Submitted to: Eastern Wheat Workers and Southern Small Grain Workers Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/15/1999
Publication Date: N/A
Citation: N/A Interpretive Summary: Barley yellow dwarf virus (BYDV) is the major viral pathogen of wheat and other small grain cereal crops in the world. There are no effective BYDV resistance or tolerance genes in wheat. Resistance is being achieved by integrating, into wheat, a specific 7E chromosome carrying BYDV resistance from Thinopyrum intermedium, a related wheatgrass that is completely resistant to BYDV. However, the wheatgrass chromosome adversely affects other properties of wheat such as yield, plant height and increases the time from planting to harvest. To reduce the amount of the wheatgrass DNA the wheatgrass chromosome containing lines were treated to break this 7E chromosome into smaller fragments. This approach has successfully generated wheat lines that have a significant reduction in the amount of wheatgrass DNA and are BYDV resistant. Recent evidence indicates that from these lines a further reduction in the amount of wheatgrass DNA was achieved resulting in wheat plants that are BYDV resistant and have a very small amount of the wheatgrass chromosome. These lines after further characterization will be released and will constitute the major germplasm source for BYDV resistance. To enhance the effectiveness of this resistance to subgroup I BYDV strains this same approach is being used with wheat lines containing two additional wheatgrass chromosomes. The long-term goal is to pyramid resistance genes from the three wheatgrass chromosomes to achieve a high level of resistance in wheat to all BYDV strains. The wheat lines developed in this research will be a major germplasm source for BYDV resistance. This germplasm and information will be used by national and international wheat breeding programs in public and private institutions.
Technical Abstract: In regions of the world where cereal grain crops are grown, barley yellow dwarf virus (BYDV) is the most significant viral pathogen. The absence of BYDV resistance genes in wheat has compelled breeding programs to introgress into wheat by intergeneric hybridization, resistance genes from related species. This approach resulted in the selection of a line (P29) that is resistant to BYDV and contains a chromosome from the related wheatgrass Th. intermedium. P29 is partially resistant to subgroup I and completely resistant to subgroup II BYDV strains. However, the Th. intermedium chromosome also carries agronomically unfavorable traits resulting in taller plants and a later maturity date. Molecular analyses of the progeny of the gamma-irradiated P29 seed efficiently identified BYDV susceptible and resistant translocation lines. Lines derived from one of the resistant translocation lines appear to be resistant and contain very small translocations. These lines are a significant improvement over previously identified BYDV resistant translocation lines and will be released as a major germplasm source for BYDV resistance. To supplement the partial resistance to subgroup I BYDV strains, 2700 M2 plants derived from gamma-irradiated seed of wheat containing an additional wheatgrass group 1 or group 2 chromosome were screened by ELISA to identify plants resistant to BYDV subgroup I. From this material 130 putative translocation lines are being characterized to confirm their response to BYDV infection and determine the size of the translocations. Pyramiding resistance loci derived from three wheatgrass chromosomes has the potential for achieving high levels of resistance to all BYDV strains.