Identification of candidate genes for traits of relevant breeding value transferred from a wild relative to wheat.

Two valuable genes for durum wheat breeding, i.e. Lr19 (leaf-rust resistance) and Yp (yellow endosperm pigmentation), closely linked on the 7AgL chromosome arm of the perennial wheatgrass species Thinopyrum ponticum, have been transferred to the 7AL durum wheat arm by chromosome engineering. Using a ‘NBS profiling’ assay to target Lr19, and a comparative genomics approach for Yp, candidate genes for both traits have been identified

Transfer of a major qtl for resistance to fusarium head blight from Thinopyrum elongatum onto durum wheat 7al chromosome arm and its pyramiding with other useful genes from Th. ponticum

Fusarium Head Blight (FHB), also called scab, a major wheat disease worldwide, has in recent years become a threat also in uncommon cultivation areas of bread and durum wheat. The lack of efficient and durable sources of resistance within adapted durum wheat germplasm is particularly alarming. In fact, durum wheat is used almost exclusively for human consumption, and Fusarium attacks, besides causing severe yield losses, pose a high risk of kernel contamination with health-dangerous mycotoxins, notably deoxynivalenol (DON). To cope with this scenario, looking outside of the primary genepool and exploring exotic variability harboured within related Triticeae species, appears as a worth strategy. We recently mapped an exceptionally effective QTL for FHB resistance (provisional designation Fhb-7EL) onto the telomeric portion of the 7EL chromosome arm of diploid Thinopyrum elongatum, and pyramided it with other useful genes from the 7el1L arm of decaploid Th. ponticum (Lr19, Yp, yield related traits) onto the 7DL arm of bread wheat- Thinopyrum recombinant lines (Ceoloni et al. TAG, in press). Two such FHB resistant recombinants, having distal 70% of their 7DL replaced by chromatin of the two Thinopyrum species in slightly different relative proportions, were crossed with two previously developed durum wheat- Th. ponticum recombinants, having 23% and 28% of their 7AL arm replaced by 7el1L chromatin, respectively. In the shared 7el1L region between the bread wheat (6x) and durum wheat (4x) parental recombinant types, including in all cases the Lr19 gene, homologous pairing evidently occurred with high frequency (over 70%), as proved by GISH-based analysis of meiotic pairing of 5x F1\u2019s. As a result, new 7EL-7el1L recombinant types could be isolated in the BC1 generation to durum wheat. Selection for desired recombinants, i.e. those involving chromosome 7A and with a total Thinopyrum spp. (7EL+7el1L) chromatin not exceeding the 28% of the arm, was carried out by a panel of user-friendly PCR-based markers. To accelerate reduction of chromosome number to the euploid 2n=28, in vitro culture of BC2 embryos was carried out. Selected heterozygous recombinant plants, most of them having reached a stable chromosomal condition, were selfed and in the BC2F2 progeny homozygous genotypes were isolated. The latter were challenged by Fusarium graminearum spike inoculation, to verify the efficacy of the Fhb-7EL QTL once inserted into a durum wheat background. Compared to highly susceptible control plants, inoculation outcomes confirmed what previously observed at the bread wheat level, with remarkable reduction of disease severity, averaging over 90%, invariably associated with presence of the Fhb-7EL QTL. Thus, what is considered to be by far the most effective resistance to FHB available, is now readily exploitable in breeding to provide protection against this threatening disease, hence substantially enhancing food security and safety of the bread and durum wheat crop, in Italy and worldwide

Reinforcing and broadening resistance against Fusarium diseases in durum wheat by an udp-glucosyltransferase transgene and its pyramiding with a pectin methyl esterase inhibitor transgene

Many species of the genus Fusarium are phytopathogenic fungi of a wide range of cereal crop plants, including wheat. F. graminearum is the main causal agent of Fusarium Head Blight (FHB), while F. culmorum and F. pseudograminearum are the main responsible species of Fusarium Crown Rot (FCR). Fusarium diseases represent major agricultural problems worldwide, causing reduction of grain yield, grain quality and food safety. The latter is associated with contamination of grains with mycotoxins, particularly deoxynivalenol (DON), which cause health problems in humans and animals. DON is a protein synthesis inhibitor, acting as a virulence factor during pathogenesis and resulting essential for fungal spread along the spike. Conversion of DON to deoxynivalenol-3-\u3b2-D-glucoside (D3G) by the activity of specific UDP-glucosyltransferases (UGTs), is one of the mechanisms involved in enhancing plant tolerance to DON. Previous studies demonstrated that the expression of the barley HvUGT13248 gene confers resistance to DON in Arabidopsis thaliana (Shin et al. 2012, J Exp Bot. 63:4731-40) and type II resistance to FHB (i.e. resistance to fungal spread within host tissues) in bread wheat (Li et al. 2015, MPMI 28:1237-46). Improvement of FHB resistance is a major target in both bread and durum wheat. The latter, however, is especially vulnerable, as effective sources of resistance are particularly limited. Therefore, we decided to verify whether the expression of the HvUGT13248 gene could enhance FHB resistance in durum wheat as well. To this aim, transgenic lines of Triticum durum cv. Svevo, constitutively expressing the HvUGT13248 gene, were produced. Transgenic plants in which presence of transcript and protein was confirmed, were infected with F. graminearum and evaluated for FHB severity, DON content and D3G conversion as compared to wild type plants. Our results showed that the HvUGT13248 gene determines in durum wheat a significant reduction of FHB symptoms (up to 30%) compared to control plants. This effect, however, was mainly evident at early infection stages, progressively decreasing at later stages. This outcome differs from what observed in transgenic bread wheat expressing the same UGT gene, in which FHB severity did not exceed 20% up to the last stages of infection (Li et al. 2015). To verify further the effectiveness of the DON-detoxifying approach, durum wheat lines with the same HvUGT13248 transgene were challenged with F. culmorum, also able to produce DON. A significant reduction of FCR symptoms compared to Svevo plants was observed. This represents the first report of improvement of FCR resistance associated with overexpression of an UGT involved in DON-detoxification. Recently, in order to combine in the same plant genes controlling two different mechanisms of type II resistance to FHB, we have crossed two types of durum wheat transgenic lines, one expressing the HvUGT13248 gene, the other AcPMEI, coding for a kiwi pectin methyl esterase inhibitor, known to increase resistance by strengthening the cell wall pectin fraction. On selected carriers of both transgenes, and in control lines with individual or no transgenes, the efficacy of the novel assembly will be verified against FHB and FCR

Durum wheat-Thinopyrum ponticum recombinant lines: a tool to finely describe homoeologous 7L arm regions.

As one important result of wheat chromosome engineering, creation of arrays of wheat-alien recombinant chromosomes allows assignment of markers and genes to defined physical locations, hence improving knowledge of structural-functional organization of wheat and alien chromosomal regions and to identify suitable markers for MAS of target genes. Regions involved in our research are the distal portions of wheat 7AL and Thinopyrum ponticum (tall wheatgrass, a wild wheat relative) 7AgL arms, the latter containing several genes of value for wheat improvement