Arnulf Merker

Variation and interrelationships of agronomic traits in Ethiopian tetraploid wheat landraces

SummarySixty tetraploid wheat (Triticum turgidum L.) landrace agrotypes collected from the central highlands of Ethiopia and one commercial check cultivar (Boohai) were evaluated at Akaki experimental station for grain yield and 11 other component traits. The objectives were to estimate phenotypic (PCV) and genetic (GCV) coefficients of variation, broad-sense heritability (H) and genetic advance (GA), and to determine the interrelationships among the various traits. Genotypic differences among the agrotypes were highly significant for all the traits considered. Compared to Boohai, the landrace agrotypes were later in days-to-heading (DTH) and maturity (DTM), and had shorter grain filling period (GFP), lower fertility (KS) and lower 1000-kernel weight (TKW). By contrast, they were superior to Boohai in tiller number (TN), biological yield (BY) and grain yield plant-1 (GYP). Intermediate to high order estimate combinations of GCV, H and GA (as % of the mean) were observed for TN, GYP, number of kernels spike-1 (NKS), harvest index (HI) and TKW. GYP showed a moderate heritability which was higher than GFP, BY and Plant height (PHt). DTH and DTM were strongly correlated, but both were negatively associated with the rest of the traits except PHt. The negative correlation of DTM with GYP was largely indirect via other characters. PHt had either a weak or negative association with the other traits. TN and TKW were positively correlated with GYP, and had high and intermediate direct effects, respectively. These two traits, however, were negatively correlated and showed a substantial counter-balance effect via one another. It appears that, for the short-term, improvement of the Ethiopian wheat landraces may be possible through indirect selection for TN and TKW or direct selection for grain yield per se. In the long-run, crossing programmes between indigenous and introduced germplasm may be necessary.

Chemical composition of the potential new oilseed crops Barbarea vulgaris, Barbarea verna and Lepidium campestre

Barbarea vulgaris, Barbarea verna and Lepidium campestre were selected as potential new oilseed crops. To evaluate the nutritional and technological quality of the seeds, the chemical composition was studied. The major constituents found were dietary fibre, crude fat and crude protein. Barbarea contained about 350 g kg−1 dietary fibre, 295 g kg −1 crude fat and 170 g kg−1 crude protein, while Lepidium contained about 400 g kg−1 dietary fibre, 200 g kg−1 crude fat and 190 g kg−1 protein. The amino acid composition was found to be suitable for human consumption when comparison with the amino acid pattern for high quality protein was made. Fatty acid composition was dominated by erucic acid in B vulgaris (28%) and B verna (50%) and by linolenic acid in L campestre (34%). Insoluble dietary fibres were dominated by Klason lignin in both Barbarea and Lepidium. Uronic acid and glucose residues were also found in large amounts. Soluble dietary fibres were dominated by uronic acid, arabinose and galactose residues. The major glucosinolates found were glucobarbarin in B vulgaris (108 μmol g−1), gluconasturtiin in B verna (106 μmol g−1) and sinalbin in L campestre (110 μmol g−1). No cyanogens were found in any of the seeds. © 1999 Society of Chemical Industry

Quantitative trait diversity in tef [ Eragrostis tef (Zucc.) Trotter] germplasm from Central and Northern Ethiopia

One thousand and eighty tef, Eragrostis tef (Zucc.) Trotter, entries representing 36 populations collected from six central and northern regions of Ethiopia were evaluated at Debre Zeit Agricultural Research Center during the 1995 main season to assess the quantitative trait diversity in the germplasm with respect to collection regions and altitude zones. Hierarchical analysis of variance showed large (p ≤ 0.01) variations within populations, and among populations within regions and altitude zones in all the 14 traits studied. The variations among regions were significant (p ≤ 0.05) for number of main shoot culm nodes, and panicle branches and spikelets. But only days to maturity, number of culm nodes, diameters of the two basal culm internodes, and harvest index depicted discernible (p ≤ 0.05) clinal variability. The 36 populations clustered into six major (75% similarity level) groups consisting of two up to 15 populations. Five principal components (PCs) explained about 81% of the entire phenotypic diversity among the populations. Of these, the first three PCs accounted for about 65% of the gross variance. About 31% of the total variance explained by the first PC alone originated chiefly from variability in main shoot panicle grain yield and length, culm length and diameter of the two basal culm internodes. Likewise, about 23% the variance accounted for by the second PC was due mainly to variations in grain and shoot phytomass yield/plant, and harvest index. Overall, the study demonstrated that tef is a highly versatile crop species and the enormous wealth of quantitative trait diversity in the germplasm indicates immense potential for the genetic improvement of the crop through breeding.

Comparative analysis of genetic diversity of sesame (Sesamum indicum L.) from Vietnam and Cambodia using agro-morphological and molecular markers.

The purpose of this study was to comparatively analyze the genetic diversity of sesame (Sesamum indicum L.) using agro-morphological and molecular markers. Twelve sesame populations collected from three regions in Cambodia and Vietnam were used in this study. A high genetic variation was revealed both by agro-morphological and RAPD markers within and among the 12 sesame populations. The range of agro-morphological trait based average taxonomic distance among populations (0.02 to 0.47) was wider than that of RAPD based genetic distance (0.06 to 0.27). The mean distance revealed by agro-morphological markers (0.23) and RAPD markers (0.22) was similar. RAPD based analysis revealed a relatively higher genetic diversity in populations from South Vietnam as compared to the other two regions. Interestingly, populations from this region also had higher values for yield related traits such as number of capsules per plant, number of seeds per capsule, and seed yield per plant suggesting positive correlation between the extent of genetic variation within population and yield related traits in sesame. A highly significant positive correlation (r = 0.88, P < 0.001) was found between agro-morphological and RAPD markers in estimating the genetic distance between populations. Both methods suggested the existence of a substantial amount of genetic diversity both in the Vietnamese and Cambodian populations. Although both agro-morphological and RAPD markers were found to be useful in genetic diversity analysis in sesame, their combined use would give superior results.

Hybrids between wheats and perennial Leymus and Thinopyrum species

Hexaploid and tetraploid wheats were pollinated by the wild perennial wheat relatives Leymus arenarius, L. mollis, L. racemosus and Thinopyrum junceiforme. Hybrids were obtained from all attempted cross combinations, two of which are reported here for the first time. They are tall and perennial and have the expected chromosome numbers. Strategies for the future use of these hybrids in wheat improvement are discussed and outlined.

Isolation of mildew resistant wheat-rye translocation lines from a double substitution line

A powdery mildew resistant double disomic wheat-rye substitution line carrying rye chromosomes 1R and 2R was crossed with normal bread wheats. The F2 generation was analysed cytologically by C-banding. Wheat-rye chromosome translocations involving both rye chromosomes 1R and 2R were frequent in F2. Lines with translocations of 1R and 2R were harvested separately. After four generations of selfing and selection for mildew resistance and fertility, fully fertile resistant lines were selected and analysed cytologically. Lines with 1BL/1RS and 2BS/2RL translocations were identified. The resistance on chromosome 1RS could not be shown to be different from control varieties carrying the same rye segment, while the resistance on 2RL is much broader than the earlier known 2RL derived resistance in the line Transec.

VARIATION IN SEED OIL COMPOSITION OF SPECIES FROM THE GENERA BARBAREA AND LEPIDIUM

The seed oil composition and content in a number of accessions from species of the genera Barbarea and Lepidium were analysed. The oil from most accessions of B. verna contained more than 50% erucic acid, while the oil from B. vulgaris contained ∼ 30% erucic acid, and 22% each of oleic and linoleic acid. The oil from B. intermedia resembled that of B. verna. The oil content was ∼ 30% in all three species. The oil composition of L. campestre and L. heterophyllum is ∼ 35% linolenic acid and 23% erucic acid. Other Lepidium species had up to 47% linolenic acid in the oil. The oil content of L. campestre and L. heterophylhim was just below 20%, but other species had more than 30% oil in their seeds. The variation in oil composition found within and between species is considered sufficient for the breeding of valuable oil qualities in both genera.

Barley yield increases with undersown Lepidium campestre

Abstract The potential new oil crop Lepidium campestre (field cress) was undersown with long and short row distances in spring barley in three-year trials with eight replications. Plots with no undersowing were used as controls. The purpose was to assess the effect on barley-grain yield of the oil crop and its seed-yield potential. In the plots without undersowing, with long and short row distance of undersown L. campestre the barley-grain yields in the three years were, on average, 5069, 5130, and 5330 kg/ha, respectively. The trials showed a statistically significant positive effect on barley yield of undersowing with short row distance. The average seed yields of L. campestre in the following years were 4697 and 5000 kg/ha for plots with long and short row distance, respectively. The results are positive in relation to possibilities to domesticate this species as a new undersown oil crop for an energy-saving and environmentally friendly cropping system.

Qualitative trait variation in Tef [Eragrostis tef (Zucc.) Trotter] germplasm from Western and Southern Ethiopia

Three thousand tef [Eragrostis tef (Zucc.) Trotter] single panicle derived lines representing 60 populations from western and southern parts of Ethiopia were characterized for panicle form, pigmentation of lemma and anther, caryopsis color, number of main shoot culm internodes, and counts of florets/spikelet at the basal, middle and apical parts of the panicle at Debre Zeit Agricultural Research Center during the 1999 main season. The objectives were to assess the diversity patterns of the germplasm with respect to regions and altitude zones. Among the eight characters, high Shannon-Weaver diversity indices (H’) were noted for anther color (0.71) and number of apical spikelet florets (0.68), and the lowest occurred for panicle form (0.40). Monomorphism (H’ = 0.00) was observed for panicle form, lemma color and number of middle spikelet florets each in three different populations. The overall diversity index for all populations was 0.53. In the analysis of variance of H’ estimates, substantial (p <0.05) regional differences were obtained for lemma color, number of culm internodes, and counts of middle and basal spikelet florets. Clinal variation was significant for panicle form, lemma and seed color, and for the overall mean of traits. Over all traits, mean H’ values declined from 0.60 to 0.46 with an increase in the altitude zone of origin from below 1800 to over 2400 meters above sea level. Overall, the study showed substantial diversity in the test tef germplasm.

Characterisation of mildew resistant wheat-rye substitution lines and identification of an inverted chromosome by fluorescent in situ hybridisation

Seven different mildew resistant wheat lines derived from crosses between triticale and bread wheat were examined by molecular cytogenetics and chromosome C-banding in order to determine their chromosomal composition. Genomic in situ hybridisation (GISH) showed the presence of rye germplasm in all the lines and identified three substitution lines, three double substitution lines and one addition-substitution line. C-banding identified rye chromosomes 1R and 4R in the addition-substitution line, rye chromosomes 1R and 6R in two substitution lines and 1R and 2R in the third line, and rye chromosome 1R in the three substitution lines. Two of the latter lines (7–102 and 7–169) contained a modified form of the chromosome; fluorescent in situ hybridisation (FISH) using five different repetitive DNA-probes showed a pericentric inversion of 1R in both lines. The breakpoints of the 1R inversion were between (1) the 5S rDNA site and the NOR-region on the satellite of the short arm, and (2) between two AAC(5) sites close to the centromere on the long arm. The role of the rye chromosomes in the mildew resistance, the utilisation of the inverted 1R and the significance of the lines in wheat breeding are discussed.