Changes in Tea Plant Secondary Metabolite Profiles as a Function of Leafhopper Density and Damage
Front. Plant Sci., 29 May 2020
Eric R. Scott, Li, Wei, Kfoury, Morimoto, Guo, Agyei, Robbat, Ahmed, Cash, Griffin, Stepp, Han, Orians et all.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272924/
The tea green leafhopper (Empoasca onukii) can be a widespread pest on tea, but some tea farmers take advantage of leafhopper-induced metabolites in order to produce high-quality “bug-bitten” teas such as Eastern Beauty oolong. To understand the effects of increasing leafhopper density on tea metabolites important for quality, we conducted a manipulative experiment exposing tea plants to feeding by a range of E. onukii densities. After E. onukii feeding, we measured volatile and non-volatile metabolites, and quantified percent damaged leaf area from scanned leaf images. E. onukii density had a highly significant effect on volatile production, while the effect of leaf damage was only marginally significant. The volatiles most responsive to leafhopper density were mainly terpenes that increased in concentration monotonically with density, while the volatiles most responsive to leaf damage were primarily fatty acid derivatives and volatile phenylpropanoids/benzenoids.
My summary:
Study method:
tea: qing xin da mao cultivar (commonly used for OB)
leaf hopper: Empoasca onukii
Matsuda leaf hopper density in a field at Shanfu tea company: 0.12-0.36 hoppers/leaf (for real world comparison purposes)
treatment in study: 0, 0.5, 1, 1.5, 2 hoppers/leaf (these are the target treatments for the experiment. They estimate actual ratio at sampling.)
volatile sampling of undried leaf:
- 2 hours from representative leaf in each pot by direct contact sorptive extraction. Volatiles analyzed by gas chromatography - mass spectrometry
leaves were dried by microwave and analyzed for:
- leaf damage through pixel classification by machine learning
- non-volatile metabolites in extraction (80:15:5 acetonitrile:water: 1 M HCl extraction reagent) by LC-MS
- total phenolic content by Folin Ciocalteau assay
take aways:
Strongest correlations between hopper/leaf and the following volatiles:
cis-3-hexenyl butyrate: wine,
green(E,E)-α-farnesene: woody, sweet, green , floral
sulcatone: citrus, green, musty, cheesy
(Z)-3-hexenyl hexenoate: green, fruity, fatty, tropical
unknown 3: unknown
(E)-β-ocimene: citrus green terepene
trans-dehydroxylinalool oxide:herbal, green, terpene
cis-linalool oxide (pyranoid):citrus, green
cis linalool oxide (furanoid): earth, floral, sweet, woody
I have attached the figure of the plots so you can decide if these relations are meaningful. Note several of these are also found in honey. Also note that some volatiles appear to plateau at about 0.3 hopper/ leaf. Some others need at least 0.6 hopper/leaf.
no significant correlation between leaf damage and volatiles
no significant correlation between hopper/leaf and non-volatiles
negative correlation between leaf damage and non-volatiles