2012 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.
Although durum wheat is one of the most important cereal crops in the country, especially in North Dakota, there is no reliable source of FHB resistance in the current durum cultivars. We discovered that diploid wheatgrass (Lophopyrum elongatum), in the tertiary gene pool of durum wheat, is an excellent source of FHB resistance. We, therefore, tapped this grass for breeding FHB resistance into durum cultivars. Through chromosome engineering, we produced a durum alien addition line of the cultivar Langden by introducing in it a double dose of chromosome 1E. This addition line has an enhanced tolerance to FHB and the gene(s) for FHB resistance are located in the chromosome 1E. We released this alien addition as a genetic stock DGE-1 in 2008. We further produced a disomic alien substitution line in which chromosome 1A was substituted by 1E. This substitution was released as a genetic stock DGE-2 in 2011. We have produced another disomic alien substitution in which second homoeologue 1B in the group-1 was replaced by 1E. This substitution is being released as a genetic stock DGE-3. These genetic stocks will be useful in basic studies on FHB resistance.
We have been successful in associating molecular markers to individual chromosomes in the durum homoeologous group-1 and to chromosomes of diploid wheatgrass. Thus, we were able to identify the grass chromosomes added into durum wheat. Based on chromosome pairing, we were successful in assessing genomic relationships.
New genetic stock of durum wheat. Fusarium Head Blight (FHB) is a very damaging disease of durum wheat, an important cereal crop in the upper Midwest of the United States. However, there is no reliable source of FHB resistance for current durum cultivars. ARS researchers in Fargo, North Dakota used a diploid wild grass species as a source of FHB resistance to produce plants in which one pair of durum chromosomes was replaced by a pair of grass chromosomes. Seed from this new genetic stock, called DGE-3, has been deposited at the National Center for Genetic Resources Preservation Center, Fort Collins, Colorado. Molecular markers are very useful in distinguishing durum chromosomes from grass chromosomes and therefore can accelerate resistance breeding work. This unique genetic stock will be particularly useful in basic research on FHB resistance in durum wheat.
Jauhar, P.P., Peterson, T.S. 2012. Registration of DGE-2, a durum wheat disomic alien substitution line 1E(1A) involving a diploid wheatgrass chromosome. Journal of Plant Registrations. 6:221-223.
Jauhar, P.P. 2012. Polyploidy in relation to plant speciation and evolution. In: Sharma, A.K., editor. Biological Diversity: Principles and Processes. New Delhi, India: Viva Books Pvt. Limited. p. 13-31.
Jauhar, P.P., Peterson, T.S. 2012. Synthesis and cytological analyses of hybrids between hexaploid wheat, with and without Ph1, and diploid wheatgrass. The Nucleus. 54:57-63.