Genotype by environment interactions (G x E) and stability analyses of malting Barley (Hordeum distichon L.) genotypes across northwestern Ethiopia

Seven genotypes were evaluated under rainfed conditions at seven different locations across northwestern Ethiopia with the objectives of investigating phenotypic performance, determining the magnitude of effect of genotypes, environments, and their interactions on important traits and identifying stable malting barley genotype. The highest mean grain yield was recorded at Geregera followed by Debretabor but the lowest at Motta and Burie. Among the genotypes Miscale-21 gave the highest mean grain yield followed by HB-1533. Miscale-21 and Arna provided high kernel protein whereas HB-1533 the least. High thousand kernel weight and hectoliter weight was obtained at Laygaint,, whereas Adet was the least with regard to these traits. Miscale-21 and HB-1533 had high thousand kernel and hectoliter weight. All genotypes fulfill the requirements for germination capacity. Furthermore, G x E interaction was significant for grain yield. Partitioning of the G x E interaction using AMMI showed the first IPCA axis alone explained most of the sum of squares. Moreover, the biplot of AMMI revealed clear insight into the specific and general adaptation of genotype across locations. According to stability analysis measures genotype HB-1533 was the most stable for grain yield whereas Miscale-21 showed specific adaptation in low potential environments

Genetic variation for drought resistance in small red seeded common bean genotypes

Common bean ( Phaseolus vulgaris L.) productivity is low in major growing regions of Ethiopia mainly due to drought, caused by low and erratic rainfall. A field experiment was carried out at Gofa in Southern Ethiopia, to assess genetic variability for drought resistance in forty-nine small red seeded common bean genotypes of both local and foreign origin. The genotypes were evaluated under two soil moisture regimes, non-stress (NS) and drought stress (DS). Drought stress was initiated at flowering by withholding application of irrigation water. The average linkage method of clustering grouped the forty-nine genotypes grown under drought stress condition in five clusters. The maximum distance was found between Cluster I and Cluster III. Pattern of variation examined through principal component analysis (PCA) involving morpho-physiological traits showed that the first four PCs accounted for more than 74% of the total variation, of which 59.9% was contributed by the first two PCs. The first principal component alone explained 49.9% and was highly correlated with seed yield, harvest index and geometric mean. The second PC explained 9.7% of the total variation and was highly correlated with days to maturity and drought susceptibility index. Both PCs had higher relative contributions to the total diversity and were the ones that most differentiated the genotypes.La productivit\ue9 du haricot commun ( Phaseolus vulgaris L.) est basse dans beaucoup de r\ue9gions productrices ethiopiennes principalement due \ue0 la s\ue9cheresse et aux pluies irr\ue9guli\ue8res. Un essai sur terrain \ue9tait men\ue9 \ue0 Gofa au Sud de l\u2019Ethiopie, pour \ue9valuer la variabilit\ue9 g\ue9n\ue9tique, pour r\ue9sistance \ue0 la s\ue9cheresse dans quarante quatre g\ue9notypes de petits grains de haricot rouges, tous d\u2019origine locale et exotique. Les g\ue9notypes \ue9taient \ue9valu\ue9s sous deux r\ue9gimes d\u2019humidit\ue9 de sol, non-stress (NS) et stress hydrique (DS). Le stress hydrique \ue9tait initi\ue9 \ue0 la floraison par la r\ue9duction de l\u2019eau d\u2019irrigation. A l\u2019aide de la m\ue9thode de la moyenne des liens des groupements, quarante neuf g\ue9notypes plant\ue9s en condition de stress hydrique \ue9taient class\ue9s en cinq groupes. La distance maximale \ue9tait trouv\ue9e entre le groupe-I et le groupe-III. Le mode de variation examin\ue9 par l\u2019analyse de la composante principale (PCA) impliquant des traits morpho-physiologiques a montr\ue9 que les quatre premiers PCs comptaient pour plus de 74% de la variation totale parmi lesquels 59.9% \ue9taient induits par les deux premiers PCs. Le premier composant principal expliquait seul 49.9% et \ue9tait hautement correl\ue9 avec le rendement en grains, l\u2019index de r\ue9colte et la moyenne g\ue9om\ue9trique. Le second PC a expliqu\ue9 9.7% de la variation totale et \ue9tait hautement corr\ue9l\ue9 avec les jours \ue0 la maturit\ue9 et l\u2019index de susceptibilit\ue9 \ue0 la s\ue9cheresse. Tous les PCs offraient des contributions \ue9lev\ue9es \ue0 la diversit\ue9 totale et \ue9taient celles qui avaient diff\ue9renci\ue9es le plus les g\ue9notypes

Combining Ability Analysis for Bread Wheat (Triticum Aestivum L.)

 Choice of promising genotypes from a diverse genetic base and subsequent utilization for hybridization is one of the strategies for improving productivity of bread wheat. The data from eight parents and their F1 progenies of half-diallel crosses were analyzed for combining ability for yield and yield related traits in triplicate randomized complete block design in 2005 at Sinana, south-east Ethiopia. Significant differences among all the genotypes were apparent for all traits, except for biomass per plant. Both GCA and SCA mean squares revealed significant differences in plant height, harvest index, grain yield per plant, 1000-kernel weight and maturity traits, indicating the important of both additive and non-additive gene actions in the inheritance of these traits with the predominant effect of non-additive gene action. For the remaining traits, only mean square due to GCA showed significant variation, indicating the greater importance of additive gene action in controlling the inheritance of these characters. Abola gave highly significant GCA effects in the desirable direction and was the best general combiner for most of the traits,followed by Galema and Sofumer, while Dashen was the only parentwhich showed significant positive GCA effect for grain yield per plant. Cross combinations of Dashen x Galema, Abola x Dure, Dashen x Meda-Welabu, Abola x Galema, and Galema x Dure, exhibited significant SCA effects in the desired direction for at least two and, at most, for four traits, for which SCA variance showed significant differences. Hence, these crosses revealed possibility for commercial exploitation of heterosis as well as selection of potential homozygous lines from transgressive segregants for improvement of yield levels of bread wheat

Estimation of Heterosis for Yield and Yield Related Traits in Bread Wheat (Triticum aestivum L.)

Selection of promising genotypes from diverse genetic base and their subsequent utilization for hybridization is one of the strategies for improving  productivity of bread wheat (Triticum aestivum L.) in Ethiopia. Thirty-six genotypes were evaluated in triplicated randomized complete blocks to estimate  the extent of mid and better parent heterosis for yield and yield related traits using 8 × 8 half-diallel cross during the 2005 season at Sinana, Ethiopia.  Significant differences among all the genotypes were noticed for all traits, except for biomass per plant.. The highest heterosis over mid and better  parent as well as economic heterosis for grain yield was recorded in Dashen × MedaWelabu hybrid with corresponding values of 63%, 52% and 44%,  respectively. The crosses that showed heterosis for grain yield were also heterotic for most of the yield related traits. The negative heterosis observed for  plant height and maturity traits in most of the crosses was in the desired direction. The negative mid and better parent heterosis observed for tillers per  plant and spike traits in several of the crosses, however, was undesirable heterosis in bread wheat improvement. The study revealed good scope for  commercial exploitation of heterosis as well as selection of pure lines among the progenies of heterotic F1s for improvement of yield in bread wheat.&nbsp

Genotype x Environment Interaction and Yield Stability of Maize

Maize cultivars vary in their response to variable environmental conditions. Twenty maize cultivars were tested at nine locations in Ethiopia (1100 – 2240 masl) in randomized complete block design with three replications for two years to study the nature and magnitude of genotype x environment (G x E) interaction and phenotypic yield stability of the cultivars. Analysis of variance and stability analysis were computed. Variances due to genotypes, years, locations, genotype x year, genotype x location and genotype x year x location interaction were significant (P<0.01). Most of the cultivars had significant deviation mean square (S2di), implying that these cultivars had unstable performance across the testing environments. However, Additive Main Effect and Multiplicative Interaction (AMMI) analysis showed Gibe-1 (mean yield, 7.40 t ha-1) had relatively stable performance across the environments. None of the cultivars were the best for grain yield in all environments. BH-660 (mean grain yield, 8.14 t ha-1) had a relatively good performance in the mid- to high-altitude (1650 – 2240 m above sea level) areas whereas BH-140 (mean grain yield, 6.65 t ha-1) had a good performance in the low-mid to mid-altitude (1100 – 1650 m above sea level) areas, indicating the possibility of developing specific cultivars adapted to mid- and high- or low-mid and mid-altitude areas. However, the top yielding cultivars at each maize agro-ecology were specifically adapted, indicating that, for high yield potential in each maize agro-ecology, a specific breeding program is necessary

Advances in Improving Harvest Index and Grain Yield of Maize in Ethiopia

The local maize varieties are inefficient in transferring assimilates to the ear sink and as a result they are low yielding. To replace these low yielding local varieties by high yielding ones, different breeding methods have been used in Ethiopia. This study was undertaken to compare improved maize varieties released in Ethiopia for their harvest index and other important agronomic traits. Twelve improved maize varieties which were released from 1970s to 1990s in Ethiopia and 8 breeding populations were tested in a randomized complete block design at Bako Agricultural Research Centre under sub-optimum and optimum soil fertility conditions in 1997 and 1998. The analysis of variance for harvest index and other important agronomic traits showed significant differences (P<0.01) among the varieties. The mean harvest index varied from 31.1% (Bako composite) to 45.0% (BH-540), indicating wide differences among the varieties in partitioning the photosynthate into grain and vegetative plant part. The mean grain yield also varied from 4.3 t ha-1 (EAH-75) to 7.2 t ha-1 (BH-660). All the varieties released in the 1990s had a better harvest index than the old maize composites, indicating the breeding progress made was successful for both grain yield and harvest index. Further progress in maize breeding to improve harvest index and grain yield would be possible with the use of refined breeding methods and tools

Genotype-environment interaction and stability analysis for grain yield of maize (Zea mays L.) in Ethiopia

Fifteen maize genotypes were tested at nine different locations in 2005 under rainfed condition to determine stable maize genotypes for grain yield and determine genotypes with high yield and form homogenous grouping of environments and genotypes. The experiment was conducted using Randomized Complete Block Design with three replications. There was considerable variation among genotypes and environments for grain yield. Stability was estimated using the Additive Main Effects and Multiplicative Interactions (AMMI). Based on the stability analysis, genotypes 30H83, BH-540, Ambo Synth-1, AMH-800 and BHQP-543 were found to be stable for grain yield. The first two Interaction Principal Component axis (IPCA1 and IPCA2) were significant (