Field Evaluation of Screening Procedures for Thrips Resistance in Peanut

Abstract

Selection of an efficient, simple and accurate screening method is important in a varietal evaluation program. The objective of this study was to evaluate reactions of peanut lines to natural thrips infestation using thrips number parameters and thrips damage parameters to identify which parameters were consistent and most suitable in separating the difference of peanut lines. Another objective was to evaluate appropriate assessment times. A randomized complete block design with six replications was used at three environments. Data were recorded for adult thrips number. Juvenile thrips number, total thrips number, Percentage of damaged plants, percentage of damaged leaves and thrips damage rating at 30, 0, 0, 0 and 70 Days After Planting (DAP). Sticky traps were also used to monitor thrips abundance in environment 3 and found that Scirtothrips dorsalis was the most abundant species accounting for 48.7% of total adult thrips number. Differences among cultivars for adult thrips number and total thrips number were observed at 40, 0, 0 and 70 DAP, but not at 30 DAP. Differences among cultivars for juvenile thrips number were observed at 60 and 70 DAP. The differences among cultivars for thrips number were less consistent across evaluation dates. The most appropriate assessment times for thrips number would be between 50 to 70 DAP. It would be difficult to identify thrips resistant lines by using thrips number as selection criterion. Differences among cultivars for percentage of damaged plants were observed at 30, 0, 0 and 60 DAP, but not at 70 DAP. Appropriate assessment times would be at 30 to 50 DAP. Differences among cultivars for percentage of damaged leaves and thrips damage rating were quite similar and observed at 30 to 70 DAP. Appropriate assessment times would be at later evaluation dates (50 to 70 DAP). Plant damage parameters are more useful than thrips number in identifying differences among peanut cultivars. These parameters are more consistent across evaluation dates and years and should be promising for use as selection criteria for thrips resistance in peanut. Among tested cultivars, IC 10 showed the lowest thrips number and plant damage.