Development of three fusarium crown rot causal agents and systemic translocation of deoxynivalenol following stem base infection of soft wheat

Abstract

Fusarium pseudograminearum, F. culmorum and F. graminearum are the most important fusarium crown rot (FCR) causal agents. They have the common ability to biosynthesize deoxynivalenol (DON). To elucidate the behaviour of each of the three species, a comparative study was carried out to investigate symptom progression, fungal systemic growth and translocation of DON following stem base inoculation of soft wheat. FCR symptoms were mainly localized in the inoculated area, which extended up to the second node for all inoculated species. Only the most aggressive strains caused symptoms up to the third node. Real‐time quantitative PCR showed that fungal colonization reached the third node for all the tested species, but a low percentage of plants showed colonization above the third node following inoculation with the most aggressive strains. Fungal growth was detected in symptomless tissues but none of the three species was able to colonize as far as the head tissues. However, even if the pathogens were not detected in the heads, DON was detected in head tissues of the plants inoculated with the most aggressive strains. These results demonstrate that F. pseudograminearum, F. culmorum and F. graminearum, under the same experimental conditions, follow a similar pattern of symptom progression, fungal colonization and DON translocation after stem base infection. Differences in the extent of symptoms, fungal colonization and mycotoxin distribution were mainly attributable to strain aggressiveness. These findings provide comparative information on the events following infection of the stem base of wheat by three of the most important FCR casual agents.

Comparative studies about fungal colonization and deoxynivalenol translocation in barley plants inoculated at the base with Fusarium graminearum, Fusarium culmorum and Fusarium pseudograminearum

“…This behavior was also confirmed in a recent study by Beccari et al (2018) where they used the same Fc820 strain on soft wheat. This reveals the opportunity that in barley, in contrast to what occurs in soft wheat, F. culmorum could systemically colonize the head tissues after stem base inoculation.…”

“…These data are related with the quantification of F. culmorum strain Fc820 biomass and also with the work of Covarelli et al (2012) that showed a decreasing concentration of DON from the stem-base to the head of soft wheat. DON translocation from the base to the head was also detected in soft wheat plants inoculated at the stem-base with F. graminearum and F. pseudograminearum (Mudge et al 2006) and it was observed how this characteristic is depending on strain aggressiveness, such as symptoms extension and fungal colonization (Beccari et al 2018). In addition, Mudge et al (2006) demonstrated how strains F. graminearum mutant for tri5 gene (responsible for DON biosynthesis) were unable to colonize the adjacent area of the flag leaf in soft wheat.…”

“…Conversely, for FCR, the relationship between symptom severity, fungal biomass and mycotoxin accumulation is still poorly understood, because Fusarium causal agents do not directly colonize the head. Recently, several studies (Mudge et al 2006, Covarelli et al 2012, Winter et al 2013, Moretti et al 2014, Beccari et al 2018) investigated the colonization process of different Fusarium species and their possible systemic movement along soft and durum wheat plants after stem base inoculation. In particular, Covarelli et al (2012), Winter et al (2013) and Moretti et al (2014), investigating also DON translocation during FCR progress, revealed the presence of this secondary metabolite in wheat heads and in the grains, even when Fusarium was not detected in these parts of the plant.…”

An improved growth medium for enhanced inoculum production of the plant growth-promoting fungus Serendipita indica

“…We optimised a medium for S. indica using commercially available vegetable juice as the main ingredient. Media based on the commercially available vegetable juice V8 have been shown to be useful for growth and sporangia induction of the plant pathogenic fungus Phytophthora [19], and are frequently used for conidia production in different ascomycetes including Fusarium culmorum, Parastagnospora nodorum and Pyrenophora tritici-repentis [23,24].…”

An improved growth medium for enhanced inoculum production of the plant growth-promoting fungusSerendipita indica

“…We optimised a medium for S. indica using commercially available vegetable juice as the main ingredient. Media based on the commercially available vegetable juice V8 have been shown to be useful for growth and sporangia induction of the plant pathogenic fungus Phytophthora [20], and are frequently used for conidia production in different ascomycetes including Fusarium culmorum, Parastagnospora nodorum and Pyrenophora tritici-repentis [24, 25].…”