Location: Cereal Crops Research2010 Annual Report
1a. Objectives (from AD-416)
Fusarium head blight (FHB) or scab,caused by the fungus Fusarium graminearum Schwabe, is a serious disease of wheat. The research objective is to develop genetic resistance to FHB in durum, or macaroni, wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) by exploiting novel sources of resistance in the wild relatives. It has been difficult to identify effective sources of resistance in durum wheat cultivars. However, several wild grasses, including diploid wheatgrasses in the secondary or tertiary gene pool of wheat, are excellent sources of FHB resistance that may be incorporated into durum germplasm. Improved durum germplasm with reliable FHB resistance could then be used to incorporate resistance genes into durum and bread wheat cultivars. Specific subobjectives of this project are to: a. Develop alien addition lines involving chromosomes or chromatin, with FHB resistance from diploid wheatgrasses, Lophopyrum elongatum (Host) Á. Löve [= Agropyron elongatum (Host) Beauv.] and Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (= Agropyron bessarabicum Savul. & Rayss). b. Initiate new crosses with other potential donors such as Thinopyrum junceiforme (Löve & Löve) Löve, 2n = 4x = 28; J1J1J2J2 genomes) and Thinopyrum nodosum [= Lophopyrum nodosum (Nevski) Á. Löve] that may provide new sources of alien chromosomes with FHB resistance. c. Characterize the added alien chromosome(s) from the wild relatives that confer FHB resistance to durum wheat. d. Evaluate both FHB resistance and mycotoxin deoxynivalenol (DON) accumulation with the longer-term objective of releasing FHB-resistant germplasm. e. Assess the genomic relationships between wheat and related species in the intergeneric hybrids.
1b. Approach (from AD-416)
Alien gene transfer into durum wheat will be carried out by tools of classical and molecular cytogenetics. The cytogenetic techniques will involve sexual hybridization between durum cultivars and wild grasses,coupled with induction of pairing among chromosomes of parental species by manipulation of the pairing-control mechanism(Ph1). This approach will facilitate transfer of alien chromatin into the durum genome, which will then be characterized using fluorescent genomic in situ hybridization (fl-GISH) and chromosome-specific markers. Using this approach, alien addition lines involving diploid wheatgrass (Lophopyrum elongatum and Thinopyrum bessarabicum) chromosomes or chromatin with FHB resistance will be developed. In addition to using these two diploid wheatgrasses as donors of FHB resistance, we will initiate new crosses with other potential donors such as Thinopyrum junceiforme and Thinopyrum nodosum (= Lophopyrum nodosum) that may provide new sources of alien chromosomes with resistance. Fertile hybrid derivatives and stable alien addition lines will be screened for FHB resistance using the techniques we have already standardized.
3. Progress Report
Fusarium head blight (FHB) is a serious disease of cultivated wheats. Current durum cultivars have little or no FHB resistance. By transferring chromosome 1E from Lophopyrum elongatum into durum cultivar Langdon, we previously produced a stable durum alien disomic addition line, DGE-1. To produce a resistant durum cultivar it would be desirable to transfer resistance genes from 1E into the durum chromosome complement. Homoeologous group-1 chromosomes 1A or 1B of durum would be the logical chromosomes for such an exchange to occur. Therefore, we crossed DGE-1 with Langdon disomic substitution lines, Langdon 1D(1A) and Langdon 1D(1B) and produced F2 plants segregating for 1A, 1B, 1D, or 1E and any combination thereof. We have also developed stable durum disomic addition lines involving Thinopyrum bessarabicum chromosomes 1J, 5J, 6J, and 7J. We have produced 12 hybrids derived by crossing durum, cultivars and substitution lines with Thinopyrum nodosum with and without Ph1. Chromosome pairing data have been collected and further studies are in progress. Fertile BC1 and later generations will be developed for FHB screening. To identify the individual chromosomes 1A, 1B, 1D or 1E and any possible chromosome interchanges in segregating plants from crosses of DGE-1, we screened several molecular markers and selected the most suitable ones. We used fluorescent genomic in situ hybridization as an adjunct tool for chromosome identification. Molecular markers were selected to identify Th. bessarabicum chromosomes in durum disomic addition lines. To induce homoeologous pairing between the alien chromosome 1E and durum chromosomes 1A or 1B, we made crosses between DGE-1 and Cappelli mutant ph1cph1c. Chromosome pairing was scored in the segregating F2 generation which would be the first generation with or without the Ph1 gene. Segregation for the Ph1 gene and chromosome 1E is being studied, using molecular markers. Xpsr128 and Xpsr574 are being used to determine the presence of Ph1 and Xedm74 and Xedm17 to ascertain the presence of chromosome 1E.