Genetic Variation Among Portuguese Landraces of ‘Arrancada’ Wheat and <Emphasis Type="Italic">Triticum petropavlovskyi</Emphasis> by AFLP-based Assessment

Portuguese wheat landraces, ‘Arrancada’ were collected from the Aveiro region, Portugal before the 1950s. We found in eight accessions of `Arrancada' hexaploid wheat with the long glume phenotype. We assessed the comparative genetic diversity among Portuguese `Arrancada' wheat and Triticum petropavlovskyi Udacz. et Migusch. using AFLP assays and discuss the origin of long glumed `Arrancada' wheat. With the four primer pairs a total of 4885 visible bands were scored corresponding to 99 AFLP markers as putative loci, of which 55 markers (54%) were polymorphic. UPGMA clustering and PCO grouping showed that long glumed ‘Arrancada’ wheat and T. petropavlovskyi were genetically diverse. Long glumed ‘Arrancada’ hexaploid wheat separated into two clusters (groups) in both the UPGMA dendrogram and in PCO analysis. Four long glumed accessions fell in the cluster of tetraploid wheat. A similar argument could be made for another four accessions which belong to the cluster of hexaploid wheat. The substantial level of genetic variation indicated that long glumed ‘Arrancada’ wheat and T. petropavlovskyi originated independently. It is most likely that the P-gene of long glumed ‘Arrancada’ hexaploid wheat was introduced from T. turgidum ssp. polonicum (L.) Thell. to T. aestivum via natural introgression or breeding. We suggest that the long glumed ‘Arrancada’ hexaploid wheat did not originate from T. aestivum through spontaneous mutation at the P locus     

Assessment of EST-microsatellites markers for discrimination and genetic diversity in bread and durum wheat landraces from Afghanistan

Accurate and reliable means for identification are necessary to assess the discrimination between landraces of tetraploid wheat [T.␣turgidum L. subsp. durum (Desf.) Husn.] and hexaploid wheat (T. aestivum L. em. Thell.). In Afghanistan, farmers usually cultivate mixed landraces, and thus distinction between bread and durum is difficult. A set of 18 microsatellites derived from the DuPont EST-database were used to describe genetic diversity in a sample of 82 Afghan wheat landraces. A total of 101 alleles were detected, with allele number per locus ranging from 2 to 13, and a mean allele number of 6.31. The percentage of polymorphic loci was 89%. The EST-SSRs markers showed different level of gene diversity: the highest Polymorphism Information Content value (0.921) was observed with DuPw 221. Our results demonstrated that with a reasonable number of expressed sequences target microsatellites (EST-SSRs) it is possible to discriminate between T. durum and T. aestivum species of wheat germplasm. Our results showed that EST-databases could be a useful source for species-specific markers and have the potential for new genic microsatellites markers that could enhance screening germplasm in gene banks.     

Analysis of Microsatellite Diversity in Ethiopian Tetraploid Wheat Landraces

The extent and patterns of microsatellite diversity in 141 Ethiopian tetraploid wheat landraces consisting of three species Triticum durum Desf., T. dicoccon Schrank and T. turgidum L. were analyzed using 29 microsatellite markers. A high level of polymorphism and a large number of alleles unique for each species were detected. Compared to emmer (T. dicoccon) and poulard (T. turgidum) wheats, a higher genetic diversity was observed in T. durum. The A-genome was more polymorphic than the B-genome in all the three species. Microsatellites with (GA) _n -repeats had a higher number of alleles than (GT) _n -repeats. A species pairwise comparison was made to determine the percentage of shared alleles and a large number of common alleles among species were observed. Average gene diversity, across the 29 microsatellite loci, was 0.684 for T. durum, 0.616 for T. dicoccon and 0.688 for T. turgidum. Genetic distances were lower between T. durum and T. turgidum (0.26) than between T. durum and T. dicoccon (0.34) or between T. turgidum and T. dicoccon (0.38). A significant correlation (p < 0.01) was found between the number of alleles per locus and the gene diversity in all the three species. Allelic frequency variation was highest between T. turgidum and T. dicoccon (10.62%) and lowest between T. durum and T. turgidum (4.86%). A genetic similarity coefficient of 0.34, 0.46 and 0.37 was found in T. durum, T. dicoccon, and T. turgidum, respectively. The dendogram, which was constructed on the basis of a similarity matrix using the UPGMA algorithm, distinguished all accessions represented in the study.     

Analysis of genetic diversity in Tunisian durum wheat cultivars and related wild species by SSR and AFLP markers

Thirty-four durum wheat cultivars representing the Tunisian durum (Triticum durum Desf.) wheat collection and seven wild species of wheat relatives (Triticum turgidum L., T. dicoccon Schrank., T. dicoccoides (Körn) Schweinf., T. araraticum Jakubz., T. monococcum L., Aegilops geniculata Roth, and Aegilops ventricosa Tausch) were analysed with amplified fragment length polymorphism (AFLP) and microsatellite (SSR) markers. Both marker systems used were able to differentiate durum wheat cultivars from the wild relatives and to specifically fingerprint each of the genotypes studied. However, the two marker systems differed in the amount of detected polymorphisms. The 15 SSR markers were highly polymorphic across all the genotypes. The total number of amplified fragments was 156 and the number of alleles per locus ranged from 3 to 24 with an average of 10.4. Two SSR markers alone, Xwms47 and Xwms268, were sufficient to distinguish all 34 durum wheat genotypes. The five AFLP primer pair combinations analysed yielded a total of 293 bands, of which 31% were polymorphic. The highest polymorphic information content (PIC) value was observed for SSRs (0.68) while the highest marker index (MI) value was for AFLPs (7.16) reflecting the hypervariability of the first and the distinctive nature of the second system. For durum wheat cultivars, the genetic similarity values varied between 31.3 and 81% for AFLPs (with an average of 54.2%), and between 3.6 and 72.7% for SSRs (with an average of 19.9%). The rank correlation between the two marker systems was moderate, with r = 0.57, but highly significant. Based on SSR markers, highest genetic similarity (GS) values were observed within the modern cultivars (37.3%), while the old cultivars showed a low level of GS (19.9%). Moreover, the modern cultivars showed low PIC and MI values. UPGMA Cluster analysis based on the combined AFLP and SSR data separated the wild wheat species from the durum wheat cultivars. The modern cultivars were separated from the old cultivars and form a distinct group.     

Durum wheat cultivation associated with Aegilops tauschii in northern Iran

Hexaploid bread wheat (Triticum aestivum L. ssp. aestivum) is assumed to have originated by natural hybridization between cultivated tetraploid Triticum turgidum L. and wild diploid Aegilops tauschii Coss. This scenario is broadly accepted, but very little is known about the ecological aspects of bread wheat evolution. In this study, we examined whether T. turgidum cultivation still is associated with weedy Ae. tauschii in today’s Middle Eastern agroecosystems. We surveyed current distributions of T. turgidum and Ae. tauschii in northern Iran and searched for sites where these two species coexist. Ae. tauschii occurred widely in the study area, whereas cultivated T. turgidum had a narrow distribution range. Traditional durum wheat (T. turgidum ssp. durum (Desf.) Husn.) cultivation associated with weedy Ae. tauschii was observed in the Alamut and Deylaman-Barrehsar districts of the central Alborz Mountain region. The results of our field survey showed that the T. turgidum–Ae. tauschii association hypothesized in the theory of bread wheat evolution still exists in the area where bread wheat probably evolved.     

Species Diversity in Wheat Landrace Populations from two Regions of Ethiopia

Wheat (Triticum spp.) landrace populations in Ethiopia are mostly species mixtures. However, no quantitative data is available with regard to their species components. We studied here 32 wheat landrace populations originating from two regions (Bale and Wello). A total of 2559 individual plants, 45–110 plants representing each population, were classified into their species components. Five tetraploid (2n = 4x = 28) and one hexaploid (2n = 6x = 42) wheat species were found in mixtures of varying proportions. These included the tetraploids Triticum durum Desf., Triticum turgidum L., Triticum aethiopicum Jakubz., Triticum polonicum L., Triticum dicoccon Schrank and the hexaploid Triticum aestivum L. Also found, however in a rare frequency, in two populations from Wollo was T. durum Desf. convar. durocompactoides Flaksb. (Triticum pyramidale Percival), which is a very dense spiked durum. Discriminant analysis using seven qualitative traits revealed 91.5% correct classification of the wheat species, beak awn and awn length with the most significant importance. Single species were found in eight of the populations; six were for T. durum and two for T. aethiopicum. Two to three species-combinations were the most frequent; a maximum of four species was recorded in one population. The highest diversity index (H′) observed was 0.44. T. durum was the most predominant species. The hexaploid T. aestivum was found in nine of the Wollo populations and, in one population, its frequency reached up to 35.5%. On altitudinal basis, no clear trend of clinal variation was observed both from the frequency distributions and H′ estimates. The results confirmed that Ethiopian wheats, despite the morphological overlaps, could be classified into their species components with high degree of certainty. For the future, therefore, genetic diversity estimations should be dissolved into their species components for more expeditious utilization and conservation of this important genetic resource.     

Comparative genetic diversity of <Emphasis Type="Italic">Triticum aestivum–Triticum polonicum</Emphasis> introgression lines with long glume and <Emphasis Type="Italic">Triticum petropavlovskyi</Emphasis> by AFLP-based assessment

Genetic diversity of a set of introgression lines of Triticum aestivum L./T. polonicum L. with long glume and T. petropavlovskyi Udacz. et Migusch. were analyzed by Amplified Fragments Length Polymorphism (AFLP). Small-scale bulk breeding method was applied throughout until F₆ generation to develop the introgression lines. Thirty-eight hexapolid F₇ plants with long glume phenotype and their parents were subjected to AFLP analysis by four primer combinations. A total of 47 polymorphic loci were detected between the parents, 15 of them were introgressed across the 38 lines. It was hypothesized that approximately 50% of A or B genomes associated polymorphic loci were introgressed. The variation of introgression lines was limited within the diversity between their parents, T. aestivum L. cv. Novosibirskaya 67 (N67) and T. polonicum L. cv. IC12196. N67 was closer to 38 introgression lines than that of IC12196. The UPGMA cluster and principal coordinate analysis (PCO) grouping showed 0.84 to 0.98 similarity values between N67 and the introgression lines. Eleven T. petropavlovskyi accessions were distinguished from introgression lines with UPGMA clusters and PCO groupings, and T. petropavlovskyi was located between the introgressions lines and IC12196. Several introgression lines resembled with T. petropavlovskyi for awning and glume length. The genetic variation among 38 introgression lines was much wider than that of T. petropavlovskyi. We concluded that T. petropavlovskyi was established by intensive selection of hybrid between T. aestivum/T. polonicum.     

Genetic Diversity and Relationships of Wheat Landraces from Oman Investigated with SSR Markers

Little is known about genetic diversity and geographic origin of wheat landraces from Oman, an ancient area of wheat cultivation. The objectives of this study were to investigate the genetic relationships and levels of diversity of six wheat landraces collected in Oman with a set of 30 evenly distributed SSR markers. The total gene diversity, (H_T), conserved in the three durum wheat (Triticum durum desf.) landraces (H_T = 0.46) was higher than in the three bread wheat (Triticum aestivum L.) landraces (H_T = 0.37), which were similar to Turkish and Mexican bread wheat landraces calculated in previous studies. Genetic variation partitioning (G_ST) showed that variation was mainly distributed within rather than among the durum (G_ST = 0.30) and bread wheat (G_ST = 0.19) landraces. Based on modified Rogers’ distance (MRD), the durum and bread wheat landraces were distinct from each other except for a few individuals according to principal coordinate analysis (PCoA). One bread wheat landrace (Greda) was separated into two distinct sub-populations. A joint cluster analysis with other landraces of worldwide origin revealed that Omani bread wheat landraces were different from other landraces. However, two landraces from Pakistan were grouped somewhat closer to Omani landraces indicating a possible, previously unknown relationship. Implications of these results for future wheat landrace collection, evaluation and conservation are discussed.     

Conservation of the genetic variation of Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L.) in synthetic hexaploid wheats (T. turgidum L. s.lat. x T. tauschii; 2n=6x=42, AABBDD) and its potential utilization for wheat improvement

Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L., 2n=2x=14, DD genome) with its diverse range of accessions and distribution provides a unique opportunity for exploiting novel genetic variability for wheat (T. aestivum L.) improvement associated with biotic/abiotic stress factors. From our working collection of 490 T. tauschii accessions we have so far produced 430 different synthetic hexaploids (2n=6x=42, AABBDD) resulting from the chromosome doubling of Triticum turgidum L. s. lat. x T. tauschii F₁ hybrids (each synthetic involving a different T. tauschii accession). We present here our results on hybrid production, plantlet regeneration, cytology, colchicine induced doubling of the 2n=3x=21 chromosome F1 hybrids, seed increase of the doubled progeny and screening for a biotic stress; Cochliobolus sativus Ito and Kuribay (syn. Helminthosporium sativum Pamm. King and Bakke); of 250 of these synthetic hexaploid (2n=6x=42) amphiploids. Application of the direct crossing methodology involving susceptible T. aestivum cultivars with resistant T. tauschii accessions is also alluded to.     

Assessment of genetic diversity in emmer (Triticum dicoccon Schrank) × durum wheat (Triticum durum Desf.) derived lines and their parents using mapped and unmapped molecular markers

In the last few years, the renewed interest for emmer wheat (Triticum dicoccon Schrank) in Italy has stimulated breeding programs for this crop releasing improved genotypes obtained not only by selection from landraces, but even by crosses with durum wheat (Triticum durum Desf.) varieties. The purpose of this work has been to uncover the genetic make-up of some emmer × durum derivatives, specifically by comparing the differences from their parents. Genetic diversity of advanced breeding lines and varieties derived from a durum × emmer cross has been evaluated on the basis of AFLP and SSR markers in comparison with the corresponding emmer and durum wheat parent for addressing the seminal question of how much ‘wild’ variation remains after selection for agronomic type.     

Genetic Variation and Relationships of Pedigree-Known Oat, Wheat, and Barley Cultivars Releaved by Bulking and Single-Plant Sampling

Applications of bulking procedures have played an increasingly important role in molecular characterization of plant germplasm, but little attention has been made to address the effectiveness of detecting genetic variation and inferring genetic relationships via bulking. An analysis was performed here to compare the genetic variation detected and genetic relationships inferred via bulking and single-plant sampling of five oat (Avena sativa L.), wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) cultivars with known pedigrees using amplified fragment length polymorphism (AFLP) markers. Three AFLP primer pairs were applied to screen one bulk and eight single-plant samples of each cultivar and up to 140 AFLP bands were scored for each sample. Analyses of these AFLP data showed bulking revealed AFLP variation up to 21.4% less than corresponding single-plant sampling for these crop species and also introduced up to 2.2% upward and 5.1% downward biases in detecting AFLP variations for each cultivar. The genetic relationships inferred by bulking using the Dice's coefficient, the simple matching coefficient, and the Jaccard's coefficient were largely the same, but differed from those in single-plant samples employing average Dice's coefficient, average simple matching coefficient, and AMOVA-based distance method. All of the inferred genetic relationships were not congruent to the known pedigrees. Clearly, substantial biases could exist in detection of AFLP variation and in inference of genetic relationships from bulk samples, even for closely related germplasm, and more efforts to assess the effectiveness of bulking in inferring genetic variation and relationships are needed for more informative molecular characterization of plant germplasm.     

Genetic analysis of wheat (Triticum aestivum L.) and related species with SSR markers

Genetic diversity among 19 Triticum aestivum accessions and 73 accessions of closely related species was analyzed using simple sequence repeat (SSR) markers. Forty-four out of 497 SSR markers were polymorphic. In total 274 alleles were detected (mean 6.32 alleles per locus). The polymorphic information content (PIC) of the loci ranged from 0.3589 to 0.8854 (mean 0.7538). The D genome contained the highest mean number of alleles (6.32) followed by the A and B genomes (6.13 and 5.94, respectively). The correlation between PIC and allele number was significant in all genome groups (0.7540, 0.7361 and 0.7482 for A, B and D genomes, respectively). Among the seven homologous chromosome groups, genetic diversity was lowest in group 7 and highest in group 5. In cluster and principal component analyses, all accessions grouped according to their genomes were consistent with their taxonomic classification. Accessions with the A and D genomes were clustered into two distinct groups, and AABB accessions showed abundant genetic diversity and a close relationship. Triticum durum and T. turgidum were clustered together, consistent with their morphological similarity. Cluster analysis indicated emmer is closely related to hexaploid wheat. Compared with common wheat, higher genetic variation was detected in spelt, T. aestivum subsp. yunnanense and subsp. tibetanum. In addition, a close genetic relationship between T. polonicum and T. macha was observed. The results of the clustering and principal component analyses were essentially consistent, but the latter method more explicitly displayed the relationships among wheat and closely related species.     

Genetic diversity in Ethiopian hexaploid and tetraploid wheat germplasm assessed by microsatellite markers

The genetic diversity of a subset of the Ethiopian genebank collection maintained at the IPK Gatersleben was investigated applying 22 wheat microsatellites (WMS). The material consisted of 135 accessions belonging to the species T. aestivum L. (69 accessions), T. aethiopicum Jacubz. (54 accessions) and T. durum Desf. (12 accessions), obtained from different collection missions. In total 286 alleles were detected, ranging from 4 to 26 per WMS. For the three species T. aestivum, T. aethiopicum and T. durum on average 9.9, 7.9 and 7.9 alleles per locus, respectively, were observed. The average PIC values per locus were highly comparable for the three species analysed. Considering the genomes it was shown that the largest numbers of alleles per locus occurred in the B genome (18.4 alleles per locus) compared to A (10.1 alleles per locus) and D (8.2 alleles per locus) genomes. Genetic dissimilarity values between accessions were used to produce a dendrogram. All accessions could be distinguished, clustering in two large groups. Whereas T. aestivum formed a separate cluster, no clear discrimination between the two tetraploid species T. durum and T. aethiopicum was observed.     

Comparison of the genetic diversity between <Emphasis Type="Italic">Triticum aestivum</Emphasis> ssp. <Emphasis Type="Italic">tibetanum</Emphasis> Shao and Tibetan wheat landraces (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) by using intron-splice junction primers

In order to evaluate and compare the germplasm resources of wheat in Tibet, we analyzed the genetic diversity of 136 Triticum aestivum ssp. tibetanum Shao and 119 Tibetan wheat landraces (Triticum aestivum L.) by using Intron-Splice Junction (ISJ) primers. The results showed that polymorphism of PCR products were obtained by 33 primer combinations, which accounted for 11% of the 300 primer combinations produced by 26 ISJ primers. A total of 333 stable bands can be amplified from the T. aestivum ssp. tibetanum Shao and 243 bands were polymorphic, which accounted for 72.9% of the total bands. Tibetan wheat Landraces produced 316 stable bands, of which 197 bands were polymorphic. The polymorphic bands accounted for 62.34% of the total bands produced from Tibetan wheat landraces. The genetic diversity of T. aestivum ssp. tibetanum Shao was higher than that of Tibetan wheat landraces in Tibet, suggesting that T. aestivum ssp. tibetanum Shao can be used as important genetic resource for the breeding and genetic improvement of wheat in Tibet. Matrix (1, 0) was generated according to the presence or absence of the bands produced from a particular wheat accession. Clustering and principle coordinates analysis showed that T. aestivum ssp. tibetanum Shao and Tibetan wheat landraces were divided into two groups. We conclude that high polymorphisms produced by ISJ primers can reflect the genetic diversity between T. aestivum ssp. tibetanum Shao and Tibetan wheat landraces.     

Evaluation of genetic diversity of bread wheat landraces from Pakistan by AFLP and implications for a future collection strategy

We used amplified-fragment-length polymorphism (AFLP) markers to evaluate genetic variation in a set of bread wheat (Triticum aestivum L.) landraces and improved materials. Landraces collected from different geographic and agro-ecological zones in Pakistan in 1987, 1989 and 1991 were separated into two groups based on their geographic origins: northern (Himalaya) and south-western (Balochistan) Pakistan. Six AFLP primer combinations detected 453 AFLP markers in the 43 landrace accessions and four high-yield varieties (HYVs). Of these, 225 (49.67%) were rare (shared with < 5% of all accessions). Among these rare alleles, 23 (10.22%) were common in the Himalaya (shared with > 10% of accessions collected there) but were not found in Balochistan. We conclude that there is a higher probability of collecting rare alleles at overall, but which are in contrast locally common ones in the Himalayan region. Gene diversity was 0.17 in the Himalayan group and 0.15 in the Balochistan group. Considerable genetic variability was found in both groups. Accessions from different agro-ecological zones were indistinguishable by cluster analysis, indicating intensive seed trading within the country. Cluster analysis indicated that the landraces and the HYVs are genetically distinct; suggesting that genetic erosion of wheat landraces has been unlikely taken in place. This study provides an example of how analysis of existing materials and data, can serve as a basis for future collection planning and conservation policies.     

Grain Quality of Emmer Wheat Derived Synthetic Hexaploid Wheats

The wild diploid goat grass (Aegilops tauschii Cosson), and the cultivated tetraploid emmer wheat (Triticum turgidum L. subsp. dicoccon (Schrank) Thell.) may be important sources of genetic diversity for improving hexaploid bread wheat (Triticum aestivum L.). Through interspecific hybridization of emmer wheat and Ae. tauschii, followed by chromosome doubling, it is possible to produce homozygous synthetic hexaploid wheat. Fifty-eight such synthetic hexaploids were evaluated for grain quality parameters: grain weight, length, and plumpness, grain hardness, total protein content, and protein quality (SDS-Sedimentation volume, SDS-S). Most synthetics showed semi-hard to hard grain texture. Results showed significant genetic variation among the synthetic hexaploids for protein content, SDS-S values, and grain weight and plumpness. Quality measurement values of synthetic hexaploids were regressed on corresponding values of the emmer wheat parents. With this offspring-parent regression, protein content and SDS-S values explained 8.7 and 28.8%, respectively, of the variation among synthetics, indicating a significant contribution from the emmer wheat parents for these traits. The synthetic hexaploids, in general, had significantly higher protein content (15.5%, on average) and longer grains than ‘Seri M82’, the bread wheat control (13.1% protein content). Synthetics with SDS-S values and grain weights higher than those of ‘Seri M82’ were also identified. Protein content among synthetics showed significantly negative correlations with grain weight and plumpness, but no correlation with SDS-S values. Despite these negative correlations, 10 superior synthetic hexaploid wheats, derived from nine different emmer wheat parents and with above average levels of protein content, SDS-S values, and either grain weight or plumpness, were identified. This study shows that genetic variation for quality in tetraploid emmer wheat can be transferred to synthetic hexaploid wheats and combined with plump grains and high grain weight, to be used for bread wheat breeding.     

Carbon isotope discrimination and water use efficiency in Iranian diploid,tetraploid and hexaploid wheats grown under well-watered conditions

Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C₃ crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency for grain and biomass production (WUE_G and WUE_B, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as within bread wheat. It was also positively correlated to stomatal frequency. The highest WUE_G and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUE_B and biomass than durum wheat. WUE_G and WUE_B were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUE_G was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUE_G. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships between WUE_G and its different components (water consumed, transpiration efficiency and carbon partitioning).     

Natural and human selection for purple-grain tetraploid wheats in the Ethiopian highlands

Summary Purple-grain tetraploid wheats (Triticum turgidum L.) are widely cultivated in the Ethiopian highlands despite the claim that they have lower industrial quality properties and market prices than the white or red/brown seed-colour types. In an attempt to find a possible explanation for this, the three seed-colour groups were compared for grain yield, other 11 agronomic traits and protein content. Five traits displayed significant differences between seed colour groups where the purple-seed was superior; earlier maturity, shorter height, and higher fertility, tillering capacity and harvest index. Most of these are important adaptive traits to waterlogging stress on dark-clay soils (pellic vertisols) where the great bulk of the Ethiopian tetraploid wheats have been grown. Furthermore, among the three seed-colour groups, purple-seed wheat has the best malting quality for the preparation of arekie, a locally distilled spirituous liquor. It, therefore, appears that both natural and human selections have been reponsible for their continued cultivation. Hence, the notion that purple-seeded wheat is the “least preferred” should be interpreted carefully not to necessarily address the whole community in Ethiopia. As to their taxonomy, all tetraploid wheat taxa (T. turgidum L. sensu lato, 2n = 4x = 28) that are found in Ethiopia, with the possible exception of T. dicoccon Shrank (locally known as Adja), may possess the purple pericarp-colour, although in varying frequencies; very low inT. polonicum L., and high inT. carthlicum Nevski andT. durum Desf.     

Evaluating landraces of bread wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. for tolerance to aluminium under low pH conditions

Bread wheat (Triticum aestivum L.) landraces held within ex situ collections offer a valuable and largely unexplored genetic resource for wheat improvement programs. To maximise full utilisation of such collections the evaluation of landrace accessions for traits of interest is required. In this study, 250 accessions from 21 countries were screened sequentially for tolerance to aluminium (Al) using haematoxylin staining of root tips and by root regrowth measurement. The staining test indicated tolerance in 35 accessions, with an intermediate response to Al exhibited in a further 21 accessions. Of the 35 accessions classified as tolerant, 33 also exhibited increased root length following exposure to Al. The tolerant genotypes originated from Bulgaria, Croatia, India, Italy, Nepal, Spain, Tunisia, and Turkey. AFLP analysis of the 35 tolerant accessions indicated that these represent diverse genetic backgrounds. These accessions form a valuable set of germplasm for the study of Al tolerance and may be of benefit to breeding programs for expanding the diversity of the gene pool from which tolerant cultivars are developed.