Phenotypic and genotypic characterization of CIMMYT’s 15th international Fusarium head blight screening nursery of wheat

As an important cereal disease in humid and semi-humid areas, Fusarium head blight (FHB) has caused severe epidemics on wheat (Triticum aestivum L.) in different countries worldwide. By causing both yield loss and quality degradation, FHB presents a two-fold threat to farmers and consumers. Since the beginning of FHB research at the International Maize and Wheat Improvement Centre (CIMMYT) in the early 1980s, a large-scale FHB screening has been conducted to identify and incorporate new resistance genes into elite CIMMYT germplasm. Candidates of the 15th Fusarium head blight screening nursery (FHBSN) were derived from different CIMMYT wheat breeding programs and were tested for 3 years successively in El Batan, Mexico, before being included in the 15th FHBSN set. From 2010 to 2012, a set of 44 out of 2794 lines were gradually selected depending on their FHB indices, pedigree information, and phenological traits like plant height and days to heading. The performance of these lines varied across years under different disease pressure, but they all showed high level of resistance compared to the susceptible checks. In 2013, the nursery was again evaluated in El Batan, as well as in artificially inoculated field trials in Norway, Uruguay, the Netherlands, and Japan (2014), and in naturally infected experiments in Toluca, Mexico, and Canada. Although not all lines demonstrated strong resistance across environments, promising lines with good FHB resistance can still be identified in each location. The genotypes were haplotyped with PCR-based markers for ten loci on seven chromosomes associated with known FHB resistance, and the results suggested that 24 of the genotypes (55 %) carried the 4BS QTL as in Wuhan 1, which was the most frequent QTL in this nursery, and the 7A QTL as in T. dicoccoides was noticed in five (11 %) of the genotypes. The resistance QTLs on chromosomes 3B, 5A and 6B as in Sumai 3 and 3A as in T. dicoccoides were not detected in any of the genotypes denoting the uniqueness of these lines. Fifteen (34 %) of the genotypes may not carry any of the ten QTLs examined. The results provide valuable information that could be successfully utilized by breeders to select resistant parents for crosses since novel resistance sources were detected for better targeted crosses toward diversifying and/or pyramiding FHB resistance.