In culture (PDA medium, 39 g/l), colonies are circular-radial, flat, greyish-brown and have a growth rate of 5.3 mm/day at 25 ± 1°C in the dark (Astiz Gassó and Marinelii, 2003;2013). The mycelium is branched and septate, typical of basidiomycetes. Teliospores are reddish brown and can differ in size depending on the number of cells. A single cell spore is 20 μm, whereas spores composed of eight cells can be 50 μm in size (Marraro Acuña et al., 2013;Rago et al., 2017).
Symptoms of the disease are characteristic and easy to identify in the field. As the aerial part of the plant is asymptomatic, it is necessary to open pods at advanced stages of development to detect the pathogen (Rago et al., 2017). Disease assessment is performed when a given field is to be harvested of mature pods (R8). It is only in this phenological state that it is possible to estimate the severity of the disease in samples. Infection can be seen in immature pods, but it is difficult to estimate severity. One of the tools for monitoring the disease is based on the quantification of spores in the plot to be planted. This is done through sampling and observing soil suspensions under the microscope. Oddino et al. (2010) related the amount of inoculum present in a plot with the incidence of the disease.
Related invasive species
- Thecaphora frezii
Related Farm Practice
- Hosts
Related location
- Brazil
- Argentina
- Bolivia
Thecaphora frezii is the causal agent of peanut smut. The disease was first reported in 1962 in wild peanuts from Aquidauana, Mato Grosso do Sul, Brazil. It was first detected in commercial crops in 1995 in the central-northern area of Córdoba province, Argentina. The prevalence of peanut smut has gradually increased. In the 2011/12 growing season, the disease was found in all production fields in Córdoba province and, two years later, it was found in all peanut production areas of Argentina. The increase in the intensity of peanut smut in Argentina has been accompanied by increasing yield losses.
Infection is localized and infected plants do not exhibit aerial symptoms. Affected pods exhibit hypertrophy and have a spongy consistency, and kernels can be replaced, partially or totally, by a reddish-brown mass of spores.
Arachis is the only host reported for T. frezii (Rago et al., 2017). The disease has been reported in commercial peanut crops in Argentina, but only occurs in wild peanuts in Brazil and Bolivia (Carranza and Lindquist, 1962;Soave et al., 2014). All of the peanut cultivars that are widely planted in Argentina are susceptible (Cignetti et al., 2010a).