Development of a glasshouse bioassay suitable for evaluating Fusarium wilt resistance in strawberry

Fusarium wilt caused by Fusarium oxysporum f. sp. fragariae (Fof) causes significant losses to strawberry (Fragaria × ananassa) growers in Australia due to the rapid decline and death of affected plants. Use of cultivars with increased resistance to Fusarium wilt is an efficient strategy to reduce damage caused by this disease. This study addressed the need for an effective bioassay for the resistance breeding program for subtropical strawberry in south-east Queensland. Two conidial-suspension methods (root dip and injection) as well as three conidial concentrations within the root dip and two incubated seed-carrier (ryegrass and millet) inoculation methods were compared. Disease incidence and severity ratings were used to determine Fof infection and disease development. No significant differences were observed among conidial concentrations. Visual disease symptoms from seed-carrier methods (ryegrass and millet) were 2 weeks later than the root dip method. However, ryegrass inoculation is a very effective bioassay method that produced a significantly higher disease rating than the other treatments, was easy to administer, and required fewer resources and less labour.