RÉSUMÉ
English grain aphid (EGA, Sitobion avenae Fabricius) is an important pest in wheat (Triticum aestivum L.). To develop EGA-resistant varieties, introducing the desirable genes from related species is regarded as an efficient avenue. In this study, the F1, F2 and F3 plants derived from the cross of EGA-susceptible wheat-Psathyrostachys huashanica Keng ex Kuo amphiploid (PHW-SA, AABBDDNsNs) and EGA-resistant triticale (Zhongsi 828, AABBRR) were analyzed for EGA resistance. Consequently, PHW-SA was moderately susceptible while Zhongsi 828 and their F1 hybrids were immune, suggesting that the resistance is dominant. All the F2 plants showed high resistance or immunity over two years, indicating that EGA resistance genes are more likely carried by the rye (Secale cereale L.) chromosomes rather than the genomes A or B of Zhongsi 828. In the F3 generation, 25 of 239 lines became susceptible. Giemsa C-banding patterns revealed that these F3 lines had 38-40 chromosomes, including complete rye genome except 5R (and 2R in five lines). Genomic in situ hybridization analysis confirmed this result. During meiosis, all the chromosomes formed bivalents. Six bivalents in 20 lines and five bivalents in five lines were characterized from rye. In contrast, their F2 parental lines had 42 chromosomes (21 bivalents), containing 1R-7R of rye. No P. huashanica chromosomes were detected. Therefore, we propose that the rye chromosome 5R may be related to EGA resistance.
RÉSUMÉ
English grain aphid (EGA, Sitobion avenae Fabricius) is an important pest in wheat (Triticum aestivum L.). To develop EGA-resistant varieties, introducing the desirable genes from related species is regarded as an efficient avenue. In this study, the F1, F2 and F3 plants derived from the cross of EGA-susceptible wheat-Psathyrostachys huashanica Keng ex Kuo amphiploid (PHW-SA, AABBDDNsNs) and EGA-resistant triticale (Zhongsi 828, AABBRR) were analyzed for EGA resistance. Consequently, PHW-SA was moderately susceptible while Zhongsi 828 and their F1 hybrids were immune, suggesting that the resistance is dominant. All the F2 plants showed high resistance or immunity over two years, indicating that EGA resistance genes are more likely carried by the rye (Secale cereale L.) chromosomes rather than the genomes A or B of Zhongsi 828. In the F3 generation, 25 of 239 lines became susceptible. Giemsa C-banding patterns revealed that these F3 lines had 38-40 chromosomes, including complete rye genome except 5R (and 2R in five lines). Genomic in situ hybridization analysis confirmed this result. During meiosis, all the chromosomes formed bivalents. Six bivalents in 20 lines and five bivalents in five lines were characterized from rye. In contrast, their F2 parental lines had 42 chromosomes (21 bivalents), containing 1R-7R of rye. No P. huashanica chromosomes were detected. Therefore, we propose that the rye chromosome 5R may be related to EGA resistance.
RÉSUMÉ
The phylogenetic relationships of 15 taxa from Hystrix and the related genera Leymus (NsXm), Elymus (StH), Pseudoroegneria (St), Hordeum (H), Psathyrostachys (Ns), and Thinopyrum (E) were examined by using the Giemsa C-banded karyotype. The Hy. patula C-banding pattern was similar to those of Elymus species, whereas C-banding patterns of the other Hystrix species were similar to those of Leymus species. The results suggest high genetic diversity within Hystrix, and support treating Hy. patula as E. hystrix L., and transferring Hy. coreana, Hy. duthiei ssp. duthiei and Hy. duthiei ssp. longearistata to the genus Leymus. On comparing C-banding patterns of Elymus species with their diploid ancestors (Pseudoroegneria and Hordeum), there are indications that certain chromosomal re-arrangements had previously occurred in the St and H genomes. Furthermore, a comparison of the C-banding patterns of the Hystrix and Leymus species with the potential diploid progenitors (Psathyrostachys and Thinopyrum) suggests that Hy. coreana and some Leymus species are closely related to the Ns genome of Psathyrostachys, whereas Hy. duthiei ssp. duthiei, Hy. duthiei ssp. longearistata and some of the Leymus species have a close relationship with the E genome. The results suggest a multiple origin of the polyploid genera Hystrix and Leymus.
RÉSUMÉ
The phylogenetic relationships of 15 taxa from Hystrix and the related genera Leymus (NsXm), Elymus (StH), Pseudoroegneria (St), Hordeum (H), Psathyrostachys (Ns), and Thinopyrum (E) were examined by using the Giemsa C-banded karyotype. The Hy. patula C-banding pattern was similar to those of Elymus species, whereas C-banding patterns of the other Hystrix species were similar to those of Leymus species. The results suggest high genetic diversity within Hystrix, and support treating Hy. patula as E. hystrix L., and transferring Hy. coreana, Hy. duthiei ssp. duthiei and Hy. duthiei ssp. longearistata to the genus Leymus. On comparing C-banding patterns of Elymus species with their diploid ancestors (Pseudoroegneria and Hordeum), there are indications that certain chromosomal re-arrangements had previously occurred in the St and H genomes. Furthermore, a comparison of the C-banding patterns of the Hystrix and Leymus species with the potential diploid progenitors (Psathyrostachys and Thinopyrum) suggests that Hy. coreana and some Leymus species are closely related to the Ns genome of Psathyrostachys, whereas Hy. duthiei ssp. duthiei, Hy. duthiei ssp. longearistata and some of the Leymus species have a close relationship with the E genome. The results suggest a multiple origin of the polyploid genera Hystrix and Leymus.