Separation of the effects of two reduced height (Rht) genes and genomic background to select for less Fusarium head blight of short-strawed winter wheat (Triticum aestivum L.) varieties

Abstract

Key message FHB resistance shared pleiotropic loci with plant height and anther retention. Genomic prediction allows to select for genomic background reducing FHB susceptibility in the presence of the dwarfing allele Rht-D1b. Abstract With the high interest for semi-dwarf cultivars in wheat, finding locally adapted resistance sources against Fusarium head blight (FHB) and FHB-neutral reduced height (Rht) genes is of utmost relevance. In this study, 401 genotypes of European origin without/with dwarfing alleles of Rht-D1 and/or Rht24 were analysed across five environments on FHB severity and the morphological traits such as plant height (PH), anther retention (AR), number of spikelets per ear, ear length and ear density. Data were analysed by combined correlation and path analyses, association mapping and coupling single- and multi-trait genome-wide association studies (ST-GWAS and MT-GWAS, respectively) and genomic prediction (GP). All FHB data were corrected for flowering date or heading stage. High genotypic correlation (rg = 0.74) and direct path effect (0.57) were detected between FHB severity and anther retention (AR). Moderate correlation (rg = − 0.55) was found between FHB severity and plant height (PH) with a high indirect path via AR (− 0.31). Indirect selection for FHB resistance should concentrate on AR and PH. ST-GWAS identified 25 quantitative trait loci (QTL) for FHB severity, PH and AR, while MT-GWAS detected six QTL across chromosomes 2A, 4D, 5A, 6B and 7B conveying pleiotropic effects on the traits. Rht-D1b was associated with high AR and FHB susceptibility. Our study identified a promising positively acting pleiotropic QTL on chromosome 7B which can be utilized to improve FHB resistance while reducing PH and AR. Rht-D1b genotypes having a high resistance genomic background exhibited lower FHB severity and AR. The use of GP for estimating the genomic background was more effective than selection of GWAS-detected markers. We demonstrated that GP has a great potential and should be exploited by selecting for semi-dwarf winter wheat genotypes with higher FHB resistance due to their genomic background.

The importance of Fusarium head blight resistance in the cereal breeding industry: Case studies from Germany and Austria

“…The highest prediction ability was found for GBLUP + AnthesisDate + Rht‐D1 (PA = 0.87 ± 0.03), followed by GBLUP + AntherRetention + Rht‐D1 (PA = 0.84 ± 0.04) in a fivefold cross‐validated procedure. This again highlights the importance of integration of morphological traits for FHB resistance that was also reported elsewhere (Akohoue et al, 2022; Buerstmayr & Buerstmayr, 2016; Lu et al, 2013).…”

“…Moreover, in the meantime, we know that Rht‐B1b and Rht‐D1b both increase anther retention (Buerstmayr & Buerstmayr, 2016) that might be an important part of the dwarfing gene's enhancement of FHB susceptibility. A recent path analysis within the European winter wheat diversity panel showed that the morphological factors plant height and anther retention have a narrow genotypic correlation with FHB severity ( r g = −.64 and .74, respectively) and explain together 67% of the phenotypic variation for FHB severity (Akohoue et al, 2022). A 1% higher anther retention caused a 0.57% higher FHB severity.…”

Green Revolution dwarfing Rht genes negatively affected wheat floral traits related to cross‐pollination efficiency

“…These authors also suggested that, while Rht ‐ D1a could be used as elite pollinators, the semi‐dwarf Rht2 could be fixed in the female pool, and due to the semi‐dominant inheritance of this allele, the resulting hybrids would possess the desired plant height reduction (Boeven et al., 2016; Börner et al., 1996; Zhao et al., 2014). The exploration of modern Green Revolution Rht genes such as Rht24b has shown the potentiality of decreasing plant height without penalties in grain yield (Tian et al., 2022) while increasing anther extrusion and resistance against Fusarium head blight compared to the Green Revolution semi‐dwarf allele Rht2 (Akohoue et al., 2022; Miedaner et al., 2022; Würschum et al., 2017).…”

Approaching 25 years of progress towards Fusarium head blight resistance in southern soft red winter wheat (Triticum aestivum L.)

“…and Rht-D1, and not as a general relationship between the two phenotypes (Akohoue et al, 2022;Srinivasachary et al, 2008;Voss et al, 2008). Both homeologous copies of Rht1 encode DELLA proteins that, beyond their role in directly regulating the gibberellic acid response, additionally interact with signalling pathways implicated in plant response to biotic stress (Navarro et al, 2008).…”

“…A decrease in mature plant height may bring wheat heads closer to the soil surface and increase exposure of plants to rain‐splashed pathogens. Recent work however has suggested a link between plant height reduction and increased FHB susceptibility primarily as a result of using green revolution genes Rht‐B1 and Rht‐D1 , and not as a general relationship between the two phenotypes (Akohoue et al, 2022; Srinivasachary et al, 2008; Voss et al, 2008). Both homeologous copies of Rht1 encode DELLA proteins that, beyond their role in directly regulating the gibberellic acid response, additionally interact with signalling pathways implicated in plant response to biotic stress (Navarro et al, 2008).…”