Abstract
Salt stress is a major limiting factor in avocado (Persea americana) cultivation, exacerbated by global trends towards scarcity of high-quality water for irrigation. Israeli avocado orchards have been irrigated with relatively high-salinity recycled municipal wastewater for over three decades, over which time rootstocks were selected for salt-tolerance. This study’s objective was to evaluate the physiological salt response of avocado as a function of the rootstock. We irrigated fruit-bearing ‘Hass’ trees grafted on 20 different local and introduced rootstocks with water high in salts (electrical conductivity of 1.4–1.5 dS/m). The selected rootstocks represent a wide range of genetic backgrounds, propagation methods, and horticultural characteristics. We investigated tree physiology and development during two years of salt exposure by measuring Cl and Na leaf concentrations, leaf osmolality, visible damages, trunk circumference, LAI, CO2 assimilation, stomatal conductance, spectral reflectance, stem water potential, trichomes density, and yield. We found a significant effect of the rootstocks on stress indicators, vegetative and reproductive development, leaf morphogenesis and photosynthesis rates. The most salt-sensitive rootstocks were VC 840, Dusa, and VC 802, while the least sensitive were VC 159, VC 140, and VC 152. We conclude that the rootstock strongly influences avocado tree response to salinity exposure in terms of physiology, anatomy, and development.
Highlights
Commercial modern fruit orchards are typically composed of trees with scions grafted on to rootstocks of different genetic origins
The highest Cl levels in 2020 were found in Dusa and and Na were compared with toxicCl thresholds for avocado
The rootstocks that exhibited the highest leaf Cl concentration (VC 840 and Dusa, Figure 1) were both of a Mexican genetic background, which is characterized by this trait [17,45,46]
Summary
Commercial modern fruit orchards are typically composed of trees with scions grafted on to rootstocks of different genetic origins. Grafting is a major element of propagation processes and rootstock selection is a key component in successful and healthy orchard establishment [1]. Rootstock selection can be based on adaptability to soil characteristics, pest and/or disease pressure, and desired root–scion propagation and growth interactions. The expansion of avocado cultivation areas might be challenging due to the crop’s susceptibility to stress brought upon by weather, irrigation water quality, and soil conditions including temperature, acidity, oxygen availability, and salinity [3,4,5,6]. The sensitivity of avocado to such conditions highlights that trees must be conditioned and adjusted to their specific local environment. Rootstocks must be matched to cultivation conditions and rootstock–scion relationships and subsequent crop performance should be evaluated. Rootstocks have long been used to help sensitive species cope with biotic and abiotic stresses
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