Expression of pathogenesis-related (PR) genes in avocados fumigated with thyme oil vapours and control of anthracnose

Abstract

Highlights• Thyme oil fumigation effectively controlled the anthracnose in avocados.• Defence enzymes (chitinase and β-1,3-glucanase) were induced by thyme oil fumigation.• Thyme oil fumigation initiated the expression and activities of defense enzymes. AbstractThyme oil (TO) fumigation (96 μL L -1 ) to cv. Hass and Ryan avocados significantly reduced anthracnose incidence compared to prochloraz and to untreated control. Also enhanced activities of β-1,3-glucanase, chitinase were noted in both cultivars. TO fumigation induced the expression of both β-1,3-glucanase and chitinase genes in naturally infected fruit of both cultivars, during storage at 7 or 7.5 °C for up to 21 d and during subsequent simulated market shelf conditions at 20 °C for 5 d. However, the impact of TO fumigation on the β-1,3-glucanase gene expression was higher in both cultivars. Higher gene regulation and β-1,3-glucanase, chitinase activities were observed in cv. Ryan compared to Hass. Although TO 2 fumigation significantly reduced anthracnose incidence in both naturally infected cultivars, the inhibitory effect was slightly higher in cv. Ryan than Hass. Thus postharvest TO fumigation had positive effects on enhancing anthracnose disease resistance during storage and also gave a residual effect during the simulated shelf life.

Control of anthracnose disease via increased activity of defence related enzymes in ‘Hass’ avocado fruit treated with methyl jasmonate and methyl salicylate

“…After placing the fruit in a 10 l air-tight container, the appropriate volume of MeJA or MeSA to reach the desired concentration of 10 and 100 µmol l -1 , respectively was deposited on the Petri dish at the bottom of the container (Gimenez et al, 2016), using the system set up previously designed for the thyme oil fumigation (Bill, Sivakumar, Beukes, & Korsten, 2016). The container was immediately hermetically-sealed and solutions were left to evaporate over the 24 h period.…”

“…Control and prochloraz ® treated fruit were also kept in similar sealed containers. Thereafter half of the fruit were wounded and inoculated at the equatorial region with 20 µl of C. gloeosporioides spore suspension (10 5 spores ml -1 ) as previously described (Bill et al, 2016). Both naturally and artificially infected 'Hass' avocado fruit were subsequently kept at 2.0±0.2 °C for 14 d followed by 6-7 d shelflife at 20.0±0.5 °C, RH 70 %.…”

“…Colletotrichum gloeosporioides was obtained from the Fruit and Vegetables Technology Laboratories, Tshwane University of Technology, South Africa. The C. gloeosporioides isolate was cultured and maintained on potato dextrose agar (PDA) (Merck, Johannesburg, South Africa) and incubated at 25 °C for 12-13 d. Spore suspension was prepared following a method of Bill et al (2016). The mycelia fragments were removed from the suspension by filtering through three layers of muslin cloth.…”

Impactos al fruto de aguacate ‘hass’ en la línea de empacado y su efecto en la calidad postcosecha

“…Algo similar se realizó para evaluar la calidad interna del fruto, aunque en este caso se abrió cada fruto por mitad. Otros desórdenes internos, como decoloración de la pulpa, oscurecimiento vascular, y pudrición basal no fueron considerados, ya que no son ocasionados por impactos en los frutos (Bill et al, 2016).…”

“…Something similar was done to evaluate the internal quality of the fruit, although in this case each fruit was opened in half. Other internal disorders, such as pulp discoloration, vascular darkening, and basal rot were not considered, as they are not caused by impacts on fruits (Bill et al, 2016).…”