Suppression of resistance to yellow rust in synthetic hexaploid wheat
Ayele Badebo Huluka
Suppression of resistance to yellow rust in synthetic hexaploid wheat - Wageningen (Netherlands) : Wageningen Agricultural University, 1994 - 27p+appendices - Printed
Nationality: ET Thesis M S|(NL-LUW 1994 AYELE M f)
In this experiment the importance of monospore isolates was emphasized for any genetic studies. Two wild emmer accessions G342-2-2M and G148-1-2M were resistant to all six yellow rust races. Ae. squarrosa accessions, Cambridge L and Gatersleben 473 were susceptible to the applied races, while the response of Rennes 33 was varied to some of the employed races. Accession Gatersleben 143 was resistant to all six races. The spelt wheat accession, T. spelta 8 and bread wheat cv. Suwon were resistant to all but only to one Australian race, 360 El37. Suppression of resistance in SHs was observed. Suppressors are present in the three Ae. squarrosa accessions. However, evidence for the presence of suppressors in AABB genome of T. dicoccoides accession, G342-2-2M was noted. The reaction of synthetic hexaploids was varied to the type of employed races. Suppression of resistance in the majority of the synthetic hexaploids was most evident after inoculations with the Afghan races. Wherever suppression was observed it was common to notice planes with low ITs at 16 dpi and high ITs at 21 dpi. The result indicated that for this type of experiment observation days should be extended at least to 21 days. Moreover, mesothetic infection types (ITx), which are very peculiar in regular tests of common wheat with yellow rust, were frequently observed. This phenomenon is probably related to the mechanisms of suppression not discussed in this report. The effects of suppressors on already described resistance factors were pronounced in crosses between SHs and bread wheats. In a cross between SH58 and T. spelta 8, the F2 segregation ratio of Yr5 was modified to race 32EO, presumably due to a single recessive suppressor factor in Cambridge L. In a cross between cv. Suwon 92 and SH40 the inheritance of resistance factor in cv. Suwon to race 32 EO was confounded due to the presence of suppressor gene(s) in SH40. The genetics of suppressors in three Aegilops squarrosa accessions of was studied in three (reciprocal) crosses to race 7 E134b. All SHs parents and F1 population were susceptible, while the ITs in the F2 and the F3 were segregating. Based on the F2 segregation ratio a single suppressor gene was postulated in Cambridge L, and similar result was obtained in a cross between SH58 and T. spelta 8. Based on the F2 test two independent dominant suppressor genes were suspected in accessions Gatersleben 143 and Rennes 33. The F3 didn't give conclusive result because of small amount of families used. However, the segregation of ITs contributed to back up the results obtained in the F2, and are of prime importance to confirm these results in further generations in the future studies. In some crosses of SHs with bread wheat and in all crosses among SHs studied, transgression was quite common in the F2 and F3 after challenging with races virulent on both parents. The present result indicated that the observed transgression was due to suppressor genes in SHs.
English
Wheat
Hexaploidy
Rusts
Disease resistance
Gene expression regulation
Cross-breeding
Suppression of resistance to yellow rust in synthetic hexaploid wheat - Wageningen (Netherlands) : Wageningen Agricultural University, 1994 - 27p+appendices - Printed
Nationality: ET Thesis M S|(NL-LUW 1994 AYELE M f)
In this experiment the importance of monospore isolates was emphasized for any genetic studies. Two wild emmer accessions G342-2-2M and G148-1-2M were resistant to all six yellow rust races. Ae. squarrosa accessions, Cambridge L and Gatersleben 473 were susceptible to the applied races, while the response of Rennes 33 was varied to some of the employed races. Accession Gatersleben 143 was resistant to all six races. The spelt wheat accession, T. spelta 8 and bread wheat cv. Suwon were resistant to all but only to one Australian race, 360 El37. Suppression of resistance in SHs was observed. Suppressors are present in the three Ae. squarrosa accessions. However, evidence for the presence of suppressors in AABB genome of T. dicoccoides accession, G342-2-2M was noted. The reaction of synthetic hexaploids was varied to the type of employed races. Suppression of resistance in the majority of the synthetic hexaploids was most evident after inoculations with the Afghan races. Wherever suppression was observed it was common to notice planes with low ITs at 16 dpi and high ITs at 21 dpi. The result indicated that for this type of experiment observation days should be extended at least to 21 days. Moreover, mesothetic infection types (ITx), which are very peculiar in regular tests of common wheat with yellow rust, were frequently observed. This phenomenon is probably related to the mechanisms of suppression not discussed in this report. The effects of suppressors on already described resistance factors were pronounced in crosses between SHs and bread wheats. In a cross between SH58 and T. spelta 8, the F2 segregation ratio of Yr5 was modified to race 32EO, presumably due to a single recessive suppressor factor in Cambridge L. In a cross between cv. Suwon 92 and SH40 the inheritance of resistance factor in cv. Suwon to race 32 EO was confounded due to the presence of suppressor gene(s) in SH40. The genetics of suppressors in three Aegilops squarrosa accessions of was studied in three (reciprocal) crosses to race 7 E134b. All SHs parents and F1 population were susceptible, while the ITs in the F2 and the F3 were segregating. Based on the F2 segregation ratio a single suppressor gene was postulated in Cambridge L, and similar result was obtained in a cross between SH58 and T. spelta 8. Based on the F2 test two independent dominant suppressor genes were suspected in accessions Gatersleben 143 and Rennes 33. The F3 didn't give conclusive result because of small amount of families used. However, the segregation of ITs contributed to back up the results obtained in the F2, and are of prime importance to confirm these results in further generations in the future studies. In some crosses of SHs with bread wheat and in all crosses among SHs studied, transgression was quite common in the F2 and F3 after challenging with races virulent on both parents. The present result indicated that the observed transgression was due to suppressor genes in SHs.
English
Wheat
Hexaploidy
Rusts
Disease resistance
Gene expression regulation
Cross-breeding