Molecular Mapping of QTLs Conferring Fusarium Head Blight Resistance in Chinese Wheat Cultivar Jingzhou 66

Fusarium head blight (FHB) is a destructive disease of wheat (Triticum aestivum L.), which not only significantly reduces grain yield, but also affects end-use quality. Breeding wheat cultivars with high FHB resistance is the most effective way to control the disease. The Chinese wheat cultivar Jingzhou 66 (JZ66) shows moderately high FHB resistance; however, the genetic basis of its resistance is unknown. A doubled haploid (DH) population consisting 209 lines was developed from a cross of JZ66 and Aikang 58 (AK58), a FHB susceptible wheat cultivar, to identify quantitative trait loci (QTL) that contribute to the FHB resistance. Five field experiments were established across two consecutive crop seasons (2018 and 2019) to evaluate the DH lines and parents for FHB response. The parents and DH population were genotyped with the wheat 55K single-nucleotide polymorphism (SNP) assay. Six QTLs associated with FHB resistance in JZ66 were mapped on chromosome 2DS, 3AS, 3AL, 3DL, 4DS, and 5DL, respectively. Four of the QTL (QFhb.hbaas-2DS, QFhb.hbaas-3AL, QFhb.hbaas-4DS, and QFhb.hbaas-5DL) were detected in at least two environments, and the QTL on 3AL and 5DL might be new. The QTL with major effects, QFhb.hbaas-2DS and QFhb.hbaas-4DS, explained up to 36.2% and 17.6% of the phenotypic variance, and were co-localized with the plant semi-dwarfing loci Rht8 and Rht-D1. The dwarfing Rht8 allele significantly increased spike compactness (SC) and FHB susceptibility causing a larger effect on FHB response than Rht-D1 observed in this study. PCR–based SNP markers for QFhb.hbaas-2DS, QFhb.hbaas-3AL, QFhb.hbaas-4DS, and QFhb.hbaas-5DL, were developed to facilitate their use in breeding for FHB resistance by marker-assisted selection.

Genetics of Fusarium head blight resistance in three wheat genotypes

Fusarium head blight (FHB) is global concern as recent outbreaks reported in Canada, Europe, Asia, Australia and South America. The disease has emerged as one of the most important plant diseases worldwide in 21st century. One of the major threats posed by FHB fungus is the mycotoxin production which is harmful to human and animal health. Development of disease resistant cultivars is the only effective method for managing the disease. Control of these pathogen / Fusarium spp. is also challenging due to limited sources of known resistance. The famous Chinese wheat cultivar Sumai 3 and Frontana are the main sources of resistance to this disease. For genetic analysis and incorporation of FHB resistance into recently released high yielding wheat cultivars, HD 2967 and DPW 621-50, crosses were made with Sumai 3, Frontana and Aldan. The F2 plants from the crosses HD 2967/Frontana (140), HD 2967/Aldan (150), HD 2967/Sumai 3 (169) and DPW 621-50/Sumai 3 (182) were screened for resistance under controlled conditions. Disease score was recorded to identify resistant, moderately resistant and susceptible plants. The genetic ratios for resistance to FHB indicated a complex nature of resistance in all the three donors.

Identification of a major QTL and associated marker for high arabinoxylan fibre in white wheat flour

Dietary fibre (DF) has multiple health benefits, and wheat products are major sources of DF for human health. However, DF is depleted in white flour, which is most widely consumed, compared to wholegrain. The major type of DF in white wheat flour is the cell wall polysaccharide arabinoxylan (AX). Previous studies have identified the Chinese wheat cultivar Yumai 34 as having unusually high contents of AX in both water-soluble and insoluble forms. We have therefore used populations generated from crosses between Yumai 34 and four other wheat cultivars, three with average contents of AX (Ukrainka, Altigo and Claire) and one also having unusually high AX (Valoris), in order to map QTLs for soluble AX (determined as relative viscosity) of aqueous extracts of wholemeal flours) and total AX (determined by enzyme fingerprinting of white flour). A number of QTL were mapped, but most were only detected in one or two crosses. However, all four crosses showed strong QTLs for high RV/total AX on chromosome 1B, with Yumai 34 being the increasing parent, and a KASP marker for the high AX Yumai 34 allele was validated by analysis of high AX lines derived from Yumai 34 but selected by biochemical analysis. A QTL for RV was mapped on chromosome 6B in Yumai 34 × Valoris, with Valoris being the increasing allele, which was consistent with the observation of transgressive segregation for this trait. The data indicate that breeding can be used to develop wheat with high AX fibre in white flour.

Molecular mapping of leaf rust resistance gene LrL224 in Chinese wheat cultivar L224-3

Leaf rust, caused by Puccinia triticina, is a major wheat disease worldwide. The chinese wheat cultivar L224-3 showed high resistance to most of P. triticina pathotypes in the seedling and adult stage. Identifying and mapping the leaf rust resistance gene(s) in L224-3 is very useful for breeding leaf rust resistant wheat cultivars. In the present study, the wheat cultivar L224-3 and thirty-six lines with known leaf rust resistance genes were inoculated with 15 pathotypes at the seedling stage for gene postulation. A total of 144 F_2:3 lines from the cross L224-3 × Zhengzhou 5389 were inoculated with the pathotype FHBQ for leaf rust genetic analysis at the seedling stage. A total of 1276 SSR (simple sequence repeat) markers and the STS (sequence tagged-site) marker ω-secali/Glu-B3 were used to test the parents, resistant and susceptible bulks. The polymorphic markers were used to genotype the F_2:3 populations. L224-3 was highly resistant to all Lr26 avirulent pathotypes, showing the presence of Lr26 in L224-3. The presence of Lr26 in L224-3 was also confirmed by the molecular marker ω-secalin/Glu-B3. Due to resistance to some Lr26 virulent pathotypes, L224-3 may carry another resistance gene. Based on the genetic analysis using the pathotype FHBQ with virulence to Lr26 the resistance of L224-3 was controlled by a single dominant gene, tentatively designated LrL224. Four SSR markers (barc8, gwm582, wmc419, and wmc694) and one STS marker (ω-secali/Glu-B3) on 1B were closely linked to LrL224. The two flanking SSR loci were barc8 and gwm582, with the genetic distances of 4.3 and 4.6 cM, respectively. LrL224 was located on 1BL, and it showed different seedling reactions with other genes on 1B. Therefore LrL224 is likely to be a new leaf rust resistance gene.