Identification, Laboratory, Greenhouse, and Field Handling of Aphanomyces euteiches on Pea (Pisum sativum)

Abstract

Aphanomyces euteiches is a destructive soilborne plant pathogen, causing economic losses when adequate to excess soil moisture is available. This oomycete organism survives in the soil for decades and infects and degrades roots of plants from 11 families. Symptoms of Aphanomyces root rot are similar across the major economic hosts alfalfa (Medicago sativa subsp. sativa L.), lentil (Lens culinaris Medik.), and pea (Pisum sativum L.). Initial symptoms include the appearance of grey, water-soaked root tissue. Roots develop a golden-brown color, and lateral roots begin to disintegrate as the disease worsens. In the most severe cases, the entire root system is destroyed and aboveground chlorosis and necrosis are observed. A. euteiches isolation can be successful from both infested soil and infected plant tissue. Macroscopically, colony growth is generally nondescript and white in color. A. euteiches is self-fertile (homothallic) and produces sexual oospores in culture in addition to asexual zoosporangia and zoospores (primary and secondary) on hyphae lacking regular septa (coenocytic). Numerous molecular techniques have been developed for successful A. euteiches detection. A. euteiches can be stored in frozen soil or on agar slants, but viability should be evaluated regularly. Oospores or zoospores have been utilized for inoculation under greenhouse and field conditions; although the generation of a field site using soil infestation techniques can take several seasons of productions of a susceptible crop to be utilized to effectively screen for Aphanomyces root rot.

A greenhouse-based high-throughput phenotyping platform for identification and genetic dissection of resistance to Aphanomyces root rot in field pea

“…Eight to 10 yellow corn kernels and 75mL of deionized water were placed into a 250mL Erlenmeyer flask and autoclaved for 20 minutes (Carlson 1965; Zitnick-Anderson et al 2021). Five agar plugs (approximately 2mm diameter) were transferred from a 7-to 10-old A. euteiches culture grown on cornmeal agar (CMA) (1L distilled water and 17g CMA [BBL CMA, BD Biosciences, San Jose, CA, United States) to the autoclaved flask containing corn kernels.…”

“…Aphanomyces root rot (ARR), caused by Aphanomyces euteiches Drechs., is one of the most destructive pea diseases, causing up to 100% crop failure (Gaulin et al 2007; Gossen et al 2016; Zitnick-Anderson et al 2021). In North Dakota, which is the primary target environment of the North Dakota State University (NDSU) pulse breeding program, the disease was first identified in 2014, and since then has been prevalent in pulse-growing regions across North America (Heyman 2008; Sivachandra Kumar et al, 2021; Zitnick-Anderson and Pasche 2016).…”

“…The symptoms of ARR initially appear as water-soaked and grayish discoloration. As the disease progresses, the roots exhibit honey-brown discoloration and become soft (Gossen et al 2016; Zitnick-Anderson et al 2021), lateral and root hairs start to decay, and in advanced stages the entire root mass can turn blackish and decays (Gossen et al 2016). The symptoms can also extend to the epicotyl giving the lower stem a shrunken appearance, and further disease development can lead to chlorosis, necrosis, stunting, and death of older leaves, that may progress upward along with the shoot (Heyman 2008; Gossen et al 2016).…”

“…Environmental conditions play a role in the success of a cultivar regionally, but resistance is also dependent on the pathogen population. Aphanomyces euteiches has been demonstrated to vary in aggressiveness as well as genetically; therefore, it is imperative that both host and pathogen factors are evaluated on a regional basis (Grünwald and Hoheisel et al 2006; LeMay et al 2018; Quillévéré-Hamard et al 2018; Zitnick-Anderson et al 2021). Combining just seven of the genomic regions for partial resistance into a new cultivar has resulted in decreased ARR severity (Lavaud et al 2016).…”

A greenhouse‐based high‐throughput phenotyping platform for identification and genetic dissection of resistance to Aphanomyces root rot in field pea

“…Environmental conditions play a role in the success of a cultivar regionally, but resistance is also dependent on the pathogen population. A. euteiches has been demonstrated to vary in aggressiveness as well as genetically; therefore, it is imperative that both host and pathogen factors are evaluated on a regional basis (Grünwald & Hoheisel et al, 2006;LeMay et al 2018;Quillévéré-Hamard et al, 2018;Zitnick-Anderson et al, 2021). Combining just some of the seven main genomic regions previously identified for partial resistance (Hamon et al, 2013) into a new cultivar has resulted in decreased ARR severity (Lavaud et al, 2016).…”