Antixenosis, antibiosis, and potential yield compensatory responses in barley cultivars exposed to wheat stem sawfly (Hymenoptera: Cephidae) under field conditions

Authors: ACHHAMI, BUDDHI - Montana State University; Reddy, Gadi V.P.; SHERMAN, JAMIE - Montana State University; PETERSON, ROBERT - Montana State University; WEAVER, DAVID - Montana State University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2020
Publication Date: 9/22/2020
Citation: Achhami, B.B., Reddy, G.V., Sherman, J.D., Peterson, R.K., Weaver, D.K. 2020. Antixenosis, antibiosis, and potential yield compensatory responses in barley cultivars exposed to wheat stem sawfly (Hymenoptera: Cephidae) under field conditions. Journal of Insect Science. 20(5):1-14. https://doi.org/10.1093/jisesa/ieaa091.
DOI: https://doi.org/10.1093/jisesa/ieaa091

Interpretive Summary: We aimed to explore antixenosis that determines wheat steam sawfly host selection behavior and oviposition and antibiosis that reflects larval mortality and the number of nodes injured by feeding in barley varieties. We measured potential yield compensation that could indicate a variation in responses to larval feeding injuries. The results indicated that in barley cultivars show varying levels of antixenosis, antibiosis, and potential yield compensation traits that prepare a foundation to understand the specificity of host plant interactions. Knowledge of these interactions can be advanced by conducting transcriptomic, proteomic, and metabolomic studies that can help to decipher key resistance pathways in these cultivars. After doing these, we can better incorporate the selected traits for developing novel barley cultivars, and possibly other cereal grain cultivars, with greater resistance to wheat stem sawfly. This study will provide an understanding of these key types of host plant resistance in different barley classes, which should be the foundation of an integrated pest management strategy.

Technical Abstract: Wheat stem sawfly, Cephus cinctus Norton (Hymenoptera), females require favorable host cues to locate and oviposit in host plants. Larvae of C. cinctus injure the host plant by feeding inside the stem and by girdling the base of ripened stems before obligate diapause. Barley, Hordeum vulgare L. (Gramineae), cultivars were previously planted as resistant crops in rotations to manage C. cinctus, but due to increasing levels of injury in crop fields this is no longer a valid management tactic in Montana. Therefore, we aimed to understand antixenosis (behavioral preference), antibiosis (mortality), and potential yield compensation (increased productivity in response to stem injuries) in barley exposed to C. cinctus. We examined these resistance traits in eight barley cultivars spanning malt, forage, and feed classes. Antixenosis was assessed by counting the number of eggs per stem and antibiosis was assessed by counting infested stems, dead larvae, and stems cut by mature larvae. Potential yield compensation was evaluated by comparing grain yield from three categories of stem infestation: 1) uninfested, 2) infested but the larva died, and 3) infested with a surviving larva that cut the ripened stem at crop maturity. We found the greatest number of eggs per infested stem (1.80 ± 0.04), the highest proportion of infested stems (0.63 ± 0.01), the lowest proportion of dead larvae (0.31 ± 0.01), and the highest proportion of cut stems (0.33 ± 0.01) in the malt cultivar ‘Hockett’. This popular cultivar, by production acreage, was highly attractive to C. cinctus females, and subsequent larval mortality in ‘Hockett’ stems was lower than for other cultivars planted. Seven out of eight cultivars had greater grain weight for infested stems than for uninfested stems. These cultivars may have compensatory responses to larval feeding injury, but it is difficult to separate this from preference for larger stems by ovipositing females. Overall, these barley cultivars contain varying levels of antixenosis to adult females, varying antibiosis to feeding larvae, and different yield compensation patterns in response to larval feeding injuries. Our results provide a foundation of knowledge to explore resistance cues in barley and subsequently provide a framework to further develop C. cinctus resistant or tolerant barley cultivars.