Variation Between Three Eragrostis tef Accessions in Defense Responses to Rhopalosiphum padi Aphid Infestation

Abstract

Tef (Eragrostis tef), a staple crop that originated in the Horn of Africa, has been introduced to multiple countries over the last several decades. Crop cultivation in new geographic regions raises questions regarding the molecular basis for biotic stress responses. In this study, we aimed to classify the insect abundance on tef crop in Israel, and to elucidate its chemical and physical defense mechanisms in response to insect feeding. To discover the main pests of tef in the Mediterranean climate, we conducted an insect field survey on three selected accessions named RTC-144, RTC-405, and RTC-406, and discovered that the most abundant insect order is Hemiptera. We compared the differences in Rhopalosiphum padi (Hemiptera; Aphididae) aphid performance, preference, and feeding behavior between the three accessions. While the number of aphid progeny was lower on RTC-406 than on the other two, the aphid olfactory assay indicated that the aphids tended to be repelled from the RTC-144 accession. To highlight the variation in defense responses, we investigated the physical and chemical mechanisms. As a physical barrier, the density of non-granular trichomes was evaluated, in which a higher number of trichomes on the RTC-406 than on the other accessions was observed. This was negatively correlated with aphid performance. To determine chemical responses, the volatile and central metabolite profiles were measured upon aphid attack for 4 days. The volatile analysis exposed a rich and dynamic metabolic profile, and the central metabolism profile indicated that tef plants adjust their sugars and organic and amino acid levels. Overall, we found that the tef plants possess similar defense responses as other Poaceae family species, while the non-volatile deterrent compounds are yet to be characterized. A transcriptomic time-series analysis of a selected accession RTC-144 infested with aphids revealed a massive alteration of genes related to specialized metabolism that potentially synthesize non-volatile toxic compounds. This is the first report to reveal the variation in the defense mechanisms of tef plants. These findings can facilitate the discovery of insect-resistance genes leading to enhanced yield in tef and other cereal crops.

The Effectiveness of Physical and Chemical Defense Responses of Wild Emmer Wheat Against Aphids Depends on Leaf Position and Genotype

“…Different waveform patterns, in which the aphid is engaged in different activities, were identified according to previously described categories ( Tjallingii, 1978 ; Tjallingii and Esch Hogen, 1993 ). Due to the large number of experimental groups (two leaves from three accessions), aphid behavior was recorded for 3 h to capture only the initial events of significant feeding differences among the accessions ( Gyan et al, 2020 ). Three main phases were analyzed, including (i) epidermis: time until the first probing (t_1Pr), (ii) the total duration of C (s_C), and (iii) the total duration in the phloem E (s_E), which includes phloem salivation (E1) followed by phloem ingestion E2 (s_E1–>E2).…”

“…Glandular trichomes are used for exudate storage and secretion, while non-glandular trichomes, specialized epidermal hair-like structures, may affect aphid movement and reproduction rates ( Riddick and Simmons, 2014 ). The leaf surface of young wheat, barley ( Hordeum vulgare ), and tef ( Eragrostis tef ) plants are covered with non-glandular trichomes ( Leybourne et al, 2019 ; de Correa et al, 2020 ; Gyan et al, 2020 ). Trichome-based insect resistance is distributed unevenly across plants, tissues, and organs.…”

Identification of azukisapogenol triterpenoid saponins from Oxytropis hirta Bunge and their aphicidal activities against pea aphid Acyrthosiphon pisum Harris

“…The active saponins 4 – 7 were evaluated for their effects on the reproduction of the adult A. pisum aphids using a reference method with a little modification 40 . A number of healthy pea aphids, which could give birth normally, were selected and reared on faba bean plants.…”

“…The active saponins 4-7 were evaluated for their effects on the reproduction of the adult A. pisum aphids using a reference method with a little modification. 40 A number of healthy pea aphids, which could give birth normally, were selected and reared on faba bean plants. The adult aphids were removed after 24 h. The newborn aphids experienced 7 days from nymph to adult, and another 2 days to possess reproductive abilities were selected for the bioassay.…”

Value of teff (Eragrostis tef) genetic resources to support breeding for conventional and smallholder farming: a review

“…Its Page 2 of 16 Woldeyohannes et al CABI Agriculture and Bioscience (2022) 3:27 current average productivity is well below its genetic potential: improved cropping technologies in non-lodging conditions can result in yields exceeding 4.5 t ha −1 (Tefera and Ketema 2001), more than double the national average (Central Statistical Agency 2018). However, teff yield potential can be fully achieved only when applying appropriate sowing and plant curation (Ben-Zeev et al 2020;Mihretie et al 2021;Bogale et al 2013), management of soil fertility (Wato 2019), and appropriate agronomic practices (Gezahegn et al 2019;Berhe et al 2013) including weed management (Rezene and Zerhun 2000) and pest management (Gemechu Degete 2021;Gyan et al 2020).…”