**4. Discussion**

**Line 2007 2008**

Ultima in the field nursery in 2007 and 2008.

70 Wheat Improvement, Management and Utilization

**3.8. Rye**

ing 104

Sul

*Note*: \*

related traits will be determined from these data.

produce octoploid amphiploids (as shown in **Table 9**).

Rye from Lagoon Vermellia, Rio di

DON levels in culture media (ppm).

Rye from Poula Frontin, Parana 10−5 S

White rye, Sao Paulo 10−3 R

**Accession DON\* Reaction to DON**

**Incidence (%) Severity (%) DON (ppm) Incidence (%) Severity (%) DON (ppm)**

**Table 7.** FHB symptoms and DON content of seven best resistant accessions of triticale and the checks Sumai3 and AC

mapping population in three replicates was grown at three locations in eastern Canada and data collected on incidence severity, FDK and DON content. The QTL for the various FHB

In screening of numerous accessions of rye from numerous sources, we were not able to find any lines with even minor improvements in FHB resistance. There were reports of Brazilian land races of rye with improved levels of FHB resistance [29]. The lines were evaluated for resistance by plating on media containing from 10−3 to 10−6 M levels of DON [32] to evaluate their levels of tolerance to DON. Lines that showed no variable effects on a medium contain‐

–10−3 M DON were considered to be resistant, whereas lines showing retarded growth on media containing 10−5–10−6 M levels of DON were considered to be susceptible. As shown in **Table 8**, the landraces from Poula Frontin were susceptible to DON, whereas landraces from Lagoon Vermellia and Sao Paulo gave a resistant reaction. A number of the resistant lines were used as pollen parents on wheat cultivars Encruzilhada, Maringa, Max and NyuBay to

10−4 R

**Table 8.** Tolerance of Brazilian rye landraces to deoxynivalenol (DON) following plating on DON‐containing media.

PI 355949 10.0 10.0 3.6 17.5 10.0 5.2 PI 428748 10.0 10.0 3.2 10.0 5.0 4.4 PI 428754 10.0 10.0 2.1 7.5 7.5 5.4 PI 428814 30.0 20.0 7.7 20.0 15.0 9.0 PI 428846 15.0 10.0 2.4 15.0 15.0 3.8 CN 42948 20.0 20.0 5.0 10.0 10.0 4.5 TMP 16315 15.0 15.0 4.1 20.0 10.0 5.2 Sumai3 5.0 5.0 1.2 5.0 5.0 3.2 AC Ultima 85.0 50.0 17.5 45.0 45.0 16.0

> Reviews have been written showing the variability for FHB resistance in alien species [14, 20]. Less information is available on variation for DON content in alien species [18].

> This review has shown that there are ranges for DON values in progenies obtained from sev‐ eral combinations of inter‐specific/inter‐generic hybrids. Although some of the data represent analyses from single years, there are indications of the potential of lowering the DON content by means of wide crosses.

> In all cases, the screening of alien species parents was initially conducted by point or spray inoculation. The progenies in most cases were screened by several methods. Perhaps a more concerted effort needs to be employed to initially screen wild species for DON content.

> Of various inoculation methods evaluated and methods of disease evaluation scored, including incidence, severity and FDK, it was found that DON evaluation gave the most reliable estimates of FHB resistance [14]. Considering that reducing DON content is the most important aspect of FHB resistance, DON evaluations should receive higher priority in future studies. Transgressive segregation for DON content was obtained in breeding populations of wheat and rye [30]. It was suggested that selection for lower DON content could be initiated as early as F3.

> Transgressive segregation for DON content was observed in populations described in this paper, especially in progenies of crosses to *T. timopheevii* derivatives.

> It has been shown by numerous studies beginning with Somers et al. [7] that DON content in wheat is controlled by distinctive QTL. That study also showed that minor QTL for DON content were present in the mapping population derived from Wuhan and NyuBay. These observations indicate that the potential exists for employing a combination of marker‐assisted

selection plus a high selection pressure in an epiphytotic nursery to increase the overall resis‐ tance to DON accumulations as has been done for visual symptoms QTL [31].

Detailed screening of alien species collections for DON content should be done to the same extent as screening for visual symptoms of FHB resistance. Preliminary results shown in this paper indicated that such an approach would be warranted, to be followed by mapping of additional QTL. Such QTL would very likely be unique and would add to the toolbox of resources available for breeding for reduced DON content.

In order to effectively transfer FHB resistance from alien species to wheat, sufficiently large populations need to be grown. It has been showed in numerous studies that sufficient number of major and minor QTL need to be transferred to obtain effective resistance.

In conclusion, these studies have shown considerable variability for DON content can be obtained from species relatives alien to wheat. A focussed approach would be required to tag the various QTL and systematically integrate them into bread wheat. This is anticipated to be an incremental process. The end products would be crop cultivars that would be resistant to the head scab phase of FHB with the added benefit of lower DON accumulation, making them more suitable for feed and food.
