Prevalence and pathogenicity of spinach root pathogens of the genus Pythium in Sweden

Abstract

Several pathogenic Pythium spp, were isolated from spinach roots in a 4-year disease survey in commercial spinach fields in southern Sweden. Heterothallic and zoospore-producing isolates belonging to the filamentous, non-inflated zoosporangia (F) group of van der Plaats-Niterink were most abundant, followed by P. sylvaticum, P. ultimum var, ultimum and P. heterothallicum. The heterothallic hyphal swelling (HS) group and P. tracheiphilum were found in a few plants. Two types of pathogenicity tests were performed, to measure the effects of seedling infection and of root infection of older plants. These tests showed P. ultimum var, ultimum to be the most severe spinach pathogen inducing pre-and postemergence damping off as well as root rot of older plants. Also P. heterothallicum and P. tracheiphilum damaged both seedlings and older plants, Pythium sylvaticum, Pythium 'group HS" and Pythium 'group F' were pathogenic only to seedlings, P. ultimum var, ultimum and Pythium group F were isolated in significantly higher frequencies from spinach grown in the autumn season than in the spring. No clear relationships were found between Pythium prevalence and disease severity index of surveyed field plants, between Pythium prevalence and plant developmental stage, or between prevalence of Pythium and other pathogens isolated. This is the first report of P. heterothallicum and P. sylvaticum being pathogenic on spinach.

First report of Globisporangium heterothallicum causing root and crown rot of pepper in Turkey

“…Globisporangium heterothallicum was reported as a pathogen on a number of hosts including spinach in Sweden (Larsson, 1994), corn in China (Gan et al ., 2010), soybean in Pennsylvania, USA (Coffua et al ., 2016), alfalfa in Minnesota, USA (Berg et al ., 2017), and grapevine in South Africa (Langenhoven et al ., 2018). To our knowledge, this is the first report of G. heterothallicum causing root and crown rot of pepper in Turkey.…”

First record ofPythium tracheiphilumassociated with lettuce wilt and leaf blight in Australia

“…pekinensis) in Denmark, with losses of 40 to 50% (Møller and Hockenhull 1997). It has also been recorded as a root pathogen of spinach (Spinacea oleracea) in Sweden (Larsson 1994), sugar beet (Beta vulgaris) in Iran (Noor et al 2004) and as a cause of dampingoff of pine (Pinus halepensis) seedlings in Algeria (Paul et al 1992). Blok and van der Plaats-Niterink (1978) showed that P. tracheiphilum was highly pathogenic to cucumber (Cucumis sativus) and cauliflower (Brassica oleracea var.…”

From seed to seedling - damping-off tolerance in Spinacia oleracea L

“…Previous studies have characterised P. ultimum as the most prevalent damping-off pathogen in spinach fields in Sweden (Europe) (Larsson, 1994) and California (USA) (Koike et al, 2011). P. ultimum Trow, 1901, is one of the over 230 species of the genus Pythium Pringsheim, 1858, which is the largest and most comprehensively studied genus in the family of Pythiaceae, order Peronosporales, class Peronosporomycetes, phylum Oomycota, and kingdom Stramenopila (= Chromista) (Plaats-Niterink, 1981;Beakes et al, 2014).…”

“…(Kamoun et al, 1999). Pythium species that can cause damping off of spinach include, for example, Pythium aphanidermatum, P. paroecandrum (Naiki et al, 1986), P. ultimum, P. heterothallicum, P. sylvaticum (Larsson, 1994), and P. spinosum (Hirayama & Tojo, 1999). Studies have characterised P. ultimum as the most prevalent damping-off pathogen in spinach fields in Sweden (Europe) (Larsson, 1994) and in California (USA) (Koike et al, 2011).…”

“…Multiple studies on damping-off diseases have characterised Pythium spp. as the most prevalent damping-off pathogens in spinach fields in Sweden (Europe) (Larsson, 1994), in California (USA) (Koike et al, 2011), and in Georgia (USA) (Sumner et al, 1976). Generally, damping off occurs more frequently in wet, compacted soils, but the severity of damping off is dependent on a multitude of factors, such as the plant species and genotype, pathogen species, abundance, and pathogenicity, and management practices (Lamichhane et al, 2017).…”