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The usefulness of a semispecific PCR system for the evaluation of genetic diversity among selected cultivars of wheat (Triticum aestivum L.) and triticale (x Triticosecale Wittm.) was investigated. A comparison was made of the diversity among cultivars of both species as revealed by primers targetting the semi-conservative sequences of the intron-exon junction. The main purpose of the study was the selection of the most informative primers from among the exon targetting (ET) and intron targetting (IT) primers of 12 to 18 bases in length. For triticale, the most satisfactory results were obtained using ET and IT primers of 18 bases in length. In wheat, complex and polymorphic banding patterns were generated by primers belonging to both groups, regardless of their length.
Kernel size and morphology influence the market value and milling yield of bread wheat (Triticum aestivum L.). The objective of this study was to identify quantitative trait loci (QTLs) controlling kernel traits in hexaploid wheat. We recorded 1000-kernel weight, kernel length, and kernel width for 185 recombinant inbred lines from the cross Rye Selection 111 × Chinese Spring grown in 2 agro-climatic regions in India for many years. Composite interval mapping (CIM) was employed for QTL detection using a linkage map with 169 simple sequence repeat (SSR) markers. For 1000-kernel weight, 10 QTLs were identified on wheat chromosomes 1A, 1D, 2B, 2D, 4B, 5B, and 6B, whereas 6 QTLs for kernel length were detected on 1A, 2B, 2D, 5A, 5B and 5D. Chromosomes 1D, 2B, 2D, 4B, 5B and 5D had 9 QTLs for kernel width. Chromosomal regions with QTLs detected consistently for multiple year-location combinations were identified for each trait. Pleiotropic QTLs were found on chromosomes 2B, 2D, 4B, and 5B. The identified genomic regions controlling wheat kernel size and shape can be targeted during further studies for their genetic dissection.
Phylogenetic relationships among wild Triticum and Aegilops species, bread wheat (Triticum aestivum) cultivars, and durum wheat (T. turgidum) cultivars were investigated using random amplified polymorphic DNA (RAPD) technique. Fourteen RAPD primers generated 328 polymorphic bands in 22 wheat species/cultivars which have the same or different genomes. DNA fragment size ranged from 290 bp to 2570 bp. In the RAPD analysis, wild Triticum and Aegilops species clustered together and were separated from all other wheat cultivars based on their genome constitution. T. monococcum and T. boeticum were closer to Aegilops species than to other wheat cultivars. T. turgidum cultivars were genetically less diverse than T. aestivum cultivars. RAPD markers specific to the D and U genomes were detected. There was a weak correlation between RAPD data and pedigree records of the cultivars sharing common ancestor(s). The results suggest that RAPD analysis can be used to distinguish wild Triticum and Aegilops species, and wheat cultivars. In addition, RAPD technique can be used to develop genome-specific markers.
In this study two sowing date in years 2007-08 (1 November as normal sowing date and 1 January as late sowing date) were used. Measurements of chlorophyll fluorescence, membrane thermo-stability, gas exchange parameters and carbohydrates content in two wheat cultivars (Dena as durum wheat and Roshan as bread wheat) at post- anthesis stage were recorded. Acquired thermo-tolerance showed significant variation in late sown conditions. It was inferred that durum wheat conferred less relative injury and greater thermo-tolerance possibly through maintaining cellular membrane integrity under high temperature stress. Data based on chlorophyll fluorescence revealed a reduction of mean value of both cultivars for Fv/Fm, in late sown conditions. There were not any significant differences in all measured traits between two experimental years. Heat stress, occurred in late sown condition, caused reduction in biological and grain yield, harvest index, number of seed per ear, ear length and grain weight of two cultivars. But these reductions in durum wheat were lower. Seed protein content of cultivars increased in late sowing date. There were significant differences between cultivars in protein content. The grain yield reduction in cv. Roshan was higher than Dena. It seemed that by increasing in fructan and glucose content, rather than starch content, durum wheat can cope on the heat stress better than bread wheat.
The present study was conducted to determine the effect of the D genome on embryoid induction and green plant regeneration in wheat anther culture and how it is influenced by low temperature and mannitol treatment. For this reason, the anther culture response of two Canadian bread wheat cultivars and their extracted tetraploids (AABB) was studied. As controls two cultivars well responding to anther-culture (i.e. cvs. Kavkaz/Cgn and Acheron) and a no-responding cultivar (cv. Vergina) were used. Approximately 3000 anthers of these cultivars were cultured and three pre-treatments were applied: cold pre-treatment for 7 and 18 days at 4°C, and 0.3M mannitol for seven days at 4°C. W14 and 190-2 were used as induction and regeneration media, respectively, and the basic MS medium as the rooting medium. No green plants were produced from the tetraploids, which supports the view that the D-genome chromosomes are necessary for androgenic response in wheat. Furthermore, the Canadian cultivars performed better after 18-day pre-treatment at 4°C. The extracted tetraploids produced fewer embryoids and performed better after seven days of cold pre-treatment. The controls well responding to anther culture performed better than the Canadian cultivars, although their best response was recorded after seven-day cold pre-treatment. Cultivar Vergina produced no green plants. The presence of mannitol influenced negatively both embryoid and green plant production. It was concluded that the D genome plays a crucial role in anther culture response of wheat and that this response is influenced by both the genotype and the duration of cold pre-treatment.
The starch and protein in wheat (Triticum aestivum L.) endosperm provide 20% of the calories eaten by humans and were heavily selected for during domestication. We examined the main storage products and gene expression patterns that may embody compositional differences between two wild species Aegilops crassa and Aegilops tauschii and cultivated bread wheat. The storage product profiles differed significantly with T. aestivum accumulating twice as much carbon as the wild species, while the latter had 1.5 to 2-fold more total nitrogen per seed. Transcriptional analyses of endosperms of similar fresh weight were compared using a cDN A macroarray. Aegilops tauschii, and especially Ae. crassa had stronger hybridizations with storage protein sequences, but while there were differences in transcripts for starch biosynthetic genes, they were less dramatic. Of these, we cloned the Starch Branching Enzymes (SBE) IIa promoter region and the genomic clone of the Brittle-1 (Bt1) ADPglucose transporter. While Ae. crassa SBEIIa sequence was more divergent than that of Ae. tauschii 's compared to bread wheat, there were no sequence polymorphisms that would explain the observed expression differences in Btl between these species. Furthermore, while there were nucleotide differences between Btl in Ae. crassa and bread wheat, they were synonymous at the amino acid level. Some of transcriptional differences identified here, however, deserve further examination as part of a strategy to manipulate wheat starch and protein composition.
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