First Report of <i>Phytophthora</i> Taxon Walnut on <i>Pistacia vera</i> in California

Fichtner, E.; Kallsen, Craig E.; Dhaouadi, Sabrine; Blomquist, C. L.

doi:10.1094/pdis-11-16-1597-pdn

Cited by 3 publications

(1 citation statement)

References 3 publications

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“…At the end of 60 d, leaf B had plateaued at only about 300 ppm. However, P. vera, as a rootstock or growing on its own roots, is susceptible to Phytophthora species under fully irrigated conditions (Banihashemi, 1995;Fichtner et al, 2017;Kallsen and Parfitt, unpublished data), which makes them unsuitable as rootstocks under California conditions. The apparent B tolerance of P. vera suggests its use as a parent in crosses with more vigorous and disease-resistance species to generate rootstocks for high-B soils.…”

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Leaflet Boron Concentration Reduced with Hybrid Pistacia vera Rootstocks

Kallsen¹,

Parfitt²

2022

horts

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Excessive boron (B) in soil and water is a problem for pistachio (Pistacia vera L.) production in the San Joaquin Valley (SJV) of California. Although amenable, leaching of B requires more water than chlorine (Cl) or sodium (Na) and is increasingly difficult as B in irrigation water increases. The lack of subsurface drainage to the ocean increases soil salinity in many growing areas, especially on the west side of the SJV where B is often excessive natively in the soil and water. Pistachio rootstocks that can tolerate or exclude B may be a partial solution. For the past decade in California, the dominant rootstock has been seedlings and clonal selections of University of California Berkeley 1 (UCB-1), which is a hybrid of P. atlantica × P. integerrima. This reliance on a genetically similar pool of rootstocks has constrained Pistacia’s genetic potential for adapting to high-salt environments. This study compared scion and rootstock leaflet B concentration of novel hybrid experimental rootstocks with variable percentages of P. vera and P. integerrima heritage with UCB-1. Rootstocks with P. vera heritage limited B in both rootstock and scion leaflets compared with UCB-1. In six trials conducted over several years, leaflet B in ungrafted hybrid rootstocks having 62.5% to 75% P. vera and 25% to 37.5% P. integerrima heritage had 27.6% to 43.1% lower B leaflet concentration than did UCB-1. Depending on the experiment and year, grafted rootstocks having 37.5% P. vera and 62.5% P. integerrima heritage had 46.8% to 70.8% lower B scion leaflet concentration than did UCB-1. Genetic variation in B uptake in Pistacia species and interspecific hybrids, and among individual seedlings within populations, allows the breeding of pistachio rootstocks more tolerant of excess B.

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confidence: 99%

Leaflet Boron Concentration Reduced with Hybrid Pistacia vera Rootstocks

Kallsen¹,

Parfitt²

2022

horts

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Phytophthora (foot rot)

2022

CABI Compendium

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Identification and Characterization of Phytophthora Species Associated with Crown and Root Rot of Pistachio Trees in California

Trouillas

Nouri²,

Bourret

2022

Plant Disease

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Pistachio is one of the most widely cultivated nut crops in California with approximately 115,000 hectares of bearing pistachio trees. In recent years, several orchards were identified with declining trees leading to substantial tree losses. Symptoms included trees with poor vigor, yellowing and wilting of leaves, crown rot and profuse gumming on the lower portion of trunks. Thirty-seven Phytophthora-like isolates were obtained from crown rot tissues in the rootstock of grafted pistachio trees and characterized by means of multi-locus phylogeny comprising ITS rDNA, beta-tubulin and mt cox1 sequence data. The analysis provided strong support for the delineation and identification of three Phytophthora species associated with declining pistachio trees, including Phytophthora niederhauserii, P. mediterranea and P. taxon walnut. Pathogenicity studies in potted UCBI rootstocks (clonal and seeded) confirmed that all three Phytophthora species can cause crown and root rot of pistachio, thus fulfilling Koch’s postulates. The widespread occurrence of Phytophthora crown rot in recently planted pistachio orchards and the high susceptibility of UCBI rootstocks suggest this disease constitute an emerging new threat to the pistachio industry of California. To the best of our knowledge, this study is the first to report P. niederhauserii, P. mediterranea and P. taxon walnut as causal agents of crown and root rots of pistachio.

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First Report of Phytophthora Taxon Walnut on Pistacia vera in California

Cited by 3 publications

References 3 publications

Leaflet Boron Concentration Reduced with Hybrid Pistacia vera Rootstocks

Leaflet Boron Concentration Reduced with Hybrid Pistacia vera Rootstocks

Phytophthora (foot rot)

Identification and Characterization of Phytophthora Species Associated with Crown and Root Rot of Pistachio Trees in California

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