High density mapping and haplotype analysis of the major stem-solidness locus SSt1 in durum and common wheat

Abstract

Breeding for solid-stemmed durum (Triticum turgidum L. var durum) and common wheat (Triticum aestivum L.) cultivars is one strategy to minimize yield losses caused by the wheat stem sawfly (Cephus cinctus Norton). Major stem-solidness QTL have been localized to the long arm of chromosome 3B in both wheat species, but it is unclear if these QTL span a common genetic interval. In this study, we have improved the resolution of the QTL on chromosome 3B in a durum (Kofa/W9262-260D3) and common wheat (Lillian/Vesper) mapping population. Coincident QTL (LOD = 94–127, R2 = 78–92%) were localized near the telomere of chromosome 3BL in both mapping populations, which we designate SSt1. We further examined the SSt1 interval by using available consensus maps for durum and common wheat and compared genetic to physical intervals by anchoring markers to the current version of the wild emmer wheat (WEW) reference sequence. These results suggest that the SSt1 interval spans a physical distance of 1.6 Mb in WEW (positions 833.4–835.0 Mb). In addition, minor QTL were identified on chromosomes 2A, 2D, 4A, and 5A that were found to synergistically enhance expression of SSt1 to increase stem-solidness. These results suggest that developing new wheat cultivars with improved stem-solidness is possible by combining SSt1 with favorable alleles at minor loci within both wheat species.

Sorghum stem aerenchyma formation is regulated by SbNAC_D during internode development

“…Greater divergence was observed across the C‐terminal portion of the grass NAC_D ‐like proteins consistent with what has been found for other NAC proteins. The large N‐terminal deletion present in a NAC_D homolog of wheat may be a consequence of selection for solid stems in this grain crop (Nilsen et al., ). A NAC_D homolog of sugarcane was also truncated, which may contribute to reduced aerenchyma formation in stems of sugarcane (Figure ).…”

“…In sugarcane, selection for inactive alleles of NAC_D is consistent with low levels of stem aerenchyma, high stem juiciness, and high stem sucrose content in that crop (Waclawovsky, Sato, Lembke, Moore, & Souza, ). Selection for more solid stems has also occurred in wheat in part to increase resistance to insects that damage stems although the genetic basis of insect resistance is complex (Nilsen et al., ).…”

“…The extent of aerenchyma (AER) formation was rated by visual inspection of cross sections of internodes taken approximately at the midpoint between nodes. Ratings were based on a scale from 1 to 5 (1, no AER; 5, high AER) in a manner similar to prior studies () (Carvalho & Rooney, ; Nilsen et al., ). Results from visual rating were similar to ratings based on a percent of area calculation when data were used for QTL analysis (Carvalho & Rooney, ).…”

“…The large N-terminal deletion present in a NAC_D homolog of wheat may be a consequence of selection for solid stems in this grain crop (Nilsen et al, 2017). A NAC_D homolog of sugarcane was also F I G U R E 4 Protein sequence alignment of SbNAC_D homologs in select grass species.…”

Agronomic Advancement in Tillage, Crop Rotation, Soil Health, and Genetic Gain in Durum Wheat Cultivation: A 17-Year Canadian Story

“…The genetics of solid stem trait, which confers resistance to the wheat stem sawfly, has been studied in durum wheat [190]. A major gene for stem solidness, SSt1, has been localized on chromosome 3BL in a durum doubled haploid population of Kofa/W9262-260D3, and minor QTL on chromosomes 2A and 4A that explained 0.2-0.3% of the phenotypic variance [191]. AAC Raymore and CDC Fortitude [165] were the first solid stem durum cultivars which confer resistance to the wheat stem sawfly (Table 1).…”