Intraspecific chromosomal polymorphism ofTriticum araraticum (Poaceae) detected by C-banding technique

DifferentTriticum araraticum lines were studied by C-banding method. The intraspecific divergence ofT. araraticum was shown to be caused mainly by large chromosomal rearrangements. Two main chromosomal types were distinguished among the studied lines: (1) a karyotype similar to that ofT. timopheevii and (2) different one. The first type includes some lines ofT. araraticum subspp.kurdistanicum andararaticum; the second comprises most lines ofT. araraticum subsp.araraticum. The lines of the first type can give fertile F₁ hybrids withT. timopheevii.     

Comparison of the chromosomes of Triticum timopheevi with related wheats using the techniques of C-banding and in situ hybridization

Summary The chromosomes of the tetraploid wheats Triticum timopheevi (Genome AAGG) and T. araraticum (Genome AAGG) were C-banded at mitosis. The identity of the banded and unbanded chromosomes was then established by firstly making comparisons with the hexaploid species T. zhukovskyi which has the genome formula AAAAGG. Secondly, the meiotic pairing in F₁ hybrids between T. timopheevi and diploid wheats was examined by means of C-banding. The results showed that the banded chromosomes belonged to the G genome, while the unbanded chromosomes belonged to the A genome. Only one of the two pairs of satellited chromosomes had strong heterochromatic bands. The relationship between the genomes of T. timopheevi and T. dicoccum (Genome AABB) was then assessed at meiosis in hybrids between these species, using the techniques of C-banding and in situ hybridisation of a cloned ribosomal RNA gene probe. It was concluded that there were differences both in the amount and distribution of heterochromatin and also translocation differences between the species.     

Occurrence of fungal endophytes in cultivars ofTriticum aestivum in South Africa

Fungal endophytes were isolated from leaves, roots and stems of four wheat cultivars and a breeding line at three different sampling dates during the 1993 growing season. Of the 55 different fungal taxa encountered, 19 were present at relative importance values of more than 5%. No cultivar-related differences in the assembleges of endophytes were observed.Phoma glomerata was not restricted to only one tissue type, whereasAlternaria alternata, basidiomycete sp. 1,Pleospora herbarum andEpicoccum nigrum occurred primarily in the leaves, andFusarium avenaceum was extremely frequent in roots. In general, colonization by endophytes increased with the age of the plants. Most endophytes were isolated from wheat leaves. Successional colonization of a given tissue type was quantitative rather than qualitative, with a given fungal taxon increasing or decreasing over the period sampled, rather than replacing the fungi initially encountered.Present address: Téra d'Sott 5, CH-6949, Comano, Switzerland.     

Increased NaCl-tolerance in wheat (Triticum aestivum L. andT. durum desf.) through in vitro selection

Summary Callus cultures were initiated from immature embryos of oneTriticum aestivum and threeT. durum cultivars. Growing morphogenic calli were exposed to different concentrations of NaCl (0, 0.3, 0.5, and 0.7%) added to the culture medium during two subsequent subcultures (4 wk each). The growth rate of the calli was determined by the relative fresh weight callus growth (RFWCG). The callus growth of all investigated genotypes was slightly changed in the presence of 0.3 and 0.5% NaCl, but strongly inhibited by 0.7% NaCl. Selected NaCl-tolerant clones were isolated and plants were regenerated on MS-based regeneration medium without NaCl. The regeneration capacity of the selected calli was highly reduced compared to the control. The highest number of regenerants was scored for cv. Gladiator (T. aestivum). All regenerated plants were morphologically normal and many developed to maturity and set seeds. Seedlings from the R₁ generation of selected and control plants were treated with 0.5% NaCl in vivo in liquid cultures for 6 wk. Salt tolerance of the progenies of selected plants appeared in all cultivars, but those derived from calli grown on medium with 0.7% NaCl showed the highest survival rate.T. aestivum showed higher tolerance to NaCl salinity thanT. durum.     

Pathogenic and non-pathogenic mycoflora in the air and phylloplane ofTriticum aestivum L.

Aerobiological investigations were carried out over wheat (Triticum aestivum L.) fields near Barrackpore, West Bengal, India for two consecutive crop seasons. In 1990–91, except for the very seedling stage there was a more or less uniform spore count up to the maximum vegetative growth state and from flowering onwards, a gradual increase in total cfus was observed with the peak (331 CFUs) during the harvesting stage. In the second season, similar results were recorded where peak spore load (2064 CFUs) in the air was during harvesting operation followed by a sudden decline in the empty field.Cladosporium spp. dominated both the seasons mainly up to February.Penicillium, Curvularia, Aspergillus andCephalosporium were the most frequent non-pathogenic fungal types. Among the pathogenic fungi,Alternaria andDrechslera were recorded to be the most virulent to wheat crop, after inflorescence to later stages in both the seasons causing heavy leaf damage producing necrotic spots during which peak cfus were found.Fusarium was frequently found showing the peak during vegetative growth period.Sclerotium was more common in the second season than in the first season. High occurrence ofnigrospora was recorded in the earlier stages. Sterile forms' were found regularly. The phylloplane studies revealed thatCladosporium was the most dominant flora contributing 40–66% up to February in winter; gradually disappeared from the leaf surface with the onset of summer.Aspergillus andPenicillium showed the reverse picture. WhileCurvularia was isolated in high amount during later stages;Nigrospora mainly during the vegetative growth stages.Alternaria (caused Alternaria blight) andDrechslera were significantly isolated during harvesting (28.08%)and at late ‘grain maturation’ stage (80.10%), respectively.Sclerotium and ‘Sterile forms’ were recorded regularly unlikeFusarium andHelminthosporium.     

The configuration of the seminal roots ofTriticum aestivum L. (Poaceae)

The seminal root system of wheat (Triticum aestivum L.) is composed of the primary seminal root, the first pair of seminal roots, and the second pair of seminal roots, which are known to grow in different directions. The direction of root growth, which can be expressed by ϑ (the angle between the root and the plumb line) and φ (the angle between the root and a vertical plane including the primary seminal root), was studied with special attention to the latter. It was measured on seedlings grown in a small hemispherical soil-filled mesh basket. There were varietal differences in the φ of the first pair of roots (φ_f) and in the φ of the second pair of roots (φ_s). (φ_f) and (φ_s) were significantly correlated. The mean distance (MD), a measure to evaluate the efficiency of root spacing, was correlated with the difference between (φ_f) and (φ_s). Neither experimentally applied low soil water potential nor the excision of the primary seminal root affected φ. When the grain was sown vertically with the tip of the embryo pointing downwards, it was found that the growth movement into a direction different from the plumb line and (φ_s) was greatly modified. it is suggested that certain internal mechanisms, possibly involving gravitropic reactions, are operating to control the direction of root growth. The significance of root growth direction at the seedling stage is discussed.     

Silica content ofTriticum aestivum L. in relation to humic acid concentrations in the soil

Summary The weathering of soil minerals by humic acids is linked with increased silica content of wheat plants.     

Identification of Haynaldia villosa chromosomes added to wheat using a sequential C-banding and genomic in situ hybridization technique

Genomic in situ hybridization (GISH) offers a convenient and effective method for cytological detection, but can not determine the identity of the chromosomes involved. We integrated C-banding with GISH to identify Haynaldia villosa chromosomes in a wheat background. All chromosomes of H. villosa showed C-bands, either in telomeric regions or in both telomeric and centromeric regions, which allowed unequivocal identification of each H. villosa chromosome. The seven pairs of H. villosa chromosomes were differentiated as 1–7 according to their characteristic C-bands. Using a sequential C-banding and GISH technique, we have analyzed somatic cells of F₃ plants from the amphiploid Triticum aestivum-H. villosa x Yangmai 158 hybrids. Three plants (94009/5-4,94009/5-8 and 94009/5-9) were shown to contain H. villosa chromosome(s). 94009/5-4 (2n = 45) had three H. villosa chromosomes (2, 3 and 4); 94009/5-8 (2n = 45) possessed one chromosome 4 and a pair of chromosome 5, and 94009/5-9 (2n = 43) was found to have one chromosome 6 of H. villosa. The combination of GISH with C-banding described here provides a direct comparison of the cytological and molecular landmarks. Such a technique is particularly useful for identifying and localizing alien chromatin and DNA sequences in plants.     

Cytogenetic investigation of Triticum timopheevii (Zhuk.) Zhuk. and related species using the C-banding technique

Triticum timopheevii and related species T. militinae (2n=28, A^tG) and T. zhukovskyi (2n=42, A^mA^tG), hybrids T. kiharae, T. miguschovae, the amphidiploid T. timopheevii x T. tauschii (all 2n=42, A^tGD), T. fungicidum (ABA^tG) and T. timonovum (2n=56, A^tA^tGG) were analyzed using the C-banding technique. Chromosomes of the A^m and A^t genomes in the karyotype of T. zhukovskyi differed in their C-banding pattern. Partial substitutions of A^t-genome chromosomes and a complete substitution of the G-genome chromosomes by homoeologous chromosomes of an unidentified tetraploid wheat species with an AB genome composition were found in the T. timonovum karyotype. A^t- and G-genome chromosomes in the karyotypes of all studied species had similar C-banding patterns and were characterized by a low level of polymorphism. The comparative stability of the A^t and G genomes is determined by the origin and specifity of cultivation of studied species.     

Pathogenic and non-pathogenic mycoflora in the air and phylloplane ofTriticum aestivum L

Aerobiological investigations were carried out over wheat (Triticum aestivum L.) fields near Barrackpore, West Bengal, India for two consecutive crop seasons. In 1990–91, except for the very seedling stage there was a more or less uniform spore count up to the maximum vegetative growth stage and from flowering onwards, a gradual increase in total cfus was observed with the peak (331 CFUs) during the harvesting stage. In the second season, similar results were recorded where peak spore load (2064 CFUs) in the air was during harvesting operation followed by a sudden decline in the empty field.Cladosporium spp. dominated both the seasons mainly up to February.Penicillium, Curvularia, Aspergillus andCephalosporium were the most frequent non-pathogenic fungal types. Among the pathogenic fungi,Alternaria andDrechslera were recorded to be the most virulent to wheat crop, after inflorescence to later stages in both the seasons causing heavy leaf damage producing necrotic spots during which peak cfus were found.Fusarium was frequently found showing the peak during vegetative growth period.Sclerotium was more common in the second season than in the first season. High occurrence ofNigrospora was recorded in the earlier stages. Sterile forms were found regularly. The phylloplane studies revealed thatCladosporium was the most dominant flora contributing 40–66% up to February in winter; gradually disappeared from the leaf surface with the onset of summer.Aspergillus andPenicillium showed the reverse picture. WhileCurvularia was isolated in high amount during later stages;Nigrospora mainly during the vegetative growth stages.Alternaria (caused Alternaria blight) andDrechslera were significantly isolated during harvesting (28.08%) and at late grain maturation stage (80.10%), respectively.Sclerotium and Sterile forms were recorded regularly unlikeFusarium andHelminthosporium.     

Detection of 5S rDNA and other repeated DNA on supernumerary B chromosomes ofTriticum species (Poaceae)

The supernumerary B chromosomes ofTriticum speltoides andT. tripsacoides were analyzed in mitotic metaphases of spike primordium cells by C-banding and in situ hybridization (ISH) analyzes. B chromosomes ofT. speltoides have larger telomeric and interstitial C-bands, whereas those ofT. tripsacoides are almost completely devoid of C-bands. A prominent ISH site of rye related DNA sequences (using probe pSc119) was detected on B chromosomes ofT. tripsacoides and only a minor ISH site was observed on theT. speltoides B chromosomes. However, two ISH sites of 5S rRNA loci were detected at a terminal and an interstitial location of theT. speltoides B chromosomes. These sites were absent on B chromosomes ofT. tripsacoides. The results are discussed with respect to the phylogenetic origin of these B chromosomes.     

Inter- and intraplant C-banding polymorphism in one population ofAegilops comosa subsp.comosa var.comosa (Poaceae)

The Giemsa C-banding pattern of the chromosomes of the native self-pollinatedAegilops comosa subsp.comosa var.comosa was studied. Six of the seven chromosomes of the haploid genome were found to be polymorphic for C-banding patterns. Chromosome A had four variants, chromosome E three variants and each of the chromosomes B, D, and F two variants. Chromosomes E and G were polymorphic for arm length and arm ratio.This paper is part of the doctoral dissertation ofA. Georgiou.     

An unusual feature of developing protophloem sieve elements in roots ofTriticum aestivum L.

Summary Developing protophloem sieve elements in roots of wheat are arranged in single vertical files. In the last immature differentiating sieve element bearing ribosomes the proximal end of the cytoplasm displays a diluted appearance in contrast to the distal end where the cytoplasm exhibits a considerably increased electron density. Differences can also be observed in ribosome quantity, organelle ultrastructure and the time of initiation of cell component degradation, those at the proximal end disorganizing first, suggesting a nonsimultaneous disorganization of the cell components in the two areas. This phenomenon, termedheterochronic lysis, is presumably an expression of an existing polarity not detectable in younger stages, but it might also be the result of an asynchronous enzymatic activity.Abbreviations CW Cell wall - D dictyosome - ER endoplasmic reticulum - M mitochondrion - N nucleus - P plastid - SE sieve element - SP sieve plate     

Cultivar identification in T. aestivum using highly polymorphic RFLP probes

Two probes, specific for HMW-glutenins and -gliadins have been used to identify 50 common wheat Italian cultivars, most of which are closely related, and four common wheat cultivars originating outside Italy. The probes revealed complex polymorphic patterns; three probe/enzyme combinations had the necessary sensitivity for the identification of all 54 cultivars. As already shown for potato and barley, the use of four-cutter restriction enzymes and polyacrylamide gels proved particularly useful for detecting polymorphism.     

Identification of C-banded chromosomes in meiosis of common wheat,Triticum aestivum L.

Summary The C-banding pattern of nine meiotic chromosomes of common wheat (Triticum aestivum L.) as described. In F₁s of crosses between monosomics of Chinese Spring and two Spanish wheat cultivars, univalent chromosomes were used to aid the recognition and analysis of the C-banding pattern for the individual chromosomes. The identification of one chromosome involved in one translocation in Chinese Spring x Pané 247 has been made through heterochromatin bands observed in the chromosomes involved in multivalents.     

Cytological identification of the genomes in pentaploidAllium neapolitanum using Giemsa C-banding

Two homoeologous sets of chromosomes in pentaploidAllium neapolitanum Cyr. (Liliaceae) are recognizable by their C-bands. The banding pattern is the same for one Californian and five Yugoslavian populations, suggesting a common chromosomal origin. Predominant meiotic association of identically banded homologues indicates a genomic formula of AA A_I BB, confirms an allopolyploid origin, and argues against genetically controlled pairing.     

Inferred chromosome morphology of the ancestral genome ofTriticum

The lengths of the A, B, and D genomes of common wheat,Triticum aestivum, were measured from the karyotype. Relative to the B genome, standardized as length 1.000, the lengths of the A and D genomes were 0.835 and 0.722, respectively. The lengths of the chromosome arms in the A and D genomes were then multiplied by the appropriate constants so that the total lengths of each genome also equalled 1.000. These calculations revealed that homoeologous chromosomes in wheat, with a few exceptions, have similar sizes and arm ratios. The arm lengths of the three homoeologues in each homoeologous group were then averaged. These average chromosomes turned out to be remarkably similar, in size and arm ratio, to their homoeologues in the E genome ofElytrigia elongata. This evidence and data on cross-compatibility and morphological characteristics suggested that the genusTriticum is a result of adaptive radiation from the perennial genusElytrigia, specifically from the complex of species possessing the E genome or one closely related to it.     

Karyotype and C-banding inTrigonella sectionFoenumgraecum (Fabaceae)

The six species of the sectionFoenum-graecum ofTrigonella have the same chromosome number, 2n = 16.T. gladiata andT. cariensis have fairly symmetrical karyotypes, while those ofT. foenum-graecum, T. berythea, T. macrorrhyncha andT. cassia are asymmetrical. C-bands are present in all six species but the number of bands and their positive vary considerably among the species. The karyotype evidence suggests that none of the available species of theFoenum-graecum section can be considered as the wild progenitor of fenugreek.     

The chromosomal location of factors determining the presence of phenolic compounds in wheat (Triticum aestivum L.)

Summary Using thin-layer chromatography and nulli-tetrasomic and ditellosomic series of Triticum aestivum L. cv. Chinese Spring, it has been possible to relate the phenolic compounds found in adult plant leaves and 12 day-old seedling leaves with the chromosomes or chromosome arms 1 B, 2 BL, 3 BL, 5 A, 6 AL, 7 B and 7 DS.     

Genome relationship betweenPsathyrostachys huashanica andP. fragilis (Poaceae)

Hybrids between the Chinese endemic speciesPsathyrostachys huashanica Keng and the SW. Asian speciesP. fragilis (Boiss.)Nevski (all 2n = 14) developed normally but were completely sterile. Meiotic analyses revealed a high chiasma frequency indicating that the two species as well asP. juncea (Fisch.)Nevski share the same basic genome (called N). The hybrid nature of the plants was established through karyotype analysis and Giemsa C-banding.