Characterization of Resistance to Cephus cinctus (Hymenoptera: Cephidae) in Barley Germplasm

Abstract

Most barley cultivars have some degree of resistance to the wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae). Damage caused by WSS is currently observed in fields of barley grown in the Northern Great Plains, but the impact of WSS damage among cultivars due to genetic differences within the barley germplasm is not known. Specifically, little is known about the mechanisms underlying WSS resistance in barley. We characterized WSS resistance in a subset of the spring barley CAP (Coordinated Agricultural Project) germplasm panel containing 193 current and historically important breeding lines from six North American breeding programs. Panel lines were grown in WSS infested fields for two consecutive years. Lines were characterized for stem solidness, stem cutting, WSS infestation (antixenosis), larval mortality (antibiosis), and parasitism (indirect plant defense). Variation in resistance to WSS in barley was compared to observations made for solid-stemmed resistant and hollow-stemmed susceptible wheat lines. Results indicate that both antibiosis and antixenosis are involved in the resistance of barley to the WSS, but antibiosis seems to be more prevalent. Almost all of the barley lines had greater larval mortality than the hollow-stemmed wheat lines, and only a few barley lines had mortality as low as that observed in the solid-stemmed wheat line. Since barley lines lack solid stems, it is apparent that barley has a different form of antibiosis. Our results provide information for use of barley in rotation to control the WSS and may provide a basis for identification of new approaches for improving WSS resistance in wheat.

Multiple decrement life tables of Cephus cinctus Norton (Hymenoptera: Cephidae) across a set of barley cultivars: The importance of plant defense versus cannibalism

“…By consuming conspecific larvae, H. axyridis avoids the potential negative effect of plant toxins [53]. Several previous reports [4,54] and the current study have indicated that a large proportion of C. cinctus neonate mortality indicates that either the host stem tissues contain antibiotic toxins, or possibly the tissues lack some essential nutrients required for neonate growth and development (categorized as plant defense: Table 2, Fig 2). But by consuming conspecific larvae and eggs, first, each cannibal avoids both tissue toxins or diet deficiency and acquires additional nutrient resources.…”

“…Wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), successfully adapted from its ancestral wild grass hosts to domesticated spring and winter wheat cultivars [1]. In addition, this species is not only widening its range southward to Colorado and Kansas [2], but it also is increasing infestation and larval survival in barley in Montana [3,4]. To mitigate economic loss, an integrated pest management (IPM) approach has been recommended for wheat across the northern Great Plains [5].…”

“…Although barley was historically categorized as resistant to C. cinctus, a decade-long study revealed an increasing infestation rate and larval survival rate of C. cinctus in barley in Montana [4]. Montana ranked second among barley producing states based on the amount of production in the US in 2019 [15].…”

Plant defense elicitors: plant fitness versus wheat stem sawfly

“…Annual economic loss caused by Cephus cinctus damage to wheat is estimated to be $100–350 million in the USA and Canada ( Beres et al, 2011 ). In addition, WSS also damages barley ( Hordeum vulgare L.) and rye ( Secale cereal L.) ( Wallace & McNeal, 1966 ; Beres et al, 2011 ; Varella et al, 2018 ).…”

Genome sequence of the wheat stem sawfly, Cephus cinctus, a primitive hymenopteran and wheat pest, illuminates evolution of hymenopteran chemoreceptors

“…The wheat stem sawfly, Cephus cinctus Norton, is a major pest of wheat in western North America with a southward expanding geographic range likely driven by localized adaptation to cultivated crops from surrounding wildlands (Beres et al 2011;Lesieur et al 2016;Adhikari et al 2018;Varella et al 2018). It is a native species that also uses many other grass hosts and hence plays an important role in the ecology of grasslands (Cockrell et al 2017).…”