CEREALES, OLEOPROTEAGINEAUX ET, MAIS - CEROM
Cereal, Oilseed and Protein Crops, and Maize Research Centre, 335 Chemin des Vingt-Cinq, St-Bruno-de-Montarville, Québec, J3V 4P6, Canada.
Yves Dion, Sylvie Rioux, André Comeau *, Luc Couture *, François Langevin **, Harvey Voldeng ***, Jeannie Gilbert ****, Steve Haber ****, and Jean-Pierre Dubuc *****.
* Research Centre, Agriculture and Agri-Food Canada, Ste-Foy, Qc, G1V 2J3; ** 121 Bon-Air, Ste-Catherine-de-la-Jacques-Cartier, Qc, G0A 3M0; *** Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, On, K1A 0C6; **** Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, Man, R3T 2M9; and ***** 1499 rue J.C. Cantin, Cap-Rouge, Qc, G1Y 2X7.
Efforts to develop germ plasm and cultivars resistant to FHB were initiated in 1979 in Quebec. After a long struggle with the genetic complexity of the problem, those efforts are now yielding results. Crosses initiated by Dr. Jean-Pierre Dubuc at AAFC Ste-Foy and selected with the help of Dr. Luc Couture (Ste-Foy) and Alain Devaux (MAPAQ) led to lines that were confirmed as resistant in the hands of scientists from ECORC, CRC, and CEROM. Among the examples of recent success, one must quote a line that was supported for registration in 2002, CRGB-O-623.4. This line embodies a good package of valuable traits, but is very susceptible to rusts and powdery mildew. The FHB resistance is about midway between that of AC Barrie and Sumai 3, and the yield is quite adequate in the province of Quebec.
The pedigree of the line is 'AC Pollet/QW539.8//QW526.17/QW530.2'. The expanded pedigree is 'Frontana LF320//Concorde/Opal/3/Glenlea/Minaret/4/Ciano79/Anza//Ciano79/82Pch794/3/unknown QW line/Nobeoka Bouzu'. The intermediate line QW530.2 was derived from the cross of an unknown QW line to Nobeoka Bouzu. The presence of an unknown QW line is due to the former use of a composite cross approach for germ plasm development, whenever the probability of success was considered low. This method reduces the number of accessions to be handled, but causes a loss of precise pedigree information. However, the unknown QW line was probably not a significant source of FHB resistance. The line QW530.2 was verified to possess approximately twice the number of infected spikelets (28 % versus 14 %) when compared to Nyu Bai, a resistant line that is genetically very similar to Nobeoka Bouzu. In the same trials, the susceptible check Roblin had 43 % infected spikelets and the susceptible check Max, 64 %. Thus, QW530.2 had approximately half of the resistance of a very resistant parent from Japan. The end result, however, which is CRGB-O-623.4, now appears to be quite close to Nyu Bai in terms of resistance. Nyu Bai is still more resistant, but the difference is not statistically significant based on the current data set (seven test sites). We therefore hypothesize that CRGB-O-623.4 has integrated other genes of FHB resistance from the other possible sources.
Among possible resistance sources, Frontana LF 320 is noteworthy; a Frontana reselection obtained by Alain Devaux circa 1980. This reselection has been widely used in Canada and, perhaps, elsewhere, labeled simply as 'Frontana'. Scientists in Brazil have confirmed that Frontana itself is a F4-derived line in which genetic biodiversity is still present (Cantidio de Sousa, pers comm). The same comment applied to many Brazilian cultivars and, especially, to the older ones.
Frontana LF 320 is a well-documented source of type 1 resistance (to infection) to FHB. The line also is capable of degrading trichothecenes, according to Miller and Arnison (1986). Nobeoka Bouzu is a source of type-II resistance (to spread). The use of sources of type-II resistance often leads to problems of low biomass, low root biomass, and low yield. That trend has been verified repeatedly but never properly explained. Germ plasm that has BYDV tolerance shows the contrary trend, since BYDV tolerance is associated with high biomass, high root biomass, and high yield if the lodging is not severe. One parent of CRGB-O-623.4 is a Ste-Foy BYDV-tolerant line based on CIMMYT germ plasm (QW526.17, derived from 'Ciano79/Anza//Ciano79/82Pch794'). Verifying whether BYDV tolerance could offset the biomass problems of type-II, FHB-resistant wheats thus becomes an interesting research avenue, currently explored in a collaborative effort at some Canadian research centers.
Creating usable derivatives of Nobeoka Bouzu is not easy. Because QW530.2 proved to be a valuable parental line, 12-year-old seed of QW530.2 was retrieved. The original seed had only 0.1 % germination, thus, it will need to be increased before being sent to the Canadian germ plasm bank (Plant Gene Resources, Saskatoon). Efforts to diversify the sources of FHB resistance also are under way with the help of CEROM and many AAFC Centres (Winnipeg, Swift Current, Lethbridge, Ottawa, and Charlottetown). Most sources of FHB resistance prior to 2001 were all very susceptible to BYDV and Pythium root rot. Sources that offer FHB resistance together with resistance to other diseases have been identified in Brazilian wheats, i.e., EMBRAPA 27 and BRS 177. However, these two cultivars carry genes that reduce bread-making quality. Attempts to introgress genes from interspecific origin also are under way. We hope the current success can serve as a basis for further progress.