Sowing density and cultivar effects on pith expression and yield in solid-stemmed durum wheat.
Nilsen, K.T., Clarke, J.M., Beres, B.L., and Pozniak, C.J. (2016). "Sowing density and cultivar effects on pith expression and yield in solid-stemmed durum wheat.", Agronomy Journal, 108(1), pp. 219-228. doi : 10.2134/agronj2015.0298 Access to full text
The wheat stem sawfly (WSS) (Cephus cinctus; Hymenoptera: Cephidae) is a destructive insect pest of spring, winter (Triticum aestivum L.), and durum wheat (Triticum turgidum L. var. durum) in North America. Sawfly larvae hatch from eggs deposited inside the stem, and their subsequent feeding damages vascular tissue, reducing photosynthetic capacity and grain yields. Growing solid-stemmed wheat cultivars that develop pith in the culm lumen is the most effective method to minimize yield losses. Recent work has focused on optimizing sowing densities to achieve maximum levels of pith expression and grain yields in common wheat; however, little research has been conducted on durum wheat. We investigated the influence of four sowing densities (150, 250, 350, 450 seeds m-2) on pith expression in two newly released solid-stemmed durum cultivars, CDC Fortitude and AAC Raymore, and compared them to the solid-stemmed common wheat cultivar, Lillian. CDC Fortitude and AAC Raymore displayed consistently high levels of pith expression across environments and sowing densities, in contrast to Lillian, which produced only slightly more pith than the hollow-stemmed durum check cultivar, Strongfield. A yield drag often associated with high pith expression was not evident as CDC Fortitude and AAC Raymore produced grain yield similar to Strongfield. When averaged over cultivars, increasing sowing density had a positive effect on grain yield, but was negatively associated with stem solidness. Our findings suggest that, unlike with CWRS solid-stemmed cultivars, altering sowing density is not required to achieve effective sawfly resistance with CDC Fortitude and AAC Raymore.
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