Variation for stem solidness and its association with agronomic traits in spring wheat

The wheat stem sawfly (Cephus cinctus Norton) is a major insect pest of spring wheat (Triticum aestivum L.) in the Northern Great Plains of the US and Canadian Prairie provinces. The development of solid-stemmed wheat cultivars has been the main strategy to minimize losses from this insect. Solid-stemmed cultivars generally yield less than hollow-stemmed cultivars of the same era, and there are reports that degree of stem solidness is inversely related to grain yield. Our purpose was to examine the association between stem solidness and other agronomic traits and measure changes in progeny performance from three solid-stemmed parents representing different eras of cultivar development. Random, F-4-derived F-6 lines were obtained from crosses between solid-stemmed Rescue, Fortuna, and Lew and hollow-stemmed Newana and Thatcher. The random lines plus parents were evaluated in three environments. Changes during time from Rescue to Lew were in the desired direction for days to heading, plant height, and test weight, while stem-solidness score decreased for the parents themselves and in cross combination. Grain yield showed significant gains in two of three environments. A significant solid-stemmed x hollow-stemmed parent interaction was observed for stem solidness score suggesting epistatic gene action in the inheritance of this trait. The only significant associations of stem solidness score with agronomic traits were with plant height in one cross and grain protein concentration in two crosses. Results show the development of high yielding, solid-stemmed cultivars is not limited by undesirable associations between degree of stem solidness and other agronomic traits.