Inheritance of stem solidness and its relationship to yield and other agronomic traits in spring wheat
Hayat, Mohammad Aslam
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The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), a devastating pest of wheat, has caused considerable economic damage in the Pacific Northwest. Solid-stemmed wheat varieties have provided a genetic source of resistance against the insect. However, solid-stemmed wheats tend to yield less than hollow-stemmed wheats. Some, but not all, studies have shown yield to be negatively related to stem solidness. To date, it is not clear whether solid-stemmed wheats have low yield due to a negative genetic correlation or to the poor genetic background of the original solid-stemmed selections. The cause of the negative association between solid stems and other traits was studied in spring wheat using solid-stemmed wheats released in different eras. The progeny derived from different crosses between solid and hollow parents was evaluated to determine the genetic basis for improved yield in modern solid-stemmed spring wheats. Space-planted nurseries of different crosses grown in 1990 and 1991 showed that the genetic basis of stem solidness is different between an early release (Rescue) and a later release (Lew) Additionally, larger experiments of F6 progeny derived from crosses between solid and hollow parents were grown in two different environments and agronomic data were gathered. The genetic correlation coefficients between stem solidness and grain yield were small and did not tend to be negative. Therefore, no negative genetic relationship appears to exist between stem solidness and grain yield. However, stem solidness was found negatively correlated to protein and plant height in early solid-stemmed releases. Thus, it appears that a linkage existed between the genes for solid stems and genes conferring poor percent protein and tall plants in the early releases. This linkage appears to have been broken in later releases. Stem solidness was independent of all other traits studied. Heritabilities of all traits, except yield, were high.