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Insect resistance. Greenbug.

Gb3 gene

Contributed by Yiqun Weng (y-weng@tamu.edu ) and Jackie C. Rudd

Background information

The greenbug, Schizaphis graminum (Rondani), affects small grain crops in different parts of the world. In the southern Great Plains of the US it is the most economically damaging aphid pest of wheat. Eleven biotypes (A to K) have been identified so far, and biotypes E, I and K currently predominate in the greenbug populations that attack wheat and sorghum. The gene Gb3 confers resistance to greenbug biotypes C, E, H, I and K (1) and was derived from Aegilops tauschii accession PI 268210 (2). Later, Gb3 was transferred into the synthetic wheat germplasm line 'Largo' (3). Gb3 was assigned to wheat chromosome 7D by cytogenetic analysis (4). Later studies used molecular marker to map Gb3 in the distal 18% of 7DL linked to several microsatellite and AFLP markers (5, 6).

Methods

Several microsatellites and AFLP markers have been found closely linked to Gb3, for more details follow to the methods section

Available germplasm

The original plant materials harboring Gb3 are Aegilops tauschii (PI 268210) and the synthetic hexaploid wheat line 'Largo' (CI 17895). TAM 110 (Gb2 + Gb3) (7) is the first wheat cultivar with resistance to prevailing greenbug biotypes. Wheat cultivars 'Above' (8), 'AP502 CL' (9) and TAM 112 (tested as TX98V9628) possess Gb3 derived from TAM 110. A set of eight near isogenic lines for Gb3 is also available (10).

References

1. Greenbug (Homoptera: Aphididae) Biotypes: selected by resistant cultivars or preadapted opportunists? Porter DR, Burd JD, Shufran KA, Webster JA, Teetes GL. In: Journal of Economic Entomology,1997, 90:1055-1065. [abstract]

2. Inheritance to resistance to greenbug toxicity in an amphiploid of Triticum turgidum/T. tauschii. Joppa LR, Timian RG, Williams ND. In: Crop Science, 1980, 20:343-344.

3. Registration of Largo, a greenbug resistant hexaploid wheat. Joppa LR, Williams ND. In: Crop Science, 1982, 22:901-902.

4. Chromosomal locations of genes for resistance to greenbug in 'Largo' and 'Amigo' wheats. Hollenhorst MM, Joppa. In: Crop Science, 1983, 23:91-93.

5. Amplified fragment length polymorphism- and simple sequence repeat-based molecular tagging and mapping of greenbug resistance gene Gb3 in wheat. Weng Y, Lazar MD. In: Plant Breeding, 2002, 121:218-223. [abstract]

6. Microsatellite markers associated with two Aegilops tauschii- derived greenbug resistance loci in wheat. Weng Y, Li W, Devkota RN, Rudd JC. In: Theoretical and Applied Genetics. In press. [abstract]

7. Registration of TAM 110. Lazar MD, Worrall WD, Peterson GL, Porter KB, Marshall DS, McDaniel ME, Nelson LR. In: Crop Science, 1997, 37:1978-1979.

8. Above winter wheat. Haley SD, Lazar MD, Quick JS, Johnson JJ, Peterson GL, Stromberger JA, Clayshulte SR, Clifford BL, Pester TA, Nissen SJ, Westra PH, Peairs FB, Rudolph JB In: Canadian Journal of Plant Science, 2003, 83: 107-108. [abstract]

9. AP502 CL winter wheat. Lazar MD, Haley SD, Quick JS, Johnson JJ, Peterson GL, Stromberger JA, Clayshulte SR, Clifford BL, Pester TA, Nissen SJ, Westra PH, Peairs FB, Rudolph JB. In: Canadian Journal of Plant Science, 2003, 83: 109-110. [abstract]

10. Registration of eight closely related wheat germplasm lines differing in biotype E greenbug resistance. Lazar MD, Worrall WD, Porter KB, Tuleen NA. In: Crop Science, 1996, 36:1419.

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