SR9089 - Identify and Develop Strawberries Resistant to Tarnished Plant Bugs

Researcher:

Adam Dale, Dept. of Plant Agriculture, University of Guelph, Simcoe

Objectives:

1. To produce strawberry varieties that are tolerant of tarnished plant bug populations
   

2. To establish the relative tolerance of strawberry varieties and selections.
   

3. To make initial estimates of the heritablility of tarnished plant bug tolerance in strawberry.
   

4. To estimate the threshold of tolerance of 'Seascape' dayneutral strawberry.

Expected Benefits:

Reduced damage of the strawberry crop could lead to annual increases in returns to Ontario growers.

Summary of Research Results:

Initially, the relative tolerance of a large number of varieties and selections of both day-neutral and June-bearing types were studied. Two hundred different clones were set out in an experiment. These contained 95 named varieties and selections, 65 clones of the wild woodland strawberry, Fragaria virginiana, and 40 hybrids of the woodland strawberry with either varieties or the wild Chilean strawberry. These were planted out in twelve replicates of single plants of each clone and all the fruits produced were examined for tarnished plant bug damage for two years.

The wild woodland strawberries were found to be much more tolerant than the cultivated varieties and the hybrids were intermediate. When the variation within the different groups was examined, most of the wild clones had less than 15% damage whereas most of the varieties and selections had over 15% damage. The most tolerant clone (Eagle 2) was a wild woodland strawberry collected from the picnic area in Eagle, a small village just west of St. Thomas in southwestern Ontario. It had less than 1% damage in both years. A day-neutral variety, 'Fort Laramie' was identified which was much more tolerant than other day-neutral varieties. It had less than half the damage of the other day-neutrals.

The second stage was to hybridize the most tolerant day-neutral selections with other tolerant and susceptible clones to find out whether the tarnish plant bug tolerance could be successfully transferred to the next generation. Eleven families were made with various selections including the tolerant wild woodland strawberry 'Eagle2' and 'Fort Laramie'. To date we have only recorded fruit from the first year, but some exciting trends are being shown. All the individuals in the 'Eagle2' x 'Fern' (a dayneutral) family were highly tolerant and the 'Fort Laramie' families are consistently more tolerant than the other families with day-neutral parents.

Since the research has shown that strawberries can be very tolerant to tarnished plant bugs, the next question to be answered will be what is the mechanism of this tolerance. Researchers elsewhere have found that many flowers contain a chemical in their ovaries that make them unpalatable to feeding insects. After discussing this with my colleagues, we think that this could explain why tarnished plant bugs avoid some strawberry clones.

This research has clearly shown that some strawberries are less damaged by tarnished plant bugs and that it is possible to transfer this trait into day-neutral varieties with better horticultural characteristics. Eventually this will enable scientists to produce day-neutral strawberry varieties which are protected against this pest, and so enable a major barrier to expansion of the strawberry industry to be eliminated.