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Research Project: Genetic Improvement of Crop Plants for Use with Low Quality Irrigation Waters: Physiological, Biochemical and Molecular Approaches

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Title: Salt tolerance and growth of 13 avocado rootstock related best to chloride uptake

Author
item Celis, Nydia
item Suarez, Donald
item WU, LAOSHENG - University Of California
item LI, RUI - University Of California
item MAUK, PEGGY - University Of California

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2018
Publication Date: 12/1/2018
Citation: Celis, N., Suarez, D.L., Wu, L., Li, R., Mauk, P. 2018. Salt tolerance and growth of 13 avocado rootstock related best to chloride uptake. HortScience. 53(12):1737-1745. https://doi.org/10.21273/HORTSCI13198-18.
DOI: https://doi.org/10.21273/HORTSCI13198-18

Interpretive Summary: Avocado is one of the most salt sensitive crops, and one of the highest value crops per acre. In the U.S., avocados are grown primarily in California; in regions experiencing both scarcity of fresh water and salinization of available water supplies. We evaluated avocado rootstocks for salt tolerance and the relationship between leaf ion concentrations and growth and fruit yield. We examined the salt tolerance of 13 different avocado rootstocks grafted onto Hass scion with a total of 252 trees with six replications of each saline (EC=1.5 dS m-1) and non-saline (EC= 0.5 dS m-1) treatments with corresponding chloride concentrations of 0.73 mmolc L-1 and 4.94 mmolc L-1 respectively. The rootstocks that had high concentrations of chloride and sodium in the leaves were also the least salt tolerant, having 100 % mortality in the rows irrigated with saline water for 23 months. The rootstocks that had low concentrations of chloride ions in the leaves were also the rootstocks whose growth and fruit yield were least affected by salinity, exhibiting the highest yields, largest trunk diameters and highest survival percentages in the salt treatment. Overall, yield parameters correlated well with leaf chloride concentration, but not sodium, indicating that salt damage in avocado is primarily due to chloride ion toxicity. This salt tolerance information is of use to avocado growers, farm advisors and consultants regarding rootstock selection for new plantings. The correlation of salt tolerance to leaf chloride compositions is of direct interest to avocado breeders as it provides information as to the main trait for avocado salt tolerance.

Technical Abstract: Avocado (Persea americana Mill.) is one of the most salt-sensitive crops and one of the highest value crops per acre. In the United States, avocados are grown primarily in California, in regions experiencing both scarcity of freshwater and salinization of available water supplies. Thus, our objectives were to evaluate avocado rootstocks for salt tolerance and evaluate the relationship between leaf ion concentrations, trunk diameter, leaf burn, and fruit yield. Our field experiment evaluated the salt tolerance of the Hass scion grafted onto 13 different avocado rootstocks using the Brokaw clonal rootstock technique. The experiment consisted of 156 trees arranged in a randomized complete block design with six replications of each saline [electrical conductivity (EC) = 1.5 dS·m–1, Cl– = 4.94 mmol·L–1] and nonsaline (EC= 0.65 dS·m–1, Cl– = 0.73 mmol·L–1) irrigation water treatment. We collected soil samples and leaves, then analyzed them for major ions. The rootstocks R0.06, R0.07, PP14, and R0.17, which had high concentrations of Cl and Na in the leaves, were the least salt tolerant, with 100% mortality in the rows irrigated with saline water for 23 months. The rootstocks R0.05, PP40, R0.18, and Dusa, which had low concentrations of Cl ions in the fully expanded leaves, were least affected by salinity, and these rootstocks exhibited the greatest yields, largest trunk diameters, and greatest survival percentages in the saline treatment. Yield and growth parameters correlated well with leaf Cl concentration, but not Na, indicating that salt damage in avocado is primarily a result of Cl ion toxicity. Under arid inland environments, no variety performed satisfactorily when irrigated with an EC = 1.5 dS·m–1 water (Cl– = 4.94 mmol·L–1). However, the more tolerant varieties survived at soil salinity levels that would apparently be fatal to varieties reported earlier in the literature.