Maria Buerstmayr & Hermann Buerstmayr

Theoretical and Applied Genetics June 2022; vol. 135: 1985–1996

Key message

The effect of the Rht1-genes on FHB resistance depends on anther extrusion and level of background resistance. Qfhs.ifa-5A increases resistance and anther extrusion as efficiently as semi-dwarfing alleles decrease it.

Abstract

The semi-dwarfing reduced height alleles Rht-D1b and Rht-B1b have been deployed in modern wheat cultivars throughout the world, but they increase susceptibility to Fusarium head blight (FHB). Here, we investigated the impact of the Rht1 genes on anther retention (AR) in relation to FHB resistance using four different sets of near-isogenic lines (NILs) with contrasting levels and types of background FHB resistance. NILs were evaluated for FHB severity, plant height and AR in three greenhouse and three field trials using artificial spray inoculation. Rht-B1b and Rht-D1b alleles increased AR and FHB susceptibility in all genetic backgrounds. The magnitude of the effects differed between NIL groups. Increased FHB susceptibility largely followed increased AR. Differences in FHB susceptibility between tall and dwarf haplotypes were largest in the NIL group with the highest changes in AR. In the most resistant NIL group, dwarfed lines had only slightly higher AR than tall lines and maintained good resistance, while both tall and dwarf lines had high levels of retained anthers in the most susceptible NIL group. We further investigated the effect of the major Fusarium resistance QTL Fhb1 and Qfhs.ifa-5A in combination with the Rht1 genes. Qfhs.ifa-5A enhanced anther extrusion in tall as well as semi-dwarf haplotypes, whereas Fhb1 did not affect AR. Qfhs.ifa-5A supported FHB resistance more efficiently than Fhb1 in lines that were more responsive to AR, while both Fhb1 and Qfhs.ifa-5A were equally efficient in NILs that had high background resistance and low.

See: https://link.springer.com/article/10.1007/s00122-022-04088-x

Figure 1: Boxplots of near isogenic lines (NILs) grouped by Rht1 allele status for the recurrent NIL groups RE-NIL1, CM, FRxRE and MI for plant height, anther retention, FHB incidence, and area under the disease progress curve (AUDPC). Medians are indicated by solid bold lines and outliers by open circles. Comparisons are based on best linear unbiased estimators (BLUEs) across field trials. Bonferroni correction was used to adjust for multiple pairwise contrasts. Different letters below BLUEs indicate significant differences among NIL groups (p < 0.05), and bars between boxes indicate significant differences among Rht1 haplotypes within NIL groups. Signif. codes: ***p < 0.001; **0.001 < p < 0.01; *0.01 < p < 0.05. Interaction plots depict BLUEs and standard errors of Rht1 haplotypes by NIL group interaction