Mapping QTL for Fusarium head blight resistance in a tunisian-derived durum wheat population

Fusarium head blight (FHB) damage in durum wheat (Triticum turgidum L. var. durum Desf., turgidum) inflicted massive economic losses worldwide. Meanwhile, FHB resistant durum wheat germplasm is extremely limited. ‘Tunisian108’ is a newly identified tetraploid wheat with FHB resistance. However, genomic regions in ‘Tunisian108’ that significantly associated with FHB resistance are yet unclear. Therefore, a population of 171 backcross inbred lines (BC1F7) derived from a cross between ‘Tunisian108’ and a susceptible durum cultivar ‘Ben’ was characterized. Fusarium graminearum (R010, R1267, and R1322) was point inoculated (greenhouse) or spawn inoculated (field) in 2010 and 2011. Disease severity, Fusarium-damaged kernel (FDK) and mycotoxins were measured. Analysis of variance showed significant genotype and genotype by environment effect on all traits. Approximately 8% of the lines in field and 25% of the lines in greenhouse were more resistance than Tunisian108. A framework linkage map of 267 DArt plus 62 SSR markers was developed representing 239 unique loci and covering a total distance of 1887.6 cM. Composite interval mapping revealed nine QTL for FHB severity, four QTL for DON, and four QTL for FDK on seven chromosomes. Two novel QTL, Qfhb.ndsu-3BL and Qfhb.ndsu-2B, were identified for disease severity, explaining 11 and 6% of the phenotypic variation, respectively. Also, a QTL with large effect on severity and a QTL with negative effect on FDK on chromosome 5A were identified. Importantly, a novel region on chromosome 2B was identified with multiple FHB resistance. Validation on these QTL would facilitate the durum wheat resistance breeding

Genome-Wide Association Mapping for Yield and Related Traits Under Drought Stressed and Non-stressed Environments in Wheat

Understanding the genetics of drought tolerance in hard red spring wheat (HRSW) in northern USA is a prerequisite for developing drought-tolerant cultivars for this region. An association mapping (AM) study for drought tolerance in spring wheat in northern USA was undertaken using 361 wheat genotypes and Infinium 90K single-nucleotide polymorphism (SNP) assay. The genotypes were evaluated in nine different locations of North Dakota (ND) for plant height (PH), days to heading (DH), yield (YLD), test weight (TW), and thousand kernel weight (TKW) under rain-fed conditions. Rainfall data and soil type of the locations were used to assess drought conditions. A mixed linear model (MLM), which accounts for population structure and kinship (PC+K), was used for marker–trait association. A total of 69 consistent QTL involved with drought tolerance-related traits were identified, with p ≤ 0.001. Chromosomes 1A, 3A, 3B, 4B, 4D, 5B, 6A, and 6B were identified to harbor major QTL for drought tolerance. Six potential novel QTL were identified on chromosomes 3D, 4A, 5B, 7A, and 7B. The novel QTL were identified for DH, PH, and TKW. The findings of this study can be used in marker-assisted selection (MAS) for drought-tolerance breeding in spring wheat

Genetic and molecular analysis of wheat tan spot resistance effective against Pyrenophora tritici-repentis races 2 and 5

Tan spot, a major foliar disease of wheat (Triticum aestivum L.), is caused by an ascomycete Pyrenophora tritici-repentis. Both culture filtrates and conidiospore inocula induce disease symptoms in susceptible wheat genotypes. The objectives of this study were to determine and map the genetic control of resistance to spore inocula and culture filtrates of P. tritici-repentis races 2 and 5. The F1 and F2 generations and an F2:6 recombinant inbred lines (RIL) population were developed from a cross between the resistant ND 735 and the susceptible Steele-ND. Disease assessments of the segregating generations were done at the seedling stage using culture filtrates and spore inocula under controlled environmental conditions. Genetic and mapping analyses of the F1 and F2 generations and the RIL by both methods indicated that the same single recessive gene, Tsr1, located on chromosome 5BL, controlled resistance and insensitivity to necrosis induced by race 2. A second recessive gene, designated Tsr6, located on chromosome 2BS, conferred resistance/insensitivity to chlorosis induced by spore inocula or culture filtrates of race 5. Diversity Arrays Technology markers wPt-3049 (2.9 cM) and wPt-0289 (4.6 cM) were closely linked to Tsr1 and Tsr6, respectively. The results further indicated that culture filtrates can be used as surrogates for spore inoculation. Tsr1 and Tsr6 can be selected by marker-assisted selection in breeding for resistance to tan spot