Differential Responses of Guayule (Parthenium argentatum Gray) Genotypes to Culture Filtrate and Toxin from Macrophomina phaseolina (Tassi) Goidanich

Abstract

The potential for using cell-free culture filtrate (CFCF) and toxin (phaseolinone) from Macrophomina phaseolina for rapid and efTective screening procedures for charcoal rot resistance in guayule (Parthenium argentatum) germplasm was assessed. The CFCF and partially purified phaseolinone were incorporated into modified Murashige and Skoog solid medium at the rates of 0-100% (v/v) and 0-1000^g ml"', respectively. The medium pH was adjusted to 5.8 before solidifying with 0.8% agar. Fourweek-old seedlings of 10 guayule genotypes were planted in the medium, incubated and rated for phytotoxic symptoms and tissue damage over a 15-day period. In a greenhouse study, seedling growth, phytotoxicity and damage severity were compared in 12-week-o!d guayule seedlings root-inoculated with M. phaseolina microsderotia. There were significant differences (P = 0.05) in genotypic responses to the fungus, the filtrate and the toxin inoculations. Time until phytotoxic symptoms developed was inversely related to the concentrations of CFCF and the toxin. Phytotoxic symptoms were produced 6 days after exposure to 50% CFCF and 48 h after exposure to 1000/jg ml"' of partially purified phaseolinone. A comparison of photomicrographs of the control and toxintreated root tissues revealed no damage to the control roots and extensive damage to epidermal layers of the treated roots, which was evident 48 h after exposure to lOO^g ml"' level of phaseolinone. Significant correlations were found between tolerance to the fungus and insensitivity to the culture filtrate (r = 0.89, P = 0.05) and the toxin (r = 0.95, P = 0.001) suggesting the possibility of screening for resistance to M. phaseolina using CFCF or phaseolinone. The genotypic reactions to the CFCF were also correlated with reactions to the toxin {r = 0.90, P = 0.05). Guayule breeding lines 'UCIOT and 'P3-r exhibited the greatest tolerance to the pathogen and insensitivity to the CFCF or the toxin whereas 'Cal6', 'Cal7', 'N576', 'N9-5', M1605' and 'N6-5' were very susceptible to the pathogen and sensitive to the CFCF or the toxin. Zusammenfassung Unterscbiedliche Reaktionen von Guayole-Genotypen {Par-themum argentatum Gray) gegenuber dem Kulturflltrat and dem Toxin von Macrophomina pkaseolina (Tassi) GoidanichUntersucht wurde die mogliche Anwendung von zellfreiem Kulturfiltrat (CFCF) und dem Toxin (Phaseolinon) von Macrophomina phaseolina in einem schnellen und zuverlassigen Verfahren bei der Resistenzprtlfung in Guayule {Parthenium argentatum). Das CFCF und das teilgereinigte Phaseolinon wurden dem modifizierten Murashige und Skoog-Agarmedium in den Konzentrationen 0 bis 100% (v/v) bzw. 0 bis 1000 /ig/ml beigemischt. Der pH-Wert des Mediums wurde bei 5,8 eingestellt und anschlieBend mit 0,8% Agar versehen. Vier Wochen alte Samlinge von 10 Guayule-Genotypen wurden in diesen Medien gepflanzt, inkubiert und bonitiert auf phytotoxische Symptome und Gewebezerstorung uber einem Zeitraum von 15 Tagen. Das Samlingswachstum, die Phytotoxizitat sowie die Befallsintensitat wurden in Gewachshausversuc...

Soybean Charcoal Rot Disease Fungus Macrophomina phaseolina in Mississippi Produces the Phytotoxin (−)-Botryodiplodin but No Detectable Phaseolinone

“…2 The fungus is also an important reason for the failure of semiarid agriculture with crops such as guayule. 3 Research on charcoal rot and other plant diseases caused by M. phaseolina has been severely hampered by the unavailability of phaseolinone (1), a phytotoxin believed to play a role in the initial infection of roots, although this role remains to be established experimentally. The phytotoxin from M. phaseolina was first identified by Siddiqui et al 4 in culture filtrates of the fungus and reported by Dhar et al 5 to be 1, an eremophilane sesquiterpenoid, specifically an epoxidized analogue of phomenone.…”

“…Charcoal rot disease, one of about 500 plant diseases caused by the fungus Macrophomina phaseolina , is responsible for major economic losses to soybean producers in dry years . The fungus is also an important reason for the failure of semiarid agriculture with crops such as guayule . Research on charcoal rot and other plant diseases caused by M. phaseolina has been severely hampered by the unavailability of phaseolinone ( 1 ), a phytotoxin believed to play a role in the initial infection of roots, although this role remains to be established experimentally.…”

Effect of necrotrophic fungus and PGPR on the comparative histochemistry of Vigna radiata by using multiple microscopic techniques

“…Once entered the vascular tissues, fungus plugs the vessels by spreading through the cells (Wyllie, 1998). Enzymatic degradation and toxin production may also lead to charcoal rot (Jones & Wang, 1997; Kuti, Schading, Latigo, & Braford, 1997). M. phaseolina secretes an array of cell wall degrading enzymes which depolymerize the cell wall components such as cellulose, xylan, pectin, polygalacturonic acid and other proteins (Khan et al, 2017).…”

Phytotoxic Responses of Soybean (Glycine max L.) to Botryodiplodin, a Toxin Produced by the Charcoal Rot Disease Fungus, Macrophomina phaseolina

“…An example of the impact of charcoal rot disease on agriculture was provided by attempts to establish commercial natural rubber production with guayule (Parthenium argentatum Gray) in the arid southwest region of the US as an alternative to imported material from the rubber tree (Hevea brasiliensis) [2]. Guayule rubber production was only competitive when plants were grown close enough together that the roots interdigitated, under which conditions charcoal rot could spread from plant to plant destroying the crop [3]. Because charcoal rot is favored by hot, dry conditions [4], it is a climate-impacted plant disease that is predicted to be an increasingly important agronomic problem going forward, given that climate change is predicted to result in hotter, drier conditions in the majority of the world [5].…”