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REGISTRATIONS OF GERMPLASM

Registration of Six Germplasms of Bread Wheat having Variations of Cytogenetically Engineered Wheat–Rye Translocation 1RS.1BL

Department of Botany and Plant Sciences, University of California, Riverside CA 92521-0124

^* Corresponding author (ajoel{at}ucrac1.ucr.edu)

Six wheat (Triticum aestivum L.) germplasms were developed by cytogenetic chromosome engineering to remedy the bread making quality defect associated with the presence of the wheat–rye centric translocation 1RS.1BL (UCRBW01-1, Reg. no. GP-732, PI 628644; UCRBW01-2, Reg. no. GP-733, PI 628645; UCRBW01-3, Reg. no. GP-734, PI 628646; UCRBW01-4, Reg. no. GP-735, PI 628647; UCRBW01-5, Reg. no. GP-736, PI 628648; UCRBW01-6, Reg. no. GP-737, PI 628649). Translocation 1RS.1BL is known to improve agronomic performance of wheat in some genetic backgrounds (Rajaram et al., 1983), but can reduce bread making quality (Zeller et al., 1982). The quality defect results from the removal of several seed storage protein loci normally located on wheat chromosome arm 1BS and from the introduction of the Sec-1 locus encoding rye secalins, on rye (Secale cereale L.) arm 1RS. The original translocation 1RS.1BL was from ‘Genaro T 81’, from the International Maize and Wheat Improvement Center (CIMMYT). All cytogenetic manipulations were performed in ‘Pavon F 76’. The pedigree of all six germplasms is Genaro T 81/7*Pavon F 76//Pavon ph1b/3/4*Pavon F 76 where Pavon ph1b is Chinese Spring ph1b/8*Pavon Mono 5B.

The strategy of Sears (1981) was followed to produce the intercalary introgressions. The rye arm 1RS in the original translocation 1RS.1BL was induced to recombine with wheat chromosome arm 1BS by the absence of the Ph1 locus (ph1b mutation); primary (single breakpoint) 1BS-1RS recombinant chromosomes were selected and their breakpoints genetically mapped. Primary recombinants with breakpoints in the appropriate positions were intercrossed and secondary recombinant chromosomes (with intercalary introgressions) were selected; these were again intercrossed to produce tertiary recombinant 1RS arms with double introgressions from 1BS (Lukaszewski, 2000).

Chromosomes MA1 (UCRBW01-1) and MA2 (UCRBW01-2) are tertiary recombinant wheat–rye translocation chromosomes T1RS.1BS.1BL, each with two intercalary segments from wheat chromosome arm 1BS introgressed into rye arm 1RS. The distal wheat segment in both chromosomes is identical and it is 1.4 centomorgans (cM) in length. It contains storage protein loci Gli-B1 and Glu-B3 from wheat 1BS into rye 1RS. The proximal wheat inserts in these chromosomes are about 1to 2 cM in length and differ by the positions of their proximal breakpoints. It is believed that the proximal wheat segment in MA1 is shorter than that in MA2, but with very low crossover frequencies in both segments, solid evidence to support this belief is lacking. These proximal wheat inserts remove from the rye arm the segment that in a normal chromosome carries locus Sec-1. The distal and proximal wheat inserts in chromosomes MA1 and MA2 are separated by a rye segment of the same length in both chromosomes that carries disease resistance loci Pm8, Yr9, Lr26, and Sr31. Because of their complicated structure, chromosomes MA1 and MA2 may disassemble by crossing over with normal chromosome arms 1BS or 1RS. These crossover frequencies with 1BS were about 4.4% and with 1RS, 3.2% (Lukaszewski, 2001).

Chromosomes Te1 (UCRBW01-3) and Te2 (UCRBW01-4) are tertiary recombinant wheat–rye translocation chromosomes T1RS.1BS.1BL, each with two segments from wheat chromosome arm 1BS introgressed into 1RS. They differ from chromosomes MA1 and MA2 by the absence of the terminal rye segment: the distal wheat segment in both chromosomes stretches to the telomere. Because of this difference in structure, chromosomes Te recombine more frequently than MA with normal chromosomes 1B (about 18%). Most of this difference comes from crossover events in the terminal wheat segment. Such crossovers do not affect the structure of the chromosomes but may change their allelic constitution at the Gli-B1 and Glu-B3 loci (Lukaszewski, 2001).

Chromosomes 1BS_44:21.1BL (UCRBW01-5) and 1BS_38:9.1BL (UCRBW01-6) are wheat chromosomes 1BS with intercalary inserts of rye chromatin from the 1RS.1BL translocation. In both chromosomes, the rye segments carry disease resistance loci Pm8, Yr9, Lr26, and Sr31. Judging from the map positions of the translocation breakpoints used in the creation of these two chromosomes, as determined by several genetic mapping tests, the rye insert in 1BS_44::21.1BL is shorter than that in 1BS_38:9.1BL.

The engineered chromosomes restore bread wheat-like composition of the storage protein loci. Therefore, it is believed that the bread making quality of the translocation lines is normal while maintaining the agronomic benefits associated with the presence of the 1RS.1BL translocation. Preliminary SDS-sedimentation tests of MA1 and MA2 lines did not reveal any reduction relative to original Pavon but the yield potential of these lines has not yet been tested.

Small quantities of seed of these lines can be obtained for research and breeding purposes from the author. In addition to the Pavon stocks listed above, MA1 can be obtained as translocation homozygote following two and three backcrosses to ‘Culver’ hard red winter wheat, and following three backcrosses to ‘Bonus’ hard red spring wheat.

NOTES

Registration by CSSA.

Accepted for publication October 31, 2002.

REFERENCES

• Lukaszewski, A.J. 2000. Manipulation of the 1RS.1BL translocation by induced homoeologous recombination. Crop Sci. 40:216–225.[Abstract/Free Full Text]
• Lukaszewski, A.J. 2001. Breeding behavior of the cytogenetically engineered wheat-rye translocation chromosomes 1RS.1BL. Crop Sci. 41:1062–1065.[Abstract/Free Full Text]
• Rajaram, S., C.E. Mann, G. Ortiz-Ferrara, and A. Mujeeb-Kazi. 1983. Adaptation, stability and yield potential of certain 1B/1R CIMMYT wheats. p. 613–621. In S. Sakamoto (ed.). Proc. Intl. Wheat Genet. Symp., 6th, Kyoto, Japan. 28 Nov.–3 Dec. 1983. Plant Germplasm Intl. Kyoto Univ. Kyoto, Japan.
• Sears, E.R. 1981. Transfer of alien genetic material to wheat. p. 75–89. In Wheat science- Today and tomorrow. Cambridge University Press, Cambridge, England.
• Zeller, F.J., G. Gunzel, G. Fischbeck, P. Gerstenkorn, and D. Weipert. 1982. Veranderung der Backeigenschaften der Weizen-Roggen-Chromosomen-Translokation 1B/1R. Getreide Mehl Brot. 36:141–143.

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