**3. Results**

#### **3.1. Triticum monococcum**

Excellent reviews have been written listing the variability for resistance to FHB in alien spe‐ cies [14, 15–18, 34]. *T. monococcum* was not listed in those reviews. *T. monococcum* was one of the species screened for FHB resistance in our studies. We started by screening 200 accessions of *T. monococcum* that were obtained from M. Trottet of INRA. After repeated screening, line 10‐1 was identified as having a fair level of FHB resistance (**Figure 1**) [19, 20, 21]. Line 10‐1 was crossed to the spring wheat cultivar AC Domain. After repeated backcrossing and screening, line M321 was selected. The values for percent infected florets following point inoculation were 8% compared to 4% for the resistant check Sumai3 and 32% for Roblin the susceptible check. The DON content of M321 was 5.5 ppm compared to Sumai3 at 2.1 and Roblin at 17.2 (**Table 1**). M321 was crossed to AC Domain and a doubled haploid mapping population of 80 lines was produced by the maize pollination method [22]. A QTL for FHB resistance was located in chromosome 5A, linked to the marker Xwme705 [18].

The agronomic characteristics of line M321 are shown in **Table 1**. Line M321 compares favour‐ ably with check cultivars in terms of agronomic traits such as plant height, yield, thousand kernel weight (TKW), protein content and even flour yield. The grain yield of this line is reasonable compared to AC Barrie, a check cultivar. The data in **Table 1** indicate that there is minimal linking drag in M321. The lowered DON content relative to the checks could be a useful attribute for improvement of disease resistance of wheat.

#### **3.2. Aegilops speltoides**

FHB resistance was also sought in *Aegilops speltoides*. In this case, 50 accessions were screened and line S184 selected [19, 23]. It has previously been shown that different accessions of *Ae. speltoides* can lead to different levels of meiotic chromosome pairing in F1 hybrids with wheat. The hybrid


**Table 1.** Agronomic characteristics and DON content of FHB resistant lines introgressed into wheat from *T. monococcum* (M321) and *Ae. speltoides* (S184).

between AC Domain and the resistant speltoides accession showed an average of 3–4 bivalents at meiosis, i.e. the accession that we chose produced a high level of chromosome pairing in the F1 hybrid. The level of recombination between wheat chromosomes and those of *Ae. speltoides* would then be relatively high. Despite this, three backcrosses were required to restore fertility in the progeny. The agronomic characteristics of line S184 are shown in **Table 1**.

For most agronomic traits, such as plot yield, plant height protein content and even flour yield, the values for S184 compared favourably with the check cultivars (**Table 1**) [35]. Perhaps the most important attribute of this line is the lowered DON content. The DON content as shown in **Table 1** is 3.4 ppm compared to Sumai3 at 2.1, AC Barrie at 6.5 and Roblin at 17.2.

### **3.3. Triticum timopheevii**

were repeated 1 week later. An irrigation system was activated twice a day to maintain a high relative humidity to enhance sporulation of the inoculum. Flowering dates of each plot were recorded, defined as the stage of 50% anthesis. At 21 days after the flowering date, disease incidence and severity was estimated visually for each plot and recorded. FHB indices were calculated from these readings. The plots were hand harvested at physi‐

Threshing was done with a small plot thresher adjusted to retain the shrunken Fusarium damaged kernels (FDK). Two 1‐g aliquots were removed from each sample and ground in a Wiley mill. To ensure homogeneity of the aliquots, the seed was put through a seed divider. DON contents were estimated by an ELISA test using established methods [13]. Don contents of plots were expressed as parts per million. The check cultivars in field plots were Roblin as the susceptible check and Sumai3 as resistant. Other checks were selected as those that were

Excellent reviews have been written listing the variability for resistance to FHB in alien spe‐ cies [14, 15–18, 34]. *T. monococcum* was not listed in those reviews. *T. monococcum* was one of the species screened for FHB resistance in our studies. We started by screening 200 accessions of *T. monococcum* that were obtained from M. Trottet of INRA. After repeated screening, line 10‐1 was identified as having a fair level of FHB resistance (**Figure 1**) [19, 20, 21]. Line 10‐1 was crossed to the spring wheat cultivar AC Domain. After repeated backcrossing and screening, line M321 was selected. The values for percent infected florets following point inoculation were 8% compared to 4% for the resistant check Sumai3 and 32% for Roblin the susceptible check. The DON content of M321 was 5.5 ppm compared to Sumai3 at 2.1 and Roblin at 17.2 (**Table 1**). M321 was crossed to AC Domain and a doubled haploid mapping population of 80 lines was produced by the maize pollination method [22]. A QTL for FHB resistance was

The agronomic characteristics of line M321 are shown in **Table 1**. Line M321 compares favour‐ ably with check cultivars in terms of agronomic traits such as plant height, yield, thousand kernel weight (TKW), protein content and even flour yield. The grain yield of this line is reasonable compared to AC Barrie, a check cultivar. The data in **Table 1** indicate that there is minimal linking drag in M321. The lowered DON content relative to the checks could be a

FHB resistance was also sought in *Aegilops speltoides*. In this case, 50 accessions were screened and line S184 selected [19, 23]. It has previously been shown that different accessions of *Ae. speltoides* can lead to different levels of meiotic chromosome pairing in F1 hybrids with wheat. The hybrid

located in chromosome 5A, linked to the marker Xwme705 [18].

useful attribute for improvement of disease resistance of wheat.

ological maturity.

**3. Results**

parents of the various populations.

62 Wheat Improvement, Management and Utilization

**3.1. Triticum monococcum**

**3.2. Aegilops speltoides**

A resistant accession of *T. timopheevii* (AAGG genome) was crossed to the wheat cultivar Crocus which has all three crossability genes. The F1 was backcrossed to Crocus [24]. A popu‐ lation of 1500 BC1 F2 plants was established and 535 BC1F7 lines were developed in the green‐ house using single seed descent. One hundred lines were selected based on full plant fertility and good agronomic traits and evaluated for their FHB reaction in the field. The line TC67 was selected based on its enhanced FHB resistance (**Figure 2**) and good agronomic traits. To map the resistance trait, a mapping population was established by crossing TC67 to the mod‐ erately susceptible cultivar AC Brio. An F7 population of 230 RIL was established by SSD and evaluated for a number of FHB‐selected traits in field and greenhouse plantings.

As shown in **Table 2**, the DON content of TC67 and Brio was 1.3 and 3.0 ppm, respectively. The population mean for DON content was 2.2 with a range of 1.0–5.1 ppm. The QTL for this trait was mapped to chromosome 5A [25].

#### **3.4. Aegilops cylindrica**

*Aegilops cylindrica* is a tetraploid with the CCDD genome constitution. An accession collected in the wild by Alexander Rybalka of the Plant Breeding and Genetics Research Institute at Odessa Ukraine showed resistance to FHB. It was crossed to a local cultivar and a FHB resis‐ tant, stable derivative Cyl‐1 was selected in the progeny. In our tests that line gave DON ratings intermediate between Sumai3 and Roblin. The DON content of Cyl‐1 was 4.5 ppm

**Figure 2.** Resistance to Fusarium head blight expressed in TC67 an introgression from *T. timopheevii*. Disease symptoms expressed at 21 days after inoculation. Roblin is the susceptible check.


**Table 2.** FHB scores and DON content, means, ranges and heritability in a mapping population derived from TC67, a derivative from *Triticum timopheevii* and wheat cultivar Brio.

compared to Sumai3 and Roblin at 3.0 and 10.0, respectively. Cyl‐1 was crossed to North America cultivars AC Superb, AC Barrie and Alsen as shown in **Table 3**.

The populations were advanced to F4, F6 and F7. Progenies were grown in field plots and DON contents determined. The distribution of DON levels was similar for the three popula‐ tions. Although the DON levels in the checks Sumai3 and Roblin were at expected levels, the levels in the populations were unusually low and will need to be repeated.

Continued selection for a combination of improved agronomic traits and lower DON content resulted in line Odessa129‐2 with a DON content of 9.6 ppm compared to Sumai3 and AC Superb at 3.9 and 47.2, respectively.

### **3.5. Triticum miguschovae**

**Trait Parents Population mean Population range Heritability**

**Figure 2.** Resistance to Fusarium head blight expressed in TC67 an introgression from *T. timopheevii*. Disease symptoms

Disease incidence (%) 18.0 42.6 36.4 12.4–65.4 0.60 Disease severity (%) 41.3 41.8 50.8 25.5–76.7 0.47 FDK (%) 2.4 6.3 7.4 1.7–22.3 0.67 DON content (ppm) 1.3 3.0 2.2 1.0–5.1 0.69

5.1 35.1 35.2 5.1–99.2 0.89

**Table 2.** FHB scores and DON content, means, ranges and heritability in a mapping population derived from TC67, a

**TC 67 Brio**

expressed at 21 days after inoculation. Roblin is the susceptible check.

64 Wheat Improvement, Management and Utilization

derivative from *Triticum timopheevii* and wheat cultivar Brio.

Disease spread within the spike (%)

*Triticum miguschovae* is an amphiploid between *T. timopheevii* (AAGG genome) and *T. tauschii* (DD genome) [26, 27].

The spikes of the amphiploid display many alien species traits as shown in **Figure 3**. Following point inoculation with a 50,000 spores/ml, suspension of *Fusarium graminearum* spores, the symptoms did not spread beyond the inoculated floret (**Figure 3**). A similar display of symptoms was observed in BC2 progeny following backcrossing to AC Superb (**Figure 4**). AC Superb has no FHB resistance so the observed resistance must be contributed by the alien parent.

The progenies of BC2 plants were advanced to F5 with selections made on point inoculation symptoms at each generation.

A total of 35 F5 lines were grown in the epiphytotic nursery in single row plots and only one replicate. The DON content of the 35 lines ranged from 0.6 to 11.3 ppm (**Table 4**). Ten of the best F7 lines grown in the field gave a range of DON values of 3.5–8.2 ppm. The mean DON


*Note*: \* Cyl‐1 FHB‐resistant accession of *Aegilops cylindrical.*

**Table 3.** DON content of FHB‐resistant lines derived from progenies of *Aegilops cylindrical* crossed to wheat.

**Figure 3.** Resistance to Fusarium head blight expressed on spike of *Triticum miguschoae* (AGD) (R) at 21 days after inoculation. Roblin (L) is the susceptible check.

**Figure 4.** Symptoms on BC2 spike of hybrid between Superb and *T. miguschovae* at 21 days after point inoculation.


**Table 4.** FHB symptoms and DON content (ppm) in progenies from intercrosses of bread wheat cultivar AC Domain with *Triticum miguschovae*.

levels of the checks for the field tests were Sumai3 at 2.7 ppm, Fukuho at 13.5 ppm and AC Superb at 17.8 ppm.

Continued selection for a combination of improved agronomic traits and lower DON content resulted in the line MSB55 that had a DON content of 10.8 ppm compared to Sumai3 at 3.9 and AC Superb at 47.2.

#### **3.6. Tritordeum**

**Figure 3.** Resistance to Fusarium head blight expressed on spike of *Triticum miguschoae* (AGD) (R) at 21 days after

spike of hybrid between Superb and *T. miguschovae* at 21 days after point inoculation.

inoculation. Roblin (L) is the susceptible check.

66 Wheat Improvement, Management and Utilization

**Figure 4.** Symptoms on BC2

Resistance to FHB in durum wheat is very poor and variability for this trait in the tetra‐ ploid gene pool is very limited [28]. After screening some accessions of *Hordeum chilense* and detecting some variability for reaction to FHB, we crossed the better accessions to the durum cultivar Ma (which in our experience had better crossability than other durum cul‐ tivars). A chromosome preparation of the amphiploid is shown in **Figure 5**. Seven of the tri‐ tordeum amphiploids were evaluated for DON content and the results are shown in **Table 5**. Compared to Medora, a susceptible check, all seven amphiploids showed improved levels of DON content. Some of the values shown in **Table 5** are unrealistically low and should be

**Figure 5.** GISH pattern on a chromosome preparation from a Tritordeum (*Hordeum chilense* × *Triticum durum* amphiploid) showing 14 *Hordeum chilense* chromosomes (light color) and 28 durum chromosomes.


**Table 5.** DON content (ppm) of amphiploids between *Triticum turgidum* (AABB) and *Hordeum chilense* (HH).

re‐evaluated; however, this appears to be a potential source of lower DON levels. A variety of FHB responses are shown in **Figure 6**, following the point inoculation of four tritordeum amphiploids plus a Roblin check.

The amphiploids show normal meiotic behaviour, are stable and perfectly fertile with perfect transmission of all chromosomes. There is no meiotic pairing between *Hordeum chilense* chro‐ mosomes and those of wheat. In order to induce pairing between homoeologous chromosomes, the amphiploid was crossed to the Capelli *Ph* mutant then backcrossed once to place the mutant in a homozygous recessive condition. The progeny resulting from the *Ph* mutant treatment were further backcrossed and advanced to the BC3 F4 generation. Selection for reduced DON content and desirable agronomic traits was practiced during this procedure. Seventeen BC3 F4

**Figure 6.** FHB symptoms on spikes of Tritordeum lines at 21 days after inoculation.

lines were evaluated in the epiphytotic nursery, and results are shown in **Table 6**. The DON content in these lines ranged from 3.3 to 27.7 ppm compared to 19.1 for Strongfield the recur‐ rent parent. Derivatives from this process appeared to have lower symptoms.
