Variation of leaf esterases in some Ethiopian tetraploid wheat landraces

Summary Esterase isozymes of tetraploid wheat landraces originating from four localities in the central highlands of Ethiopia were studied using the horizontal starch gel electrophoresis. The landraces studied consisted of 60 Triticum turgidum L., one T. dicoccon Schrank, one T. polonicum L. and an improved local cultivar. One introduced durum cultivar was also included for comparison.A total of 12 esterase zymograms were detected in the landraces. Among these, the types C, A and G were found to be the most prevalent. The esterase isozymes exhibited high variation in the landraces. The esterase zymograms of the introduced durum cultivar and T. dicoccon differed from those of the landraces while the patterns attained in T. polonicum and the improved local cultivar were identical to those of the other landraces.The total number of bands detected was 10, of which 2 were rare, being displayed by only 1 pattern each. The band content of zymograms was in the range of 3–6 and the average was 4. The unique bands were observed in zymograms with both high and low prevalences in the landraces. Two zymograms, including zymogram C which had the highest frequency, occurred in all the localities. The high yielding landraces displayed 4 of the zymograms, one of which belonged to two of the zymograms with widest distribution.     

Diversity and geographic distribution of adaptive traits in Triticum turgidum L. (durum group) wheat landraces from Turkey

Summary A collection of 2,420 accessions derived from single-spike population samples of durum wheat landraces collected in 1984 from 172 sites in 28 provinces in Turkey was evaluated for nine adaptive traits at the ICARDA research station at Tel Hadya, near Aleppo, Syria. Differentiation of these accessions among provinces was found for number of days to heading, maturity, grain-filling days, as well as for plant height, peduncle length, number of spikelets per spike, spike length, awn length, and kernel weight. The first three canonical variables accounted for 90% of the total variance. Canonical analysis also revealed significant correlations to province mean temperatures, altitude, latitude, and length of the growing season, but not with total seasonal rainfall. Eight distinct groups of provinces were identified by cluster analysis. These clusters had both geographical orientation to eastern and western Turkey and to agroecological zonation for clusters having both eastern and western provinces. Accessions were found with high kernel weight, early heading and maturity, and awnless spikes which could be utilized in crop improvement programs targeted at either favorable or stressed environments.     

Patterns of morphological diversity in tetraploid wheat (Triticum turgidum L.) landraces from Ethiopia

Thirty‐four tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace populations collected from four regions in Ethiopia, and consisting of 4099 entries were characterized for glume colour, glume pubescence, beak awn, seed colour and spike density. The main objective was to analyse the diversity and distribution of these traits on the basis of administrative regions and altitudinal gradients. The Shannon‐Weaver Diversity Index (H') was used to estimate the magnitude of diversity. With the exception of spike density, all characters were polymorphic in all regions and most altitude groups. However, clinal patterns were observed in only a few cases. At the population level, the mean H’ varied from completely monomorphic (H’ = 0.00) to highly polymorphic (H’ = 0.80 ± 0.07). The highest diversity was found in regions with relatively better climatic conditions and in optimal altitude ranges. On country basis, seed colour (H’ = 0.98) and spike density (H’ = 0.43) displayed the highest and the lowest diversity indices, respectively. Spike density was the only character that exhibited significant differences (P<0.01) both “between regions”; and “between altitude groups”;. Across characters, most of the variance was due to the lowest hierarchy, the “within‐population”; component. The “between region”; and “between altitude group”; variances were significant, but spike density alone was responsible for the differences. The overall mean H’ for Ethiopia was 0.77 + 0.09 and did not seem to have reduced appreciably within the past 25 years or so, when compared to previous estimates.     

Diversity and geographic distribution of stem solidness and environmental stress tolerance in a collection of durum wheat landraces from Turkey

Variation and geographic distribution of stem solidness and environmental stress tolerance were assessed under dryland conditions in a collection of 2420 durum wheat landrace morphotypes collected in 28 administrative provinces of Turkey. The former trait is known to confer resistance to wheat stem sawfly – a serious pest insect in West Asia and North Africa. Both characters were scored on a visual five-level scale. Score mean values and frequency distributions in the different provinces were significantly different for both traits according to analysis of variance and chi-square test, respectively. Two groups of provinces emerged with high frequency of solid-stemmed, and hollow-stemmed accessions, respectively. The former could be of interest in durum wheat breeding against the sawfly. The group of solid-stemmed province germplasms was collected at lower altitude than the other, being also different on average for higher temperatures and evapotranspiration, and shorter growing season at sites of origin. Overall frequency of morphotypes tolerant to stress conditions prevailing in the evaluation site was rather low (10%). This low frequency may be due to low adaptation of materials in this harsher environment than those of origin where rainfall is usually higher and temperatures markedly lower. Nonetheless, differences among provinces in frequency distribution of stress tolerant morphotypes were evidenced. The relatively more tolerant gene pools originated either along the western coast or in the southern part of the country, along the Fertile Crescent. The least tolerant province germplasms originated either in the North along the Black Sea or in the highlands of the eastern Anatolian Plateau. Germplasm from provinces Malatya and Izmir combined good levels of both stem solidness and stress tolerance.     

Phenotypic diversity of durum wheat (<Emphasis Type="Italic">Triticum durum</Emphasis> Desf.) from Jordan

Durum wheat landrace genotypes are disappearing from the main wheat areas in Jordan, because of spreading of new uniform cultivars and the serious reduction in wheat cultivation. This study was conducted to evaluate genetic diversity in durum wheat landraces from Jordan and to identify desirable agronomic traits. Landraces were collected from two target areas: Ajloun and Karak. The collected material was grown under rainfed conditions using an augmented design with five blocks and four repeated check cultivars. Data were collected for 14 morphological and agronomic traits. Phenotypic diversity index (H′) was estimated, and the relationships among accessions were measured using cluster analysis and dendrogram similarity matrix. The results revealed the presence of a wide range of variability among landraces., which possess high levels of variability for biological yield, fertile tillers, number of seeds per spike, seed weight per spike and weight of 1000 seeds. These landraces must be considered as a reservoir of genes that plant breeders need in their wheat improvement programs and should be conserved both ex situ and in situ.     

Dispersal of durum wheat [<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. ssp. <Emphasis Type="Italic">turgidum</Emphasis> convar. <Emphasis Type="Italic">durum</Emphasis> (Desf.) MacKey] landraces across the Mediterranean basin assessed by AFLPs and microsatellites

A comprehensive characterization of crop germplasm is critical to the optimal improvement of the quality and productivity of crops. Genetic relationships and variability were evaluated among 63 durum wheat landraces from the Mediterranean basin using amplified fragment length polymorphisms (AFLPs) and microsatellites markers. The genetic diversity indices found were comparable to those of other crop species, with average polymorphism information content (PIC) values of 0.24 and 0.70 for AFLP and microsatellites, respectively. The mean number of alleles observed for the microsatellites loci was 9.15. Non-metric multi-dimensional scaling clustered the accessions according to their geographical origin with the landraces from the South shore of the Mediterranean Sea closely related. The results support two dispersal patterns of durum wheat in the Mediterranean basin, one through its north side and a second one through its south side.     

Genetic erosion of Ethiopian tetraploid wheat landraces in Eastern Shewa,Central Ethiopia

Ethiopia is a centre of diversity and hosts rich genetic resources of tetraploid wheats. Through time, the wheat materials were subject to genetic erosion. Closer investigation was made to assess the status of loss, and identify the possible causes by studying two districts from East Shewa. Information from primary and secondary sources was reviewed and analysed. Farmers identified 26 tetraploid wheat landraces (21 from Akaki and 17 from Ejere), which were once widely grown in the area. Of these, only six were currently available. Compared to the formerly available number of landraces, the loss of diversity in the study area was estimated to be 77%. In the Ejere locality, the loss was 100% before the launching of the on farm landrace conservation programme, and for Akaki it was 95%. Major factors that contributed to the loss include: (1) introduction and expansion of bread wheat varieties; (2) expansion of tef; (3) lack of a mechanism to re-supply seeds of tetraploid wheat landraces; (4) decline in size of landholdings; (5) changes in land use and cropping patterns; (6) lack of policy support; and (7) expansion of improved tetraploid wheat varieties. The lessons from this study underscore the importance of strengthening the local seed supply system as a prerequisite for sustaining on farm conservation of landraces. Moreover, it is necessary to initiate diversity studies focusing on the distribution and status of tetraploid wheat landraces across the country. Complementing these by molecular analyses is essential in order to assess the genetic distinctness of the landraces.     

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.     

Genetic variation of the durum wheat landrace Haurani from different agro-ecological regions

The durum wheat landrace Haurani (Triticum durum Desf.) is grown under contrasting climatic regions of Syria from Deir Ezzor, in the North-East (230 m altitude, 150 mm mean annual rainfall), to Qunaytra, in the South-West (1060 m altitude, 825 mm mean annual rainfall). In order to assess the genetic variation between and within Haurani populations, samples from eight provinces of Syria (Daraa, Damascus, Qunaytra, Deir Ezzor, Hassakeh, Aleppo, Homs and Hama) were analysed by RFLPs and seed storage proteins of glutenin subunits as markers. The analyses showed the presence of genetic polymorphisms in all populations with the highest values in those from Homs and Hassakeh. Moreover, the results point out differences in genetic distances between populations; some populations were further apart, such as Damascus and Aleppo, whereas others were closer to each other, for instance Homs and Hama. Cluster analysis identified two distinct groups of populations, characterized by geographical proximity, with similar rainfall and altitude. It is suggested that the similarity of landraces at locations close to each other might be the result of more frequent seed exchanges between farmers or of gene flow due to 5% estimated outcross rate of Haurani.     

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.     

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.     

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.     

Yield response of spring wheat cultivars (Triticum aestivum and T. turgidum) to inoculation with Azospirillum brasilense under field conditions

Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar Miriam showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar Miriam to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.     

Variation of morphological and agronomical traits, andprotein composition in durum wheat germplasm from easternEurope

Broadening the genetic base upon which the breeding of durumwheat relies is a growing concern in Italy. Exotic materials canrepresent valuable sources of adaptive features and they have beenrepeatedly exploited in the past for direct utilisation and/orintrogression by crossing into existing germplasm. An increase of theavailable genetic variation for the breeding also appearsenvisageable in terms of end-product quality. This studyassessed the variation in germplasm from eastern Europe countries,which could represent novel gene sources for durum wheat improvementin Italy, and verified the presence of variants of potential interestfor agronomical and quality characteristics to be possibly exploitedfor breeding. Fifty-nine landraces from the former USSR and 91from Bulgaria were grown in Sicily and evaluated for agronomicaltraits, spike morphological characteristics (possibly bearingsome taxonomic relevance), and protein composition at three lociencoding for glutenin subunits responsible of flour quality features.The results suggested a similar overall diversity in the two groupsconsidering either the variance of the agronomical characters, or thediversity index (H) across morphological traits, orthe frequency distribution of electrophoretic patterns of gluteninsubunits encoded at three loci. Genotypes of potential usefulness asdonors of positive agronomical or quality attributes were found inboth germplasm groups, although the agronomical characteristics ofthe exotic genotypes rarely matched those required by the breeding inthe target area. Conversely, the genetic variation found at the threeloci involved in the composition of glutenin subunits appeared ofgreater relevance for the breeding in Italy.     

Inoculation of field-grown wheat (Triticum aestivum) with Azospirillum spp. in Brazil

Summary Three field experiments with wheat were conducted in 1983, 1984, and 1985 in Terra Roxa soil in Paraná, the major Brazilian wheat-growing region, to study inoculation effects of various strains of Azospirillum brasilense and A. amazonense. In all three experiments inoculation with A. brasilense Sp 245 isolated from surface-sterilized wheat roots in Paraná produced the highest plant dry weights and highest N% in plant tops and grain. Grain yield increases with this strain were up to 31 % but were not significant. The application of 60 or 100 kg N ha^–1 to the controls increased N accumulation and produced yields less than inoculation with this strain. Another A. brasilense strain from surface-sterilized wheat roots (Sp 107st) also produced increased N assimilation at the lower N fertilizer level but reduced dry weights at the high N level, while strain Sp 7 + Cd reduced dry weights and N% in the straw at both N levels. The A. amazonense strain isolated from washed roots and a nitrate reductase negative mutant of strain Sp 245 were ineffective. Strains Sp 245 and Sp 107st showed the best establishment within roots while strain Cd established only in the soil.     

Genetic diversity of HMW glutenin subunit in Chinese common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) landraces from Hubei province

The high molecular weight (HMW) glutenin subunit composition of 111 common landraces of bread wheat collected from Hubei province, China has been determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Ninety six of the accessions were homogeneous for HMW glutenin subunit composition and 15 were heterogeneous. For the Glu-1 loci, 16 alleles were detected, 3 at the Glu-A1locus, 9 at the Glu-B1and 4 at the Glu-D1. Three novel alleles were identified, two at the Glu-B1 and one at the Glu-D1locus. Combination of these 16 alleles resulted in 14 different HMW subunit patterns. The distribution of HMW glutenin subunit alleles in a subset of 105 of the 111 accessions representing six populations was assessed both at the individual population and whole population levels. The results demonstrated that the distribution of allelic patterns varied among populations. Taken together, 62.5% of the alleles detected were considered to be rare alleles while the Glu-A1c (null), Glu-B1b (1Bx7 + 1By8) and Glu-D1a (1Dx2 + 1Dy12) alleles were found most frequently in the six populations. The subset exhibited relatively high genetic diversity (A = 5.33, P = 1.00, Ae = 1.352 and He = 0.238) with 81.5% of the diversity being within populations and 18.5% between populations.     

Effect of Developmental Stages Length on Yield and some Quality Traits of Turkish Durum Wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. Convar. <Emphasis Type="Italic">durum</Emphasis> (Desf.) Mackey) Landraces: Influence of Developmental Stages Length on Yield and Quality of Durum Wheat

The study aimed at exploring durum wheat landraces to be utilized in breeding programs. 566 single durum wheat plants selected from 117 populations collected from 12 provinces were studied. The selected material was planted for characterizing their some qualitative and quantitative traits such as percent vitreousness, pearling index, grain protein content, seed yield and thousand kernel weight; as well as determining time frame for germination-tillering, germination-shooting, germination-heading, germination-maturity, tillering-shooting (T-S), tillering-heading (T-H), tillering-maturity, shooting-heading, shooting-maturity, and heading-maturity. Mean, coefficient of variation, and confidence intervals (0.95) were computed for each of 12 provinces, for altitudinal origins with 200 m of ranges and, for each of two geographical regions separately. The highest variation existed for number of days between T-H and the lowest for number of days between T-S. The highest variation within developmental stages was observed in samples from Diyarbakir with a CV of 32.96%, from 600 to 799 altitude range with a CV of 18.86%, and from Southeast Anatolia with a CV of 20.12%.     

Genetic Diversity of Glutenin Protein Subunits Composition in Durum Wheat Landraces [Triticum turgidum ssp. turgidum Convar. durum (Desf.) MacKey] from the Mediterranean Basin

The genetic diversity of high and low molecular weight glutenin subunits of 63 durum wheat landraces from different geographical regions in the Mediterranean Basin was studied using SDS-PAGE. Great variability in glutenin composition was found, with 42 high and low molecular weight glutenin haplotypes, 20 allele combinations at the HMW-GS loci, and 18 at the LMW-GS. All five possible LMW models were detected in all Mediterranean regions. Rare alleles were found at Glu-B1 locus in high frequencies and a priori related alleles to grain quality were also observed. Global genetic diversity index was relatively high (0.67); it ranged from 0.33 to 0.66. Cluster analysis on the frequency patterns of origins grouped genotypes following a geographical structure. Rogers’ distance coefficient on frequency pattern for each region of origin showed two germplasm pools with distinct quality profiles, where South West Asian landraces were very different from the landraces of other Mediterranean areas. The relationship between different regions of origin is discussed and two possible ways of introduction of wheat in the Iberian Peninsula (N Africa and SE Europe) are hypothesized. The use of Mediterranean durum wheat landraces as source of genetic variability for grain quality improvement is highly recommended.     

Genetic diversity and intra-specific phylogeny of Triticum turgidum L. subsp. dicoccon (Schrank) Thell. revealed by RFLPs and SSRs

Today, emmer wheat, T. turgidum subsp. dicoccon, widely grown in the past is a candidate crop for sustainable agriculture in Italy. As part of a research project aimed at the enhanced use of the hulled wheat germplasm, molecular characterization was carried out to understand the genetic structure of the crop and to identify accessions of interest. A collection of 194 accessions was analyzed with 15 microsatellite loci (SSRs), while only a sample of 38 accessions was tested with 19 RFLP probes. The marker loci were selected on the basis of their independent genomic distribution. Genetic distances and allelic frequencies were calculated for each marker class. The genetic relationships were visualized with dendrograms. RFLP loci were, on average, less polymorphic than SSRs. An average Dice's genetic distance of 0.22 for RFLPs vs 0.38 for SSRs was detected, while an expected average heterozygosity per locus of 0.23 for RFLPs vs 0.26 for SSRs was also estimated. With a least number of 10 loci per marker class it was possible to identify each genotype. The most diverse accessions had different geographic origins. Germplasms from Italy and Ethiopia appear to belong to a more primitive genepool, given that a group of accessions from these countries were genetically differentiated from a Russian-Iranian group.     

Genetic diversity in populations of wild diploid wheat Triticum urartu Tum. ex. Gandil. revealed by isozyme markers

Genetic variation and its distribution within and among 23 populations of Triticum urartu collected from Syria, Lebanon, Turkey, Armenia, and Iran was estimated using isozyme markers at eight polymorphic loci. The number of alleles per locus (A= 1.21), percentage polymorphic loci (P= 20.1%), and mean gene diversity (H_e= 0.024) were relatively low. In a population from Lebanon, a high number of alleles per locus (A= 2.13) and percentage polymorphic loci (P= 87.5%) was found. On average, genetic variation among populations (G_ST= 0.407) was smaller than within-population variation (0.593). However, different patterns of genetic structure were found among various geographic regions. Interpopulation variation was highest for the Iranian populations (0.89) followed by the Turkish populations (0.66). A reverse pattern was observed for the Syrian (0.11) and for the Lebanese (0.13) populations. The Armenian populations exhibited similar interpopulation and within-population variation. Principal component and cluster analyses resulted in distinct grouping of the geographically proximal populations, with the exception of the two Iranian populations. The Turkish populations were different from the neighboring Armenian populations compared to other countries. The populations from southern Syria and those from Lebanon also exhibited a high degree of genetic diversity. The two most heterozygous loci, Mdh-2 and Pgi-2, separated the populations along the first and second principal components, respectively. Most of the rare alleles were scattered sporadically throughout the geographic regions. Rare alleles with high frequencies were found in the Turkish and Armenian populations. These results indicated that different geographic regions require specific sampling procedures in order to capture the range of genetic variation observed in T. urartu populations.