Phenotypic effects of the U-genome variation in nascent synthetic hexaploids derived from interspecific crosses between durum wheat and its diploid relative Aegilops umbellulata

Moeko Okada, Asami Michikawa, Kentaro Yoshida, Kiyotaka Nagaki, Tatsuya M. Ikeda, Shigeo Takumi

Published: April 2, 2020, PLoS ONE 15(4): e0231129


Aegilops umbellulata is a wild diploid wheat species with the UU genome that is an important genetic resource for wheat breeding. To exploit new synthetic allohexaploid lines available as bridges for wheat breeding, a total of 26 synthetic hexaploid lines were generated through crossing between the durum wheat cultivar Langdon and 26 accessions of Ae.umbellulata. In nascent synthetic hexaploids with the AABBUU genome, the presence of the set of seven U-genome chromosomes was confirmed with U-genome chromosome-specific markers developed based on RNA-seq-derived data from Ae.umbellulata. The AABBUU synthetic hexaploids showed large variations in flowering- and morphology-related traits, and these large variations transmitted well from the parental Ae.umbellulata accessions. However, the variation ranges in most traits examined were reduced under the AABBUU hexaploid background compared with under the diploid parents. The AABBUU and AABBDD synthetic hexaploids were clearly discriminated by several morphological traits, and an increase of plant height and in the number of spikes and a decrease of spike length were commonly observed in the AABBUU synthetics. Thus, interspecific differences in several morphological traits between Ae.umbellulata and A.tauschii largely affected the basic plant architecture of the synthetic hexaploids. In conclusion, the AABBUU synthetic hexaploid lines produced in the present study are useful resources for the introgression of desirable genes from Ae.umbellulata to common wheat.

Fig. Genomic in situ hybridization analysis of synthetic hexaploids with the AABBUU genome.

Production and phenotypic characterization of nascent synthetic decaploids derived from interspecific crosses between a durum wheat cultivar and hexaploid Aegilops species

Shigeo Takumi, Sayaka Tanaka, Kentaro Yoshida & Tatsuya M. Ikeda

Published 27 April, 2020, Genetic Resources and Crop Evolution


Wheat and its relatives include some allopolyploid species such as Aegilops juvenalis (Thell.) Eig (DDMMUU) and Aegilops vavilovii (Zhuk.) Chenn. (DDMMSS). Here, we successfully produced for the first time three allodecaploid lines with the AABBDDMMUU and AABBDDMMSS genomes through interspecific crosses between a tetraploid wheat cultivar and the two Aegilops species. Spike architecture of the synthetic lines showing a brittle rachis phenotype strongly resembled that of the parental hexaploid Aegilops species, but not that of the parental tetraploid wheat. Phenotypic differences of the spike and spikelet morphology were caused by one of the parental Aegilops species. Glumes of the synthetic decaploids were extremely hard, and all three synthetic lines had a soft texture with a smooth starch surface in endosperm cells. The soft-textured grains of the synthetic decaploids were due to accumulation of the puroindoline proteins derived from the genomes of parental allohexaploid Aegilops species. Therefore, the nascent synthetic decaploid lines highly reflect the phenotypic characteristics of the pollen parents. With further wheat breeding, the synthetic decaploids could have great potential to improve various traits.

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