Progress 11/15/00 to 11/14/04
Outputs
In order to gain an understanding of factors governing gene flow, 413 BC1 seeds obtained from 127 wheat-jointed goatgrass hybrids were evaluated for their parentage using chloroplast and nuclear microsatellite markers. The hybrids and BC1 seeds were naturally produced under field conditions. The parentage of the F1 generation was deduced from its BC1 progeny. Of the 127 hybrids evaluated, 109 (85.83%) had jointed goatgrass (F1J), while the remaining 18 F1 plants (14.17%) had wheat (F1W) as their female parent. Of the 413 BC1 plants analyzed, 358 (86.68%) had wheat (BC1W) and 24 (6.29%) had jointed goatgrass (BC1J) as the recurrent male parent. The male parentage of 31 BC1 (7.51%) plants could not be determined possiblity due to meiotically restituted gametes in their production. Aegilops cylindrica (2n=4x=28; genome CCDD) is an allotetraploid formed by hybridization between the diploid species Ae. tauschii (2n=2x=14; genome DD) and Ae. markgrafii (2n=2x=14; genome CC).
Previous research suggested that Ae. tauschii was the sole maternal parent in the formation of Ae. cylindrica. However, our analysis of an array of Ae. cylindrica accessions and its progenitors with 20 chloroplast microsatellite markers suggests that one Ae. cylindrica accession, TK 116 (PI 486249), has cytoplasm derived from Ae. markgrafii rather than Ae. tauschii. Thus, our analyses indicate that Ae. cylindrica has two types of cytoplasm originating from each of its diploid ancestors. Genetic diversity of accessions of 6 species, largely consisting of jointed goatgrass (Aegilops cylindrica; 174) were screened with 20 wheat chloroplast SSRs (Simple Sequence Repeats). The chloroplast SSR data were used to generate a tree showing genetic relatedness among the 192 accessions. Six species grouped according to their known cytoplasmic types. Two types of cytoplasm, C-type and D-type, were observed in jointed goatgrass. Plasmon types C and D were found for 86.32% and 6.89% of jointed
goatgrass accessions, respectively. The remaining 6.79% of the jointed goatgrass accessions were heterogeneous. The chloroplast SSR analysis also helped to identify key diagnostic markers, WCt-3, WCt-11 and WCt-24. These markers differentiate between plasmon types of wheat and jointed goatgrass (B, C, D and D2). These markers were used determine the female parent of the jointed goatgrass-wheat hybrids. The 192 accessions were also screened with 23 nuclear SSR markers. Genetic diversity analysis suggested low diversity in jointed goatgrass compared to its progenitors Ae. tauschii and Ae. markgrafii. Diversity of jointed goatgrass accessions collected in the USA was comparable with those collected from its native area of distribution. The accessions of Ae. cylindrica collected from native locations were interspersed with the accessions collected from USA. However, some clusters purely consisted of accessions from the USA or native locations. Among collections made in USA, a few
genotypes collected in the Pacific Northwest formed unique clusters as compared to those collected in the Great Plains, suggesting some of the accessions of Pacific Northwest may have been introduced independently.
Impacts
Results of this study will help us understand the formation of jointed goatgrass by wheat hybrids under field conditions and the role they may play in the weed problem. It is essential that we understand what is happening in the field before we can predict what may happen when herbicide-resistant wheat is introduced into the system.
Publications
- Cremieux, L., L.A. Morrison, R.S. Zemetra, and C.A. Mallory-Smith. 2001. Seed protein and chromosome number analyses of experimental wheat x jointed goatgrass (Aegilops cylindrica Host) hybrid lines. Weed Sci. Soc. Am. Abstr. p. 127.
- Gandhi, Harish T., I. Vales, C. Watson, R.S. Zemetra, C.A. Mallory-Smith, and O. Riera-Lizarazu. 2002. Investigations on the nature and source of the cytoplasm in the TK-116 accession of jointed goatgrass (Aegilops cylindrica). Proc. West. Soc. Weed Sci. p. 7.
- Zemetra, R.S., C.A. Mallory-Smith, J. Hansen, Z. Wang, J. Snyder, A. Hang, L. Kroiss, O. Riera-Lizarazu, and I. Vales. 2002. The evolution of a biological risk program: Gene flow between wheat (Triticum aestivum L.) and jointed goatgrass (Aegilops cylindrica Host). Scientific Methods Workshop: Ecological and Agronomic Consequences of Gene Flow from Transgenic Crops to Wild Relatives. 150-159.
- Morrison, L.A., O. Riera-Lizarazu, M.I. Vales, L. Cremieux, R.S. Zemetra, J. Hansen, and C.Mallory-Smith. 2002. Genetic diversity and gene flow in the crop-weed complex of wheat (Triticum aestivum L.) and jointed goatgrass (Aegilops cylindrica Host). Proc. 4th Intl. Triticeae Symp. pp. 125-130.
- Riera-Lizarazu, O., M.I. Vales, L.A. Morrison, R.Z. Zemetra, D. Morishita, J. Hansen, and C.A. Mallory-Smith. 2002. Gene flow and hybridization between wheat (Triticum aestivum) and its wild weedy relative jointed goatgrass (Aegilops cylindrica). Proc. 4th Intl. Triticeae Symp. pp. 201-205.
- Zemetra, R.S., C.A. Mallory-Smith, J. Hansen, Z. Wang, J. Snyder, A. Hang, L. Kroiss, O. Riera-Lizarazu, and I. Vales. 2002. The evolution of a biological risk program: gene flow between wheat (Triticum aestivum L.) and jointed goatgrass (Aegilops cylindrica Host). Scientific Methods Workshop: Ecological and Agronomic Consequences of Gene Flow from Transgenic Crops to Wild Relatives. OH St. Univ, Columbus, Ohio. pp. 178-187.
- Morrison, L.A., L.C. Cremieux, and C.A. Mallory-Smith. 2002. Infestations of jointed goatgrass (Aegilops cylindrica) and its hybrids with wheat (Triticum aestivum) in Oregon. Weed Sci. 50:737-747.
- Zemetra, R.S., C.A. Mallory-Smith, J.L. Hanson, Z. Wang J. Snyder, A. Hand, and L.A. Morrison. 2001. Determining the potential for gene flow between wheat and jointed goatgrass (Aegilops cylindrica). Weed Sci. Soc. Am. Abstr. p. 56.
|
Progress 01/01/03 to 12/31/03
Outputs
Screening of 192 accessions of 6 species, largely consisting of jointed goatgrass (174), with 20 wheat chloroplast SSRs (Simple Sequence Repeats) markers was completed. The chloroplast SSR data were used to generate a tree showing genetic relatedness among the 192 accessions. The tree suggests that there are two main types of cytoplasm in jointed goatgrass. The plasmon type C and plasmon type D. However, the data indicate that at the population level, plasmon type D (86.32 %) is more common than plasmon type C (6.89 %). From chloroplast SSR analysis, we could identify key diagonistic markers to help identify the maternal parent in the jointed goatgrass by wheat hybrids. The 192 accessions of the 6 species were also screened with 21 nuclear SSR markers. Our preliminary analysis suggests that more markers are needed to distinguish the taxons under study. We are currently in the process of adding extra markers. In a second study, more than 450 BC1 plants are being
analyzed to determine their parentage. Three key diagnostic chloroplast SSR markers were used to screen these BC1 plants. Our preliminary analysis suggests that 80-84% of the BC1 plants have jointed goatgrass as a female parent in the production of jointed goatgrass-wheat hybrid plants. These BC1 plants were also screened with four nuclear SSR markers. The four markers were able to identify the male parent for 76% of BC1 plants. Preliminary analysis using four nuclear markers suggests that wheat and jointed goatgrass pollinated 70% and 6% of BC1s, respectively, while parentage of the remaining 24% BC1 plants could not be determined.
Impacts
Results of this study will help us understand the formation of jointed goatgrass by wheat hybrids under field conditions and the role they may play in the weed problem. It is essential that we understand what is happening in the field before we can predict what may happen when herbicide-resistant wheat is introduced into the system.
Publications
- No publications reported this period
|