2011 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.
Current durum cultivars do not have resistance to Fusarium Head Blight (FHB), a serious disease of cereals. We found earlier that a diploid wheatgrass (Lophopyrum elongatum) is highly resistant to this ravaging disease. A durum disomic addition line was produced by incorporating two doses of chromosome 1E of this wheatgrass, making the addition line more tolerant to the disease. We have since been attempting to transfer resistance from the added chromosome 1E into the homoeologous group-1 chromosomes of durum. In the course of these studies we have produced disomic alien substitution lines in which chromosome 1A and 1B of durum, respectively, were replaced by chromosome 1E of the diploid wheatgrass. Since 1E has genes for FHB resistance we expect to produce FHB-tolerant durum substitution line. The two disomic substitution lines 1E(1A) and 1E(1B) that we developed were initially screened for FHB tolerance in the greenhouse. We are still awaiting the tabulation of the results from this initial screening. We have been consistently using molecular markers to identify individual group-1 chromosomes of durum and diploid wheatgrass. Large hybrid populations and their derivatives were thus screened for the presence of Ph1 and chromosome 1E. After screening the F2 and F3 generations of Cappelli (ph1cph1c) x DGE-1 we identified plants with chromosome 1E but they had Ph1 also and that prevents or reduces homoeologous recombination. We are still trying to obtain plants with chromosome 1E in the presence of ph1cph1c to induce segmental interchange between 1E and its counterpart in the durum complement. We are in the process of raising the F4 generation.
Improvement in durum wheat genetic resources. Durum wheat is used to make pasta and noodles and is widely used in the U.S., Canada, and several European countries. Current durum wheat cultivars lack resistance to a serious disease of cereals called Fusarium head blight (FHB). In attempts to transfer FHB resistance genes into durum from distant relatives, ARS researchers in Fargo, North Dakota, produced numerous hybrids between durum and distant relatives. They isolated unique genetic combinations and using appropriate DNA markers, confirmed substitutions of distant relative genes into durum. These new hybrids may be useful for imparting head blight resistance in durum cultivars and provide a new pool of important seed storage proteins. New sources of durum wheat resistance to head blight could help limit the spread and impact of this devastating disease and thereby increase profitability for US durum wheat producers, as well as reduce the input of pesticides into the environment.
Jauhar, P.P., Peterson, T.S. 2011. Cytological and Molecular Characterization of Homoeologous Group-1 Chromosomes in Hybrid Derivatives of a Durum Disomic Alien Addition Line. The Plant Genome. 4(2):102-109.
Jauhar, P.P. 2011. Genetic control of chromosome behaviour: Implications in evolution, crop improvement, and human biology. The Nucleus. 53:3-12.