Seeds of weeds as an alternative host of phytopathogens

Abstract

Weeds compete with agricultural crops for water, light, nutrients and space, besides having an extensive seed bank. However, another aspect to be considered relates to few studies pointing out weeds as hosts of phytopathogenic fungi. Many fungi, the main cause of diseases in plants, are known to use seeds as an efficient means of survival and dispersal. The objective of this work was to evaluate the health of weed seeds and the pathogenicity of fungi associated to plants of agricultural importance. The seeds were collected manually in Cerrado areas located in the municipality of Gurupi, Tocatins, Brazil. The blotter test method was used to evaluate seed health. The incidence of fungi was evaluated through an individual analysis of seeds using a stereoscopic and an optical microscope. The pathogenicity of fungi from weed seeds was evaluated by inoculation in plants of agronomic interest and, when pathogenic, we inoculated them in the host plant of the fungus. Weed seeds have been identified in fungi of the genus Alternaria, Aspergillus, Bipolaris, Cladosporium, Curvularia, Fusarium, Nigrospora, Papularia, Rhizopus and Pythium. The seeds of Acanthospermum australe, Bidens pilosa, Cenchrus echinatus, Digitaria horizontalis, Echinochloa crus-pavonis, Eleusine indica, Ipomoea sp., Pennisetum setosum, Sida rhombifolia, Spermacoce latifolia, Tridax procumbens and Vernonia polyanthes carry and disseminate fungi that, once inoculated, cause infection in plants of agricultural importance, such as Oryza sativa, Phaseolus vulgaris, Vigna unguiculata, Zea mays and Glycine max.

Pythium and Phytopythium species associated with weeds collected in vegetable production fields in Brazil

“…This weed can also act as a host of pests and diseases, causing significant losses of yield in agricultural crops (Kissmann and Groth 1999; Oliveira et al . 2018). In S. oleraceus , diseases that are common in lettuce, such as downy mildew ( Bremia lactucae ), are commonly observed, as both plants belong to the Asteraceae family (Vardhana 2017; Mendes and Urben 2020).…”

“…Bidens pilosa is found in practically all regions of Brazil during all seasons of the year, and is a very aggressive invasive weed competing with crops for many resources. This weed can also act as a host of pests and diseases, causing significant losses of yield in agricultural crops (Kissmann and Groth 1999;Oliveira et al 2018). In S. oleraceus, diseases that are common in lettuce, such as downy mildew (Bremia lactucae), are commonly observed, as both plants belong to the Asteraceae family (Vardhana 2017;Mendes and Urben 2020).…”

Evaluation of smart spray technology for postemergence herbicide application in row middles of plasticulture production

“…(Lopez et al 2021); and phytopathogenic fungi such as Curvularia sp., Fusarium sp., and Pythium sp. (Oliveira et al 2018).…”