Different population densities and continuous feeding byOligonychus yothersi(McGregor) (Acari: Tetranychidae) affect the emissions of herbivore-induced plant volatiles on avocado (Persea americanaMill. cv. Hass) shoots under semi-field conditions

Abstract

Plants attacked by insects and mites release blends of herbivore-induced plant volatiles (HIPVs), which act as chemical cues that attract predators and/or repel herbivores alongside alerting neighbouring plants. The chemical profiles of avocado (Persea americana Mill. Cultivar Hass) shoots infested with the foliar mite Oligonychus yothersi (Acari: Tetranychidae) were analysed using a gas chromatograph coupled to a mass spectrometer (GC-MS); the different collections of volatiles were performed under semi-field conditions in summer. Four infestation treatments were applied to the avocado shoots (uninfested plant or control; low, medium and high mite-infestation levels). The chemical profiles collected in situ changed qualitatively and quantitatively after infestation, increasing the emissions of (Z)-β-ocimene, (E)-β-ocimene, β-linalool, α-farnesene, farnesyl cyanide and methyl salicylate (MeSA) as opposed to those of the uninfested shoots. The amount of HIPVs emitted by the avocado shoots with the highest O. yothersi population density (250 ± 10 mites per leaf) were greater than those of the shoots infested with the lower population density (60 ± 10 mites per leaf); to the emissions of (E)-β-ocimene, sesquiterpenes and MeSA at higher amounts even after seventeen days of continuous infestation. Likewise, the emissions of HIPVs increased with each infestation level; also fluctuating between collecting dates, which indicates that environmental conditions maximized or constrained those emissions. In addition, the damaged foliar area increased with higher O. yothersi population densities after seventeen days of infestation. These results indicate that higher mite-population densities and continuous O. yothersi-feeding increases the amounts of HIPVs emitted by O. yothersiinfested shoots in summer. ARTICLE HISTORY

Rootstock affects the blend of biogenic volatile organic compounds emitted by ‘Hass’ avocado

“…The graft 'Hass'/'Mexicola' emitted other monoterpenes as β-pinene, cumene, 3-carene, R-limonene and (Z)-β-ocimene, and 'Hass'/'Zutano' emitted cumene (Table 1). Rioja et al (2016) collected BVOC from intact avocado 'Hass' grafted on 'Mexicola' registering the same compounds although in different concentrations. Bravo-Monzón and Espinosa-García (2008) found that 'Hass' avocado grafted on 'Criollo' rootstock released high abundance of α-pinene, β-phellandrene, β-pinene, β-myrcene, α-cubebene, α-copaene, and β-caryophyllene.…”

“…Herbivore-induced plant volatiles (HIPVs) are emitted after herbivory (Arimura et al, 2011;Gols, 2014;Heil, 2014); thus, specific odor cues are exploited by predators and parasitoids. In addition, HIPVs are modified by arthropod species, herbivores density, genotypes and plant cultivars, plant ontogeny, and abiotic factors (Hare, 2010;Hare and Sun, 2011;Proffit et al, 2011;Becker et al, 2015;Clavijo, 2016;Rioja et al, 2016).…”

“…Avocado 'Hass' emits mainly GLV, alkane and monoterpene compounds (Bravo-Monzón and Espinosa-García, 2008;Rioja et al, 2016;. Rincón-Hernández et al (2011) described differences in the chemical profile of volatiles compounds on Guatemalan, Mexican and West Indian race.…”

Herbivore-induced plant volatiles emitted from avocado shoots infested by Oligonychus yothersi (Acari: Tetranychidae) increases the attraction of micro-coleopterans

“…Eight compounds were exclusively detected in mite infested plants (Z)-3-hexen-1-ol (0.35 μg mL -1 ), 3-hexen-1-ol-benzoate (3.45 μg mL -1 ), β-myrcene (0.65 μg mL -1 ), (Z)-β-ocimene (8.11 μg mL -1 ), β-linalool (22.6 μg mL -1 ), α-farnesene (37.8 μg mL -1 ), farnesyl cyanide (18.9 μg mL -1 ) and methyl salicylate (94.1 μg mL -1 ) (Figure 1). The HIPVs identified were induced in response to O. yothersi-feeding in avocado plants (Rioja et al, 2016); those chemical compounds belong from different pathways such as GLVs, monoterpenes, sesquiterpenes and aromatic compounds, mainly. The highest emission rates were exhibited by (E)-β-ocimene, β-linalool, methyl salicylate, and α-farnesene.…”

Avocado ‘Hass’ leaf age affects life table parameters of Oligonychus yothersi (McGregor) (Acari: Tetranychidae) under laboratory conditions

“…orchards in the Valparaíso Region, Chile (Rioja et al, 2015). Oligonychus yothersi feeds on the upper leaf surface, affects leaf physiological parameters, and causes reddish color and discoloration by high oxidative stress, which is a response to O. yothersi feeding on the leaf (Hoy, 2011;Rioja et al, 2016). High O. yothersi infestations are also reported between mid-summer and late autumn, whereas the O. yothersi population is not observed during rainy seasons with low temperatures and short days (winter and early spring), indicating that those abiotic factors could affect the population outbreaks at the Quillota location (Ripa and Larral, 2008).…”