as seed growth rate. Key words: Sorghum, genetic improvement, grain yield.
Highlights
Sorghum [Sorghum bicolor (L.) Moench, Poaceaea family] 2n = 20) is the 5th most important cereal crop and is the dietary staple of more than 500 million people in 30 countries (FAO, 2011)
The 37 genotypes can be classified into four categories according to their adaptation (i) widely adapted genotypes with above-average grain yield at both locations (9, 16, 19, 21, 22, 27, 28,31, 32, 34 and 37), (ii) genotypes adapted to Sheraro (3, 4, 5, 7, 13, 14, 25, 26, 29 and 35), (iii) genotypes adapted to Miesso (8, 11, 12, 20, 23, 24, 33 and 36) and (iv) genotypes not adapted to any of the locations [(1, 2, 6, 10, 15, 17, 18 and 30) (Figure 1)
Regardless of considerable effort and devotion of resources, the magnitude of genetic progress from sorghum improvement made since its early inception and the associated traits of genetic improvement achieved so far from the same efforts from different years in a common environment have not been studied
Summary
Sorghum [Sorghum bicolor (L.) Moench, Poaceaea family] 2n = 20) is the 5th most important cereal crop and is the dietary staple of more than 500 million people in 30 countries (FAO, 2011). It is grown on 40 million hectare in 105 countries of Africa, Asia, Oceania and the Americas. Sorghum plays an important role as dietary staple for millions of people, especially in arid and semi-arid countries of Africa and Asia. The current sorghum production in Ethiopia is estimated to be 4.3 million tones on an area of 1.8 million hectare of land giving the national average grain yield of 2.4 tones ha-1 (CSA, 2015). Despite the economic importance of sorghum and Ethiopia’s position in terms of domestication and diversity, its productivity has been constrained by wide array of biotic and abiotic stresses such as drought, shoofly, stem borer, midge, grain mold and Striga
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