Genetic diversity analysis and genotpe x environment interaction in Ethiopian mustard (Brassica carinata A. Braun)

English: Ethiopian or Abyssinian mustard (Brassica carinata A. Braun) is one of the most important oil crops in Ethiopia. Apart from its phylogenetic relationships with other members of the genus Brassica, little information is available for this species. This study explored the genetic diversity and genotype x environment interaction for its possible use in genetic conservation and breeding. Geographical patterns of morphological variations were studied on 258 accessions of B. carinata randomly sampled from different parts of the country using Shannon Weaver diversity index ( H') to estimate the phenotypic diversity index for six morphological traits. The results revealed that the mean diversity index (H') across regions of the country was 0.72±0.06. Polymorphism was high for some of the traits. The mean diversity index (H') for the country across altitudinal classes was H' = 0.71 ± 0.07. Highest mean diversity index was recorded from areas ranging from 2600-280 masl. The centres of diversity appears to be Shewa, Bale and Arsi provinces with due consideration of altitudes. Further exploration and in situ conservation efforts should be undertaken in these regions. Brassica carinata possesses a number of agronomic advantages over other oil seed crops with similar ecological adaptation. However, the oil is considered low quality. Although efforts have been made to improve its quality, much has to be done to use natural variations that might exist within the species for fatty acid composition. The objectives of this study were to determine the oil content and fatty acid composition to determine the range of genetic diversity for these traits, and to select genotypes that can be used in crosses to improve these traits. Ninety-eight Ethiopian grown genotypes were analyzed by CGC to study the variability of fatty acid composition. The analysis revealed a wide variation in fatty acid composition; twenty-six fatty acids were identified. The predominant fatty acids were erucic (6.91-35.05%), linoleic (17.21-28.53%),α -linolenic (10.50-22.52%), and oleic (8.91-24.64%), followed by gadoleic (1.22-10.24%) and palmitic (3.38-16.42%). Palmitic acid had significant positive correlations with stearic acid. Erucic acid showed significant and negative linear correlations with palmitic, stearic, vaccinic, oleic, linoleic, α-linolenic acids and positive correlation with eicosenoic acid. The high oil yielding genotypes were relatively richer in erucic acid content. Oil content ranged from 25 to 48%. Genetic diversity analysis within B. carinata has not been examined with molecular markers. The objective of this study was to investigate the genetic relationships among 39 B. carinata genotypes by the AFLP markers. This study explored the amount of genetic variation for possible use in breeding. Thirty-nine genotypes of B. carinata were analysed using six AFLP primer combinations. A total of 189 polymorphic markers were scored, with an average of 32 markers per primer combination. GDE ranged from 0.346 to 0.639, with a mean of 0.504 ± 0.002. Polymorphism rates ranged from 50 to 80%. UPGMA cluster analysis revealed seven genetically distinct groups of genotypes. The GE interaction and the stability of 14 B. carinata genotypes for seed yield were evaluated at four rain-fed locations, over three years in north-western Ethiopia. The objectives were to estimate the component of variance associated with the first and second order interactions and to determine their effects and to measure the genotypes' stability using different stability statistics; and to compare the stability statistics. The analysis of variance test revealed that the main effects due to years, locations, and the first order interactions (year x location) as well as second order interactions (genotype x year x location) were highly significant. The genotype x location interaction was not significant. This suggests the necessity for increased emphasis on multiple years of testing than more locations. The estimates of variance components involving first order interaction of genotype x year, genotype x location and the error variance were very small. The variance components of the main effects of the genotype and second order interaction of genotype x location x year were very high. positive correlation with eicosenoic acid. The high oil yielding genotypes were relatively richer in erucic acid content. Oil content ranged from 25 to 48%. Genetic diversity analysis within B. carinata has not been examined with molecular markers. The objective of this study was to investigate the genetic relationships among 39 B. carinata genotypes by the AFLP markers. This study explored the amount of genetic variation for possible use in breeding. Thirty-nine genotypes of B. carinata were analysed using six AFLP primer combinations. A total of 189 polymorphic markers were scored, with an average of 32 markers per primer combination. GDE ranged from 0.346 to 0.639, with a mean of 0.504 ± 0.002. Polymorphism rates ranged from 50 to 80%. UPGMA cluster analysis revealed seven genetically distinct groups of genotypes. The GE interaction and the stability of 14 B. carinata genotypes for seed yield were evaluated at four rain-fed locations, over three years in north-western Ethiopia. The objectives were to estimate the component of variance associated with the first and second order interactions and to determine their effects and to measure the genotypes' stability using different stability statistics; and to compare the stability statistics. Mean yield over all locations and years ranged from 1304 to 1541 kg/ha by PGRCIE 210406 and PGRCIE 21163 respectively. The regression of yield on the environmental index resulted in a regression coefficient value ranging from 0.7488- 1.2288. The deviation from regression was non significant for all genotypes. The first two interaction principal component axes of the additive main effects and multiplicative interaction (AMMI) model together accounted between 35.7% and 54.3% of the total genotype x environment interaction of sum of squares for seed yield. The stability analyses identified PGRC/E 20017 and PGRC/E 20112 as more stable genotypes, while PGRC/E 21169 and (4DxZEM-1) x (ZEM-1-AD/88) were specifically adapted to some environments. Spearman's coefficient of rank correlation was performed for each of the possible pair wise comparisons of different stability statistics. Significant rank correlations were observed among some of the stability statistics. These significant rank correlations indicated their effectiveness in detecting stable genotypes over a range of environments. The hierarchical clustering of AMMI adjusted mean yield using UPGMA clustering method grouped the genotypes into five genetically distinct clusters and the environments into three heterogeneous clusters.