Variability of overhead volatile organic compounds in clonal tea (Camellia sinensis) and their influence on red crevice mite (Brevipalpus phoenicis Geijskes) infestations

Abstract

Abstract: Tea production in Kenya is under threat due to red crevice mites (Brevipalpus phoenicis) infestations during
droughts. Cultural pests control practices, e.g. use of resistant/tolerant cultivars are used in their control since pesticide
use is prohibited. Plants release volatile organic compounds (OVOCs) that may influence susceptibility/resistance to
pest infestations. OVOCs profiles released by 11 tea cultivars were evaluated to assess relationship between OVOCs
and cultivar tolerance/susceptibility to B. phoenicis. Five clones were susceptible, with high B. phoenicis infestations
while four clones were resistant, exhibiting low infestation levels. The infestations were linearly correlated to (E)-2-hexenal,
(Z)-3-hexenal (p≤0.001), (Z)-3-hexenol, (Z)-3-hexenyl acetate, linalool, germacrene D, sum of green leaf volatiles
(GLVs) (p≤0.01), 1-pentene-3-ol, hexanal, indole and (E)-ß-ocimene (p≤0.05) levels. Most of aromatic compounds,
some terpenoids compounds and sum of aromatic compounds were inversely (p≥0.05) correlated with B. phoenicis infestations.
Susceptible varieties to B. phoenicis emitted high amounts of GLVs, especially (E)-2-hexenal, (Z)-3-hexenal,
(Z)-3-hexen-1-ol and (Z)-3-hexenyl acetate. Results demonstrate that OVOCs profile may provide selection criteria for
cultivars resistant to B. phoenicis infestations. Resistant cultivars are recommended for commercial exploitation in red
crevice mites prone areas while breeding/selection programmes should incorporate OVOCs profiles to develop tea cultivars
that resist red crevice mites attack.