The combined impacts of wheat spatial position and phenology on cereal aphid abundance

Abstract

Background Wheat is a staple crop that suffers from massive yield losses caused by cereal aphids. Many factors can determine the abundance of cereal aphids and the damage they cause to plants; among them are the plant’s genetic background, as well as environmental conditions such as spatial position within the plot, the composition and the distance from neighboring vegetation. Although the effects of these factors have been under scrutiny for many years, the combined effect of both factors on aphid populations is not fully understood. The goal of this study was to examine the collective impact of genotype and environment on wheat phenology (developmental stages), chemical diversity (metabolites), and insect susceptibility, as manifested by cereal aphid abundance. Methods To determine the influence of plant genotype on the metrics mentioned above, we measured the phenology, chemical profile, and aphid abundance of four wheat genotypes, including the tetraploid wild emmer (Triticum turgidum ssp. dicoccoides cv. Zavitan), tetraploid durum (Triticum turgidum ssp. durum cv. Svevo), and two hexaploid spring bread (Triticum aestivum), ‘Rotem’ and ‘Chinese Spring’. These genotypes are referred to as “focal” plants. To evaluate the impact of the environment, we scored the distance of each focal plant (spatial position) from two neighboring vegetation types: (i) natural resource and (ii) monoculture wheat resource. Results The results demonstrated that the wild emmer wheat was the most aphid-resistant, while the bread wheat Rotem was most aphid-susceptible. Aphids were more abundant in plants that matured early. The spatial position analysis demonstrated that aphids were more abundant in focal plants located closer to the margin monoculture wheat resource rather than to the natural resource, suggesting a resource concentration effect. The analysis of metabolic diversity showed that the levels of three specialized metabolites from the flavonoid class, differed between the wheat genotypes and some minor changes in central metabolites were shown as well. Altogether, these results demonstrate a combined effect of genetic background and spatial position on wheat phenology and aphid abundance on plants. This exposes the potential role of the marginal vegetation environment in shaping the insect population of desirable crops. These findings highlight the importance of maintaining plant intra-specific variation in the agriculture system because of its potential applications in reducing pest density.

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

“…In the late stages of leaf development, when the formation of the epidermis is completed, trichomes’ functional roles become less important, and leaves often senesce and shed ( Valkama et al, 2004 ). Notably, in our recent reports, we compared the aphid resistance of wheat genotypes in a lab-controlled growth room, counting aphid reproduction after 96 h on wheat seedlings ( Batyrshina et al, 2020b ), with an evaluation of the natural aphid population on 3-month-old plants grown in the field ( Batyrshina et al, 2020a ). We found the opposite trends between the two growth conditions, where Svevo was more resistant in the lab conditions and more susceptible in the field versus the WEW accession, Zavitan.…”

“…Constitutive defense mechanisms are present in plant tissues as anticipatory strategies in preparation for forthcoming adverse conditions (Mertens et al, 2021). Defense mechanisms can also be dynamic and induced upon herbivore attack, depending on plant age, developmental stage, and genetic background (Howe and Jander, 2008;Brunissen et al, 2009;Chandrasekhar et al, 2018;Batyrshina et al, 2020a). Variation in these mechanisms at the spatial level (individual parts within a plant) may be one of the key determinants of pest reproduction and feeding behavior (Awmack and Leather, 2002;Karley et al, 2002;Jakobs and Müller, 2018).…”

“…The phloem cell’s architecture provides an additional line of defense in terms of mechanical barriers, owing to latex exudation, resin, or callose deposition around the sieve elements ( Ahmad et al, 2011 ). The interaction between the aphid and the host plant involves the coordinated reconfiguration of metabolism, which is regulated by developmental, genetic, and environmental inputs ( Kooke and Keurentjes, 2011 ; Batyrshina et al, 2020a ). Many defensive compounds, such as glucosinolates, terpenes, and BXDs, have been detected in phloem sap ( Chen et al, 2001 ), which may be particularly effective against aphids and other phloem-feeding insects.…”

Chemodiversity affects preference forTanacetum vulgarechemotypes in two aphid species

“…Various studies point out that traits related to growth or to structural defenses may play an important role in driving interactions between plants and insects (Herms & Mattson 1992; Agrawal & Fischbein 2006). For instance, in a study on wheat plants, Batyrshina et al (2020) found higher numbers of aphids on fast-maturing than on slow-maturing wheat plants, and trade-offs between plant growth and defense are common in nature (Coley et al 1985; Herms & Mattson 1992). Furthermore, plants with stronger mechanical defenses tend to be better defended against insect herbivory (Caldwell, Read & Samson 2015).…”

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

“…Water was provided once a week, either via rainfall or irrigation. Fertilizer was provided as previously described ( Batyrshina et al, 2020a ), and no pesticides or herbicides were applied during the experiments. The Revadim experimental site included a total of 21 accessions sown in a randomized block design with four replicates.…”