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United States Department of Agriculture

Agricultural Research Service

Title: Genetical Events Occurring During & after Triticum Turgidum Var. Durum X Dasypyrum Villosum Hybridization Recapitulate the Population Size & Time Span Required for the Transition from Tetraploid to Hexaploid Wheat Domesticati

Authors
item DE Pace, C - UNIV. VITERBO, ITALY
item Jan, Chao-Chien
item Caputi, G - UNIV. VITERBO, ITALY
item Scarascia Mugnozza, G - ACAD. NATL. SCI. ROME, IT

Submitted to: Wheat Genetics International Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2003
Publication Date: September 1, 2003
Citation: De Pace, C., Jan, C.C., Caputi, G., Scarascia Mugnozza, G.T. 2003. Genetical events occurring during and after Triticum turgidum var. durum x Dasypyrum villosum hybridization recapitulate the population size and time span required for the transition from tetraploid to hexaploid wheat domestication. Wheat Genetics International Symposium Proceedings, September 1-6, 2003, Paestum, Italy. v. 2. p. 472-474.

Interpretive Summary: Hybridization, polyploidization, and mutation played important roles for evolutionary changes and domestication for both tetraploid and hexaploid wheats and other crop species. Crossability between parental species, occurrence and frequency of viable unreduced gametes for the rise of the first fertile hybrid plant, and the time span for the appearance of important domestication-syndrome related traits in the fertile hybrid progenies are relevant data to indirectly quantify early events in wheat domestication. Because of the paucity of archaeobotanical data documenting the early stages of hexaploid wheat domestication, the experimental reconstruction of early domestication events is necessary for a recapitulation of population size and time lapse required for the transition from tetraploid to hexaploid wheat domestication. Without the nonbrittle-rachis mutation the biological transformation of the wild ancestors of maize, wheat, rice, barley and other cereal species during the first phase of domestication wouldn't have had the large impact in promoting agriculture and cereal food availability expansion it had. We use data collected during and after hybridization of two free-threshing and tough-rachis tetraploid wheat varieties with diploid hulled and brittle-rachis Dasypyrum villosum accessions, to: (a) estimate crossability, frequency of unreduced gametes in the F1 interspecific hybrid germline, and the time laps and frequency of appearance of the nonbrittle-rachis mutation after the interspecific hybridization event, and (b) infer occurrence, frequency and time line of comparable events during the transition from tetraploid to hexaploid wheat domestication. Our results support the view that the cytological (tendency of the triploid F1 plant to form unreduced gametes) and genetic changes (recessive mutations for nonbrittle rachis) for the rise of the first hexaploid wheat plant, were certainly both rapid and straightforward.

Technical Abstract: Hybridization, polyploidization, and mutation played important roles for evolutionary changes and domestication for both tetraploid and hexaploid wheats. Crossability between parental species, occurrence and frequency of viable unreduced gametes for the rise of the first fertile hybrid plant, and the time span for the appearance of important domestication-syndrome related traits in the fertile hybrid progenies, are relevant data to indirectly quantify early events in wheat domestication. Such data have been collected during and after hybridization of two free-threshing and tough-rachis tetraploid wheat varieties (Triticum turgidum var. durum cv 'Modoc' and cv 'Creso'; 2n=4x=28; AABB) with diploid hulled and brittle-rachis Dasypyrum villosum accessions (2n=2x=14; VV). Crossability was about 11%; the spikelets of the F1 had hulled glumes, unreduced gametes at the frequency of 1.24 % and 3.7 % in the male and female germ line, respectively, and wedge-disarticulation at maturity (brittle-rachis); fertile F2 progeny at the frequency of 0.046 %, derived from selfing F1 plants. A previously produced fertile F2 plant (MxV, brittle-rachis) gave a phenotypically stable 2n=6x=42, AABBVV brittle-rachis amphiploid up to the F8 when a nonbrittle-rachis mutant plant appeared at a rate of 4.4 x 10-5 per individual per generation.

Last Modified: 12/21/2014
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