Seedling growth and fall armyworm feeding preference influenced by dhurrin production in sorghum

Shelby M Gruss,Manoj Ghaste,Joshua R Widhalm,Mitchell R Tuinstra

doi:10.1007/s00122-021-04017-4

Shelby M Gruss, Manoj Ghaste + Show 2 more

Open Access

https://doi.org/10.1007/s00122-021-04017-4

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Abstract

Cyanogenic glucosides (CGs) play a key role in host-plant defense to insect feeding; however, the metabolic tradeoffs between synthesis of CGs and plant growth are not well understood. In this study, genetic mutants coupled with nondestructive phenotyping techniques were used to study the impact of the CG dhurrin on fall armyworm [Spodoptera frugiperda (J.E. Smith)] (FAW) feeding and plant growth in sorghum [Sorghum bicolor (L.) Moench]. A genetic mutation in CYP79A1 gene that disrupts dhurrin biosynthesis was used to develop sets of near-isogenic lines (NILs) with contrasting dhurrin contents in the Tx623 bmr6 genetic background. The NILs were evaluated for differences in plant growth and FAW feeding damage in replicated greenhouse and field trials. Greenhouse studies showed that dhurrin-free Tx623 bmr6 cyp79a1 plants grew more quickly than wild-type plants but were more susceptible to insect feeding based on changes in green plant area (GPA), total leaf area, and total dry weight over time. The NILs exhibited similar patterns of growth in field trials with significant differences in leaf area and dry weight of dhurrin-free plants between the infested and non-infested treatments. Taken together, these studies reveal a significant metabolic tradeoff between CG biosynthesis and plant growth in sorghum seedlings. Disruption of dhurrin biosynthesis produces plants with higher growth rates than wild-type plants but these plants have greater susceptibility to FAW feeding.

Highlights

Plants produce many different types of metabolites that can deter insect feeding (Tattersall et al 2001; Wittstock and Gershenzon 2002) including cyanogenic glucosides (CG)
One of the key factors controlling deterrence is based on the amount of CGs within the plant tissues with higher concentrations leading to greater deterrence, as shown in a study of Japanese beetle feeding in 24 Prunus species (Patton et al 1997)
Comparisons of green plant area (GPA) with total leaf area measured by destructive sampling and fall armyworm (FAW) feeding showed an R2 of 0.86 (Fig. 3b)

Summary

Introduction

Plants produce many different types of metabolites that can deter insect feeding (Tattersall et al 2001; Wittstock and Gershenzon 2002) including cyanogenic glucosides (CG). CGs are a family of compounds found in over 2500 plant species (Jones 1998; Conn 1981; Gleadow and Woodrow 2002; Gleadow and Møller 2014), including sorghum, bitter almond (Hosël and Conn 1982), and cassava, and are thought to play key roles in deterring insect feeding (Gleadow and Woodrow 2002). Alternate food sources can influence feeding patterns as insects will generally avoid feeding on plant tissues with high concentrations of CGs if an alternative food source is available (Gleadow and Møller 2014). Krothapalli et al (2013) demonstrated that the -glucosidase that catalyzes rapid HCN release in sorghum,

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