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

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.

Comparative transcriptomic and metabolic analysis of wild and domesticated wheat genotypes reveals differences in chemical and physical defense responses against aphids

“…This discordance may arise from accession-specific differences or may be due to the experiment being performed on mature wheat plants in field conditions, compared to young seedlings under controlled conditions (Additional file 2: Figure S1). This was supported by another study that suggests that the differences in aphid preference depend on the plant's developmental stage in the field, compared to seedlings in the laboratory [79].…”

Defence gene expression and phloem quality contribute to mesophyll and phloem resistance to aphids in wild barley

“…Screening crop wild relatives for (partial-)resistance against aphids provides an opportunity to identify potentially beneficial traits (Zhang et al, 2017) for introduction into agricultural cultivars (Xu et al, 2015;Li et al, 2018;Arora et al, 2019). Screening of wild relatives in wheat (Xu et al, 2015;Aradottir et al, 2017) and maize (Maag et al, 2015) has identified partial-resistance traits associated with reduced palatability and elevated levels of secondary metabolites (Barria et al, 1992;Ahmad et al, 2011;Greenslade et al, 2016;Chandrasekhar et al, 2018;Li et al, 2018). In crops such as wheat, maize, potato, and tomato, partial-resistance has been associated with both singular and interacting epidermal-mesophyll-and phloem-based resistance factors (Alvarez et al, 2006;Greenslade et al, 2016;Machado-Assefh and Alvarez, 2018).…”

Comparative transcriptomic and metabolic analysis of wild and domesticated wheat genotypes reveals differences in chemical and physical defense responses against aphids

“…This discordance may arise from accessionspecific differences or may be due to the experiment being performed on mature wheat plants in field conditions, compared to young seedlings under controlled conditions ( Figure S1). This was supported by another study that suggests that the differences in aphid preference depend on the plant's developmental stage in the field, compared to seedlings in the laboratory [79].…”