Searching for wheat resistance to aphids and wheat bulb fly in the historical Watkins and Gediflux wheat collections.

G.I Aradottir,J.A Pickett,J.L Martin,L.E Smart,S.J Clark

doi:10.1111/aab.12326

Abstract

Insect pests can reduce wheat yield by direct feeding and transmission of plant viruses. Here we report results from laboratory and field phenotyping studies on a wide range of wheat, including landraces from the Watkins collection deriving from before the green revolution, more modern cultivars from the Gediflux collection (north‐western Europe) and modern UK Elite varieties, for resistance to the bird cherry‐oat aphid, Rhopalosiphum padi (Homoptera: Aphididae) and the English grain aphid, Sitobion avenae (Homoptera: Aphididae). A total of 338 lines were screened for R. padi and 340 lines for S. avenae. Field trials were also conducted on 122 Watkins lines to identify wheat bulb fly, Delia coarctata, preference on these landraces. Considerable variation was shown in insect performance among and within different wheat collections, with reduced susceptibility in a number of varieties, but phenotyping did not identify strong resistance to aphids or wheat bulb fly. Field trials showed within collection differences in aphid performance, with fewer aphids populating lines from the Watkins collection. This differs from development data in laboratory bioassays and suggests that there is a pre‐alighting cue deterring aphid settlement and demonstrates differences in aphid preference and performance on older plants in the field compared with seedlings in the laboratory, highlighting the need for phenotyping for aphid resistance at different plant growth stages. No association was identified between performance of the different insect species on individual varieties, potentially suggesting different nutritional requirements or resistance mechanisms.

Highlights

Wheat, Triticum aestivum L., is the third most important cereal crop in the world and the dominant crop for human consumption in temperate countries
A considerably larger number of lines were available to be tested from the Watkins collection, where out of 275 accessions, 22 showed increased R. padi nymph weight gain compared with Solstice and none showed a lower R. padi nymph weight
There were fewer accessions that showed a difference in weight for S. avenae nymphs, with just two for each of the Gediflux and Watkins collections, both showing a lower nymph weight gain compared with Solstice

Summary

Introduction

Triticum aestivum L., is the third most important cereal crop in the world and the dominant crop for human consumption in temperate countries. The global wheat production forecast for 2014 is 718.5 million tonnes globally, with Europe and UK contributions estimated at 236.3 and 16.6 million tonnes, respectively. Protection of wheat yield is of both economic and social importance and this must include preventing loss of yield to insect pests. Several aphid species are economically important pests of wheat including the bird cherry–oat aphid, Rhopalosiphum padi (L.) (Homoptera: Aphididae) and the grain aphid, Sitobion avenae F. Aphid damage to crops is controlled mainly by insecticidal treatments (Tanguy & Dedryver, 2009). This is failing, as a result of the evolution of insecticide resistance, with some species exhibiting resistance to multiple insecticidal classes (Bass et al, 2014). This, coupled with restrictions on the use of some pesticides in Europe, has focused global research efforts to find alternatives to pesticides (Loxdale, 2008; Sparks, 2013)

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