Becker et al., 1999;Miller, 1999). Studies in B. napus, B. rapa, and B. juncea have indicated high levelsHeterosis is commercially exploited in rapeseed (Brassica napus of heterosis. Pradhan et al. (1993) reported 29 to 92% L.) and its potential use has been demonstrated in turnip rape (B. rapa L.) and Indian mustard (B. juncea L.). In Ethiopian mustard heterosis over the best-yielding parents in B. juncea by (B. carinata A. Braun), however, information regarding heterosis has crossing parents of Indian and exotic origin. Banga and not been previously reported. This study, therefore, was conducted Labana (1984) reported up to 200% heterosis in B.to generate information on heterosis and combining ability in B.juncea. Brandle and McVetty (1989) reported high-parcarinata. Nine inbred parents and their 36 F 1 s, obtained by half-diallel ent heterosis reaching 120% for seed yield in B. napus. cross, were evaluated for 12 traits at three locations in Ethiopia.In summer turnip (B. rapa), high-parent heterosis for Analysis of variance showed the presence of significant heterosis for seed yield reaching 60% was reported by Schuler et al. all the traits. Seed yield showed the highest relative mid-parent hetero-(1992) and Falk et al. (1994). Consequently, in several sis that varied from 25 to 145% with a mean of 67%. Relative highcountries hybrid cultivars played an important role in parent heterosis for seed yield varied from 16 to 124% with a mean of 53%. General combining ability (GCA) effects were predominant the expansion of B. napus cultivation (Becker et al., in all traits except secondary branches and pods per plant. Specific 1999; Miller, 1999). Heterosis can be partially utilized combining ability (SCA) was significant for days to flowering, secondalso by developing synthetic cultivars (Becker et al., ary branches, pods per plant, pod length, seeds per pod, 1000-seed 1998). weight and oil content. Interaction effects of GCA ϫ location were Although combining ability studies in oilseed Brassica significant for all traits except days to flowering, days to maturity, spp. are scanty, most of these studies emphasized the and oil content. All traits had significant SCA ϫ location interaction preponderance effect of GCA on yield and most of the effects. GCA effect for seed yield was positively correlated with F 1 yield components indicating the importance of additive performance (r ϭ 0.77) and absolute mid-parent heterosis (r ϭ 0.67).

Predicting heterosis and F1 performance from the parental generation could largely enhance the efficiency of breeding hybrid or synthetic cultivars. This study was undertaken to determine the relationship between parental distances estimated from phenotypic traits or molecular markers with heterosis, F1 performance and general combining ability (GCA) in Ethiopian mustard (Brassica carinata). Nine inbred lines representing seven different geographic regions of Ethiopia were crossed in half-diallel. The nine parents along with their 36 F1s were evaluated in a replicated field trail at three locations in Ethiopia. Distances among the parents were calculated from 14 phenotypic traits (Euclidean distance, ED) and 182 random amplified polymorphic DNA (RAPD) markers (Jaccard's distances, JD), and correlated with heterosis, F1 performance and GCA sum of parents (GCAsum). The correlation between phenotypic and molecular distances was low (r=0.34, P< or =0.05). Parents with low molecular distance also had low phenotypic distance, but parents with high molecular distance had either high, intermediate or low phenotypic distance. Phenotypic distance was highly significantly correlated with mid-parent heterosis (r=0.53), F1 performance (r=0.61) and GCA (r=0.79) for seed yield. Phenotypic distance was also positively correlated with (1) heterosis, F1 performance and GCA for plant height and seeds plant(-1), (2) heterosis for number of pods plant(-1), and (3) F1 performance for 1,000 seed weight. Molecular distance was correlated with GCAsum (r=0.36, P< or =0.05) but not significantly with heterosis and F1 performance for seed yield. For each parent a mean distance was calculated by averaging the distances to the eight other parents. Likewise, mean heterosis was estimated by averaging the heterosis obtained when each parent is crossed with the other eight. For seed yield, both mean ED and JD were significantly correlated with GCA (r=0.90, P< or =0.01 for ED and r=0.68, P< or =0.05 for JD) and mean heterosis (r=0.79, P< or =0.05 for ED and r=0.77, P< or =0.05 for JD). In conclusion, parental distances estimated from phenotypic traits better predicted heterosis, F1 performance and GCA than distances estimated from RAPD markers.

As an oilseed crop, the cultivation of Ethiopian mustard (Brassica carinata) is restricted only to Ethiopia. Even though geographic diversity is a potent source of allelic diversity, the extent of genetic diversity among germplasm material of Ethiopian mustard from different countries has not been assessed. Forty-three accessions, comprising 29 accessions from eight different geographic regions of Ethiopia and 14 exotic accessions from Australia, Pakistan, Spain, and Zambia were analysed for their genetic diversity using random amplified polymorphic DNA (RAPD) technique. A set of 50 primers yielded a total of 275 polymorphic bands allowing an unequivocal separation of every Ethiopian mustard accession. The usefulness of the 50 RAPD primers in measuring heterozygousity and distinguishing accessions was variable such that polymorphic information content (PIC) varied from 0.05 to 0.40, band informativeness (BI) from 0.05 to 0.65 and primer resolving power (RP) from 0.15 to 6.83. Jaccard's similarity coefficients ranged from 0.44 to 0.87 indicating the presence of a high level of genetic diversity. On the average, Australian and Ethiopian accessions were the most similar while, Spanish and Zambian accessions were the most distant ones. Cluster analysis grouped the 43 accessions into four groups, which has quite a high fit (r = 0.80) to the original similarity matrix. With no prior molecular information, the RAPD technique detected large genetic diversity among the 43 accessions from five different countries and their grouping by dendrogram and principal coordinate analysis (PCoA) was inclined towards geographic differentiation of RAPD markers. Conversely, RAPD differentiation along geographic origin was not apparent within the Ethiopian accessions.

Little is known on maize germplasm adapted to the African highland agro-ecologies. In this study, we analyzed high-density genotyping by sequencing (GBS) data of 298 African highland adapted maize inbred lines to (i) assess the extent of genetic purity, genetic relatedness, and population structure, and (ii) identify genomic regions that have undergone selection (selective sweeps) in response to adaptation to highland environments. Nearly 91% of the pairs of inbred lines differed by 30–36% of the scored alleles, but only 32% of the pairs of the inbred lines had relative kinship coefficient <0.050, which suggests the presence of substantial redundancy in allelic composition that may be due to repeated use of fewer genetic backgrounds (source germplasm) during line development. Results from different genetic relatedness and population structure analyses revealed three different groups, which generally agrees with pedigree information and breeding history, but less so by heterotic groups and endosperm modification. We identified 944 single nucleotide polymorphic (SNP) markers that fell within 22 selective sweeps that harbored 265 protein-coding candidate genes of which some of the candidate genes had known functions. Details of the candidate genes with known functions and differences in nucleotide diversity among groups predicted based on multivariate methods have been discussed.