Presentation: Inheritance of the Semi-Dwarf Trait in Barley

Introduction

The semi-dwarf trait, when associated with superior straw-strength, is important for yield stability in the high rainfall areas of barley production where yields often exceed 6.5 t ha^-1. However, the association of reduced stature with short heads may limit yield potential.

Purpose

The purpose of this project was to determine if cultivars and introductions grown in western Canada had different semi-dwarf genes and the association of these genes with head length (yield component) and stem diameter (lodging).

Materials and Methods

• Twenty crosses were made between 2 standard height cultivars and 7 semi-dwarf cultivars and advanced lines.
• The F₁ generation was grown at the Field Crop Development Centre, Lacombe, Alberta, Canada.

• In the winter of 1991-92, approximately 200 spaced plants of the F2 generation were grown at the University of California Research Station at El Centro, CA.
• Confidence intervals (CI) at 90% were calculated for height of the parental lines and used to determine five classes:
  TS - shorter than the shorter parent
  SP - same as the shorter parent
  I - intermediate to the parents
  TP - same as the taller parent
  TT - taller than the taller parent
  

  
  Taking head length measurements

  
  Taking height measurements

  
  Using calipers to measure top culm diameter (top and bottom culm diameters had been found to be highly correlated in an earlier report)

Height

• Distribution of the F2’s in the five height classes is summarized in Figures 1 to 4.
• In the semi-dwarf x standard height crosses, 2 to 3 genes could account for most height differences.
• The semi-dwarf x semi-dwarf crosses all segregated for transgressive short and tall plants in the F2 which indicated that these lines had different semi-dwarf genes. At the time of this study, we did not have crosses between Duke, Samson and Winchester so were unable to determine if these three semi-dwarfs had different genes. These crosses were made at a later date and grown in California in 1995 (see Addendum).
• Crosses of I80047 and I83022 to Leduc (a standard height cultivar) segregated in a 3-gene ratio.
• Due to the lack of transgressive hills, Leduc may have a gene for height in common with these introductions.
• Crosses of these two introductory lines to Duke, Samson and Winchester segregated in 2-gene ratios. Therefore, although these cultivars/lines may have a height gene in common, they have different semi-dwarf genes.

Figure 2. Distribution of Height Classes in the F2 Generation (5 Crosses) Grown in California in 1991-1992.

Figure 3. Distribution of Height Classes in the F2 Generation (6 Crosses) Grown in California in 1991-1992.

Figure 4. Distribution of Height Classes in the F2 Generation (4 Crosses) Grown in California in 1991-1992.

Head length

• Highly significant positive correlations of head length with height were found for all but two crosses.
• In one of these crosses, I83022 x Duke, the lack of association may have been due to the similarity in height of the two parents. In the other cross, Samson x Noble, the lack of association may have been due to the semi-dwarf having a longer head than the standard height cultivar.

• In 4 of 8 crosses where top internode diameters were measured, no significant correlations with height were found.

• Based on transgressive segregation, we conclude that the semi-dwarf cultivars/lines used in this study possessed different semi-dwarf genes.
• Most of the semi-dwarfs have 2 or 3 independently segregating genes.
• Head length was strongly correlated with height but the correlation was not absolute; selection of long heads in a semi-dwarf line will require strong selection pressure.
• In those crosses where there was no significant correlation between top internode diameter and height, selection for lodging resistance due to wide stem diameter will require independent selection from height.
• Where short stature was significantly correlated with wide stem diameter, lodging resistance will be indirectly selected by selection for plant height.

• Samson x Duke cross: There were 3 major genes in this cross. As well, there was probably one gene in common, as there were no transgressive tall segregants.
• Samson x Winchester cross: The absence of TS segregants indicate Samson and Winchester have the same semi-dwarf genes. We were unsure if the TT found was a segregant or a contaminant.
• Duke and Winchester were taller than Samson and had longer spikes; for both crosses, spike length was positively correlated with height. Stem diameter was not significantly correlated with height in these two crosses.

J.H. Helm, P.E. Juskiw, M.J. Cortez
Field Crop Development Centre

Presented at the 8th International Barley Genetics Symposium, Adelaide, South Australia, October 22-27, 2000