Soybean Cyst Nematodes Influence Aboveground Plant Volatile Signals Prior to Symptom Development

Abstract

Soybean cyst nematode (SCN), Heterodera glycines, is one of the most destructive soybean pests worldwide. Unlike many diseases, SCN doesn't show above ground evidence of disease until several weeks after infestation. Knowledge of Volatile Organic Compounds (VOCs) related to pests and pathogens of foliar tissue is extensive, however, information related to above ground VOCs in response to root damage is lacking. In temporal studies, gas chromatography-mass spectrometry analysis of VOCs from the foliar tissues of SCN infested plants yielded 107 VOCs, referred to as Common Plant Volatiles (CPVs), 33 with confirmed identities. Plants showed no significant stunting until 10 days after infestation. Total CPVs increased over time and were significantly higher from SCN infested plants compared to mock infested plants post 7 days after infestation (DAI). Hierarchical clustering analysis of expression ratios (SCN: Mock) across all time points revealed 5 groups, with the largest group containing VOCs elevated in response to SCN infestation. Linear projection of Principal Component Analysis clearly separated SCN infested from mock infested plants at time points 5, 7, 10 and 14 DAI. Elevated Styrene (CPV11), D-Limonene (CPV32), Tetradecane (CPV65), 2,6-Di-T-butyl-4-methylene-2,5-cyclohexadiene-1-one (CPV74), Butylated Hydroxytoluene (CPV76) and suppressed Ethylhexyl benzoate (CPV87) levels, were associated with SCN infestation prior to stunting. Our findings demonstrate that SCN infestation elevates the release of certain VOCs from foliage and that some are evident prior to symptom development. VOCs associated with SCN infestations prior to symptom development may be valuable for innovative diagnostic approaches.

Biochemical analysis of the TPS-a subfamily in Medicago truncatula

“…Soybean terpene synthases Gm TPS3, Gm TPS18 and Gm TPS21 have been characterized and shown to produce β-ocimene, geraniol and α-farnesene respectively, each of which have demonstrated protective roles in plants ( Liu et al., 2014 ; Lin et al., 2017 ; Han et al., 2023 ). For example, Gm TPS21 (which encodes for α-farnesene) provided resistance against soybean cyst nematode belowground and aphids aboveground ( Lin et al., 2017 ; Constantino et al., 2021 ). In cowpea, terpenes were identified as part of the volatiles produced in response to herbivory whereas biochemical characterization of the genes responsible for floral scent was carried out in sweet pea ( Bao et al., 2020 ; Steinbrenner et al., 2022 ).…”