Phenotypic Variations in the Foliar Chemical Profile of Persea americana Mill. cv. Hass

Abstract

The Hass avocado tree Persea americana cv. Hass was derived from a single hybrid tree of P. americana var. drymifolia and P. americana var. guatemalensis, and it is propagated clonally by grafting. This cultivar is the most widely planted in the world but its profile of secondary metabolites has been studied rarely despite of its importance in plant protection. We illustrate the variability of the volatilome of mature leaves by describing the average chemical composition and the phenotypic variability found in 70 trees. Contrary to the uniformity expected in the Hass cultivar, high variability coefficients were found for most of the 36 detected foliar volatile compounds; furthermore we found six chemotypes grouping the foliar phenotypes of the sampled trees using hierarchical cluster analysis. About 48% of trees were grouped in one chemotype; five chemotypes grouped the remaining trees. The compounds that determined these chemotypes were: estragole, α-farnesene, β-caryophyllene, germacrene D, α-cubebene and eugenol. This striking variation in a cultivar propagated clonally is discussed in terms of somatic mutation.

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“…different compounds were detected, in the tree of the variety "Hass" were 25 and in the tree of the variety "Mendez" 29 compounds (Table 1) In "Hass" avocado trees, a smaller number of SM was identified (25), compared to a previous study, in which 34 compounds were detected in the volatile fraction of the hexane extract of foliar tissue, of which 32 were identified and two were not identified. (García-Rodríguez et al, 2016). On the other hand, so far there are no reports in the literature related to secondary metabolites identified in leaf tissue of avocado trees "Mendez".…”

“…squalene (13.9 %) and nonacosan (11.9 %) had higher concentrations, while, they were not identified in the present work. The difference in abundance may be due to the chemotype of the materials studied in each study (García-Rodríguez et al, 2016).…”

“…The ranges of abundance of the compounds estragole, karyophylene, (+) -4-carene and γ-terpinen were: 0.39 to 97.00 %, 0.56 to 71.50 %, 0.05 to 27.81 % and 0.60 to 28.63 %, respectively. In the «Hass» and «Mendez» varieties, only one individual from each variety was studied, so that it was not possible to determine the ranges of the concentrations, however, low variability was observed in these commercial varieties, probably because they are propagated in a clonal manner (García-Rodríguez et al, 2016). On the other hand, in the "Hass" variety four secondary metabolites were identified, 1,3,4,5,6,7-hexahydro-2,5,5-trimethyl 2H-2,4a-ethanonaphthalene (0.84 %), α-cubebeno (0.33 %), 2,4,6-octatrienoic acid (0.24 %) and α-felandrene (0.21 %), which were not detected in the drymifolia and "Mendez" variety (Table 1).…”

“…The karyophylene compound has antibacterial and antifungal activity (Selestino-Neta et al, 2017). (García-Rodríguez et al, 2016). Por otra parte, en la variedad "Hass" se identificaron cuatro metabolitos secundarios, 1,3,4,5,6,7-hexahidro-2,5,5-trimetil 2H-2,4aetanonaftaleno (0.84 %), α-cubebeno (0.33 %), 2,4,6-ácido octatrienoico (0.24 %) y α-felandreno (0.21 %), los cuales, no se detectaron en las variedades drymifolia y "Méndez" (Tabla 1).…”

“…No hay reportes de estos metabolitos relacionados con tolerancia a muérdago, no obstante, en el trabajo en árboles de aguacate "Hass", reportado por García-Rodríguez et al (2016), identificaron el SM α-cubebeno (4.83 %) en mayor abundancia relativa que en el presente trabajo (0.33 %), el cual presenta actividad antioxidante, antibacterial (Nivas & Gaikwad, 2014) y atrae escarabajos portadores de hongos patógenos para la planta (Kendra et al, 2016).…”