The physiological response of ‘Hass’ avocado to salinity as influenced by rootstock

Authors: ACOSTA-RANGEL, ALEYDA - University Of California; LI, RUI - University Of California; Marquez Celis, Nydia; Suarez, Donald; SANTIAGO, LOUIS - University Of California; ARPAIA, MARY - University Of California; MAUK, PEGGY - University Of California

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2019
Publication Date: 7/18/2019
Citation: Acosta-Rangel, A.M., Li, R., Celis, N., Suarez, D.L., Santiago, L.S., Arpaia, M.L., Mauk, P.A. 2019. The physiological response of ‘Hass’ avocado to salinity as influenced by rootstock. Scientia Horticulturae. 256. https://doi.org/10.1016/j.scienta.2019.108629.
DOI: https://doi.org/10.1016/j.scienta.2019.108629

Interpretive Summary: With increasing water demands and drought,, agricultural production is challenged with reduced water availability and water with increased salinity. Salinity is a critical issue for California growers since avocados are known to be extremely salt sensitive. We investigated ‘Hass’ scions grafted onto three different avocado rootstocks under control (electrical conductivity of 0.50 dS/m) and salinity (1.5 dS/m) conditions. Results indicated that salinity affected physiological performance of avocado trees including the efficiency of photosystem II, reductions in photosynthesis rate and water-use efficiency but leaf water potential was not affected by salinity treatment confirming that poor performance of treated trees was attributable to chloride accumulation and not physiological drought. These results are of interest to avocado growers, plant breeders seeking to develop more tolerant rootstock, as well as extension specialists and irrigation district managers.

Technical Abstract: With increasing demands on both potable and agricultural water supplies, drought, and extreme temperatures worldwide, agricultural production is challenged with reduced water availability and lower water quality. Salinity, which is associated with low water quality is a critical issue for California avocado growers and, coupled with avocado root rot, threatens the long-term sustainability of the industry since avocados (Persea americana Mill.) are known to be extremely salt sensitive. Salt tolerance of the ‘Hass’ variety, the most commonly grown scion in California, is influenced by rootstock. We investigated ‘Hass’ scions grafted onto three different avocado rootstocks under control (irrigation using water with EC=0.65 dS/m) and salinity (irrigation using water with EC=1.5 dS/m) conditions. Results indicated that, compared to control conditions, the irrigation of avocado trees using water with EC=1.5 dS/m increased canopy damage by 44%, reduced survival by half of the trees tested, and caused yield losses of more than 63%. Avocado leaves visibly damaged by the salinity treatment (named as partially burned or PB leaves) experienced photoinhibition, and reduction of photosynthetic rate and water-use efficiency, suggesting that the poor performance in carbon assimilation contributed to reductions in yield and increases in mortality. The salinity treatment did not cause water stress and the poor performance of treated trees was attributable to chloride accumulation previously reported. Leaf carbon isotopic composition was affected in trees under salinity treatment by increasing the values of d13C however, this affect was nor correlated with water-use efficiency. Overall, ‘R0.05’, ‘PP40’ and ‘Dusa’ performed similarly and, considering the conditions of the experiment and the intrinsic susceptibility of avocado trees to salinity, were superior to all other rootstocks tested. Future screenings for salinity tolerant rootstocks are required to improve yield when poor quality soil or water is used. Overall, our results showed a coordination between the physiological performance, health and productivity of the ‘Hass’ scion and how these parameters were negatively affected by salinity.