Origin Of Hexaploid Research Articles

Genetic variability of spelt factor gene in Triticum and Aegilops species

BackgroundThreshability, rachis fragility and spike shape are critical traits for the domestication and evolution of wheat, determining the crop yield and efficiency of the harvest. Spelt factor gene Q controls a wide range of domestication-related traits in polyploid wheats, including those mentioned above. The main goal of the present study was to characterise the Q gene for uninvestigated accessions of wheats, including four endemics, and Aegilops accessions, and to analyze the species evolution based on differences in Q gene sequences.ResultsWe have studied the spike morphology for 15 accessions of wheat species, including four endemics, namely Triticum macha, T. tibetanum, T. aestivum ssp. petropavlovskyi and T. spelta ssp. yunnanense, and 24 Aegilops accessions, which are donors of B and D genomes for polyploid wheat. The Q-5A, q-5D and q-5S genes were investigated, and a novel allele of the Q-5A gene was found in accessions of T. tibetanum (KU510 and KU515). This allele was similar to the Q allele of T. aestivum cv. Chinese Spring but had an insertion 161 bp in length within exon 5. This insertion led to a frameshift and premature stop codon formation. Thus, the T. tibetanum have spelt spikes, which is probably determined by the gene Tg, rather than Q. We determined the variability within the q-5D genes among hexaploid wheat and their D genome donor Aegilops tauschii. Moreover, we studied the accessions C21–5129, KU-2074, and K-1100 of Ae. tauschii ssp. strangulata, which could be involved in the origin of hexaploid wheats.ConclusionsThe variability and phylogenetic relationships of the Q gene sequences studied allowed us to clarify the relationships between species of the genus Triticum and to predict the donor of the D genome among the Ae. tauschii accessions. Ae. tauschii ssp. strangulata accessions C21–5129, KU-2074 and K-1100 are the most interesting among the analysed accessions, since their partial sequence of q-5D is identical to the q-5D of T. aestivum cv. Chinese Spring. This result indicates that the donor is Ae. tauschii ssp. strangulata but not Ae. tauschii ssp. tauschii. Our analysis allowed us to clarify the phylogenetic relationships in the genus Triticum.

Formation and establishment of neopolyploids from sterile hybrids in Drosera in a disturbed environment

Neopolyploid species have been used as model plants to elucidate the consequences of hybridization and polyploidy. Two Drosera species, D. anglica Hudson (2n = 4x = 40) and D. rotundifolia L. (2n = 2x = 20), and the hybrid D. ×obovata Mert. et Koch (2n = 3x = 30), which results from their crossing, have been reported from Hokkaido Island, northern Japan. Recently, we discovered unexpected higher ploidy levels within the population of these Drosera from a post-mined peatland, in Sarobetsu mire of Hokkaido. The ploidy levels were determined by flow cytometry. Polyploids were tagged and monitored at the site for three years. The morphological characteristics of the neopolyploid leaves and flowers were determined and compared to D. anglica, D. rotundifolia and D. ×obovata. Seeds collected from hexaploids were incubated in a laboratory to verify their viability. Hexaploids occurred in the field over the three years of monitoring and produced a few flowers and viable seeds; however, octoploids were extinct in the second year. The leaf shape quantified by the blade length to blade width ratio showed that the ratios of hexaploids were intermediate between D. ×obovata and D. rotundifolia, suggesting that the origin of hexaploids was likely to originate from the triploid D. ×obovata. Polyploidy may occur in disturbed habitats more commonly than previously thought.

Speciation in Chenopodium in West Bengal, India

Two diploid cytotypes of Chenopodiumalbum have earlier been proposed as the probable ancestors ofhexaploid C. album in Gangetic Plainof West Bengal on the basis of cytomorphological data. The present study withthe diploid cytotypes of C. album (onebroad leaved, another narrow leaved), one wild species, C.murale and the hexaploid C.album utilizing parameters like seed protein, isozyme,RAPD, tissue culture along with conventional cytomorphological data supports ourearlier hypothesis of allopolyploid origin of hexaploid C.album. The results indicate that all the three diploidprogenitors have contributed for the evolution of present day semi-cultivatedhexaploid C. album. This study furthersuggests that the diploid cytotypes had been evolved sympatrically.