**Yield response to treatment with vesicular-arbuscular myccorrhiza
(VAM) in a breeding population of barley**

**Mario C. Therrien**

Agriculture and Agri-Food Canada, Brandon Research Centre, Box 1000A,
R.R.#3, Brandon, MB, Canada, R7A 5Y3, <mtherrien@agr.gc.ca>

**Abstract**

Vesicular-arbuscular myccorrhiza (VAM; *Glomus* spp.) are soil fungi
that can colonize the roots of a number of commercially important crops,
including barley, and are implicated in increasing the availability of
nutrients to the host plant, particularly phosphorus (P). This has been
shown to increase yields in the host crop. Barley has shown a
differential response to increased yield after inoculation with VAM
culture. Two barley cultivars with differential yield response to VAM
treatment, Virden and CDC Earl, were crossed and 200 Recombinant Inbred
Lines (RILs) were produced. Seeds of individual heads, from the parents
and RILs, were treated with VAM or left untreated and planted as head
rows in a Completely Randomized Design (CRD) in a soil low in nutrients
and nearly devoid of native VAM. Grain and dry matter yield response
indicated that VAM treatment produced a significant yield increase in
CDC Earl and significant yield suppression in Virden. VAM-treated RILs
demonstrated significant yield suppression, indicating that genetic
improvement for this trait is unlikely in barley.

**Introduction**

Vesicular-arbuscular myccorrhiza (VAM; *Glomus* spp.) are fungi that can
colonize the roots of a number of important crops, including barley
(*Hordeum vulgare* L.) and provide benefits to the host plant by
mobilizing nutrients from the soil, especially phosphorus (P; Jensen,
1982). The effectiveness of VAM has been demonstrated in the field for a
number of crops (Jensen, 1984). This has led to the availability of
commercial inoculants of VAM for field use (Bagyaraj, 1991). In barley,
colonization by VAM appears to be at least partially dependent on
genotype where some genotypes demonstrate enhanced biomass and grain
yield while others do not (Boyetchko and Tewari, 1995). Developing new
barley cultivars, with the ability to increase yield with VAM
inoculation, would be advantageous to producers. This study utilizes a
breeding population of barley, developed from two genotypes with
positive and negative response to VAM inoculation, to determine the
feasibility of breeding for improved VAM-mediated yield response in
barley.

**Materials and Methods**

Using Virden (VAM-negative response) and CDC Earl (VAM-positive
response) six-row barley cultivars, 300 manual crosses were made
yielding 220 F1 seeds. Each F1 seed was then placed through four cycles
of Single Seed Descent (SSD) producing a total of 220 Recombinant Inbred
Lines (RILs). Remnant seed of the original parent material was also
saved and multiplied along with the RILs. The 220 RILs were grown in
single 3 m long rows, along with twenty four rows of each of the two
parents. Three heads were selected, at random, from each row and
individually manually threshed and stored in labelled envelopes. One
half of the RILs and parent seed were treated with a commercial inoculum
of vesicular-arbuscular micchoryza (VAM; Mikro-VAM®) according to
manufacturer specifications (Mikro-Tek Inc., Timmons, ON, Canada). The
remaining half were left untreated as served as the control group.

Each package of seed was sown in individual head rows in a Completely
Randomized Design (CRD) and each row labelled accordingly. Head rows
were sown on a medium-textured clay loam soil that had been deliberately
sown to canola in the three previous crop years to eliminate most of the
native VAM and reduce nitrogen (N) and phosphorus (P) levels to 30 and
20 kg ha^-1^, respectively. Sixty kg ha^-1^ N, as urea, was added to the
soil, prior to sowing, to allow for normal crop development. Potassium
(K) was not limiting in this soil, being in excess of 300 kg ha^-1^ of
native K. Levels of P were not augmented to allow for the expression of
VAM activity in a low P soil.

Head rows were allowed to mature completely prior to the entire plants
above-ground being harvested by hand. Entire rows were individually
weighed, to the nearest 0.5 g, to obtain dry matter yield per row. Each
row was then threshed in a stationary plot combine and the subsequent
seed collected and weighed to the nearest 0.5 g. to obtain grain yield
per row. An Analysis of Variance (ANOVA) was performed for both grain
and dry matter yield using the PROC GLM of SAS (SAS Institute, 1988).

**Results and Conclusions**

The parent cultivars, CDC Earl and Virden, were chosen because they
demonstrated differential responses to VAM treatment (Boyetchko &
Tewari, 1995), with CDC Earl demonstrating a positive response and
Virden having no, or a negative, response. The parent cultivars, Virden
and CDC Earl, gave yield responses to VAM treatment that were expected.
CDC Earl showed an increase in both dry matter yield (Table 1) and grain
yield (Table 2) after treatment with VAM, whereas Virden showed reduced
dry matter yield (Table 1) and a slight reduction (non-significant) in
grain yield (Table 2).

The yield values for the RILs were intermediate to the parents (Tables 1
and 2), as would be expected for the quantitative traits of grain and
dry matter yield. For dry matter yield, the RILs showed a response
similar to Virden, which was a decrease in yield, albeit non-significant
(Table 1). For grain yield, the RILs showed only a slight
(non-significant) increase in yield (Table 2), with values closer to
Virden than to CDC Earl. The results suggest that there would be no
genetic improvement from a cross between these VAM responsive and
non-responsive genotypes. Further evaluation with multiple genotypes may
provide genetic gain for yield from VAM inoculation via recombination
from genetic backgrounds differing from those in the present study.

  -------------- ------------- ---------------- ------------ ------------------ --------------
  Table 1.                                                                      
  Average dry                                                                   
  matter yield                                                                  
  (g plot^-1^)                                                                  
  of inoculated                                                                 
  vs.                                                                           
  uninoculated                                                                  
  (control)                                                                     
  Virden, CDC                                                                   
  Earl and RILs                                                                 
  treated with                                                                  
  VAM.                                                                          

  **Source**     **Control**   **Inoculated**   **Standard   **Significance**   **Response**
                                                Error**                         

  CDC Earl       399.1         435.5            16.1         \*\*               Increase

  Virden         516.5         469.4            27.3         \*                 Decrease

  RILs           450.1         436.7            19.0         ns                 Decrease

  Average        455.2         447.2                                            

  Std. Error     34.0          11.1                                             

  CV             7.5           2.5                                              
  -------------- ------------- ---------------- ------------ ------------------ --------------

  -------------- ------------- ---------------- ------------ ------------------ --------------
  Table 2.                                                                      
  Average grain                                                                 
  yield (g                                                                      
  plot^-1^) of                                                                  
  inoculated vs.                                                                
  uninoculated                                                                  
  (control)                                                                     
  Virden, CDC                                                                   
  Earl and RILs                                                                 
  treated with                                                                  
  VAM.                                                                          

  **Source**     **Control**   **Inoculated**   **Standard   **Significance**   **Response**
                                                Error**                         

  CDC Earl       128.2         140.8            6.1          \*\*               Increase

  Virden         97.8          97.6             8.5          ns                 No change

  RILs           117.4         119.6            4.3          ns                 Increase

  Average        114.5         119.3                                            

  Std. Error     8.9           12.5                                             

  CV             7.8           10.5                                             
  -------------- ------------- ---------------- ------------ ------------------ --------------

**Acknowledgements**

The author is grateful to Dr. R.B. Irvine for suggesting the topic and
to Dr. R. Mohr for providing the plot land.

**References**

Bagyaraj, D.J. 1991. Ecology of vesicular-arbuscular mycchorizae. In:
Handbook of Applied Mycology: Soil and Plants (Eds. D.K. Arola, R. Rai,
K.G. Mukerjii and G.R. Knudsen) pp. 3-34. Marcel Dekker, New York, USA.

Boyetchko, S.M. and J.P. Tewari. 1995. Susceptibility of barley
cultivars to vesicular-arbuscular mycorrhizal fungi. Can. J. Plant Sci.
75(1): 269-275.

Jensen, A. 1982. Influence of four vescicular-arbuscular micorrhyzal
fungi on nutrient uptake and growth in barley. New Phytol. 90: 45-50.

Jensen, A. 1984. Response of barley, pea and maize to inoculation with
different vesicular-arbuscular mycchorizal fungi in irradiated soil.
Plant and Soil 78(3): 315-323.

SAS Institute. 1988. SAS user's guide: Statistics. Version 6.04 ed., SAS
Inst., Cary, NC.