Macrophomina Crown and Root Rot of Pistachio in California

Abstract

In this study, declining pistachio rootstocks were detected in newly planted commercial pistachio orchards in Kern County, California. Symptoms were characterized by wilted foliage combined with crown rot in the rootstock. From diseased trees, 42 isolates were obtained, and all had similar cultural and morphological characteristics of Macrophomina phaseolina. Analyses of nucleotide sequences of three gene fragments, the internal transcribed spacer region (ITS1–5.8S–ITS2), partial sequences of β-tubulin, and translation elongation factor 1-α (TEF1) confirmed this identification, and 20 representative isolates are presented in the phylogenetic study. Testing of Koch’s postulates showed that M. phaseolina, when inoculated to stems and roots of the pistachio rootstocks using mycelial plugs or a microsclerotial suspension, is indeed pathogenic to this host. The widely used clonal University of California Berkeley I (UCBI) rootstock appeared highly susceptible to M. phaseolina, suggesting that this pathogen is an emerging threat to the production of pistachio in California. This study confirmed the association of M. phaseolina with the decline of pistachio trees and represents the first description of this fungus as a crown rot-causing agent of pistachio in California.

Diversity of Botryosphaeriaceae species associated with canker and dieback of avocado (Persea americana) in Italy

“…This pathogen causes charcoal rot of soybean (Sarr et al, 2014), chickpea (Dell'Olmo et al, 2022, sunflower (Bokor, 2007), sorghum (Sharma et al, 2014), and strawberry (Koike, 2008). It has also been reported to cause diseases on woody hosts, such as grapevine (González and Tello, 2011;Nouri et al, 2018), olive (Sergeeva et al, 2005), pistachio (Nouri et al, 2020), and almond (Inderbitzin et al, 2010). Macrophomina phaseolina was thought to be one of the pathogens causing avocado root rot in Australia (Poudel et al, 2021), but it has not been recorded as causing canker on this host.…”

Molecular interactions between the soilborne pathogenic fungus Macrophomina phaseolina and its host plants

“…M. phaseolina also poses a great threat to specialty crops, such as strawberry, pistachio, and sunflower ( Mertely et al., 2005 ; Bokor, 2007 ; de los Santos et al., 2019 ; Nouri et al., 2020 ). Research on specialty crops is often underfunded and disproportionately lacking in comparison to the steady rise in value of production, despite the inherently high risk involved in marketing fresh produce ( Alston and Pardey, 2008 ; Neill and Morgan, 2021 ).…”

Advances in Rootstock Breeding of Nut Trees: Objectives and Strategies

“…However, as this problem proved to be non-transmissible in the field, and nurseries can now identify it in young rootstocks, it is no longer a problem. Nouri et al [238] reported a new pathogen, Macrophomina phaseolina in Kern County of California which is characterized by wilted foliage combined with crown rot of the rootstock. UCB1 is highly susceptible to M. phaseolina and this pathogen is now an emerging threat to pistachio production in California.…”