Histopathology of Sclerotinia Sclerotiorum Attack on Flower Parts of Helianthus Annuus heads in Tolerant and Susceptible Varieties

Abstract

Sunflower head rot is a major disease caused by Sclerotinia sclerotiorum. Sunflower varieties which are tolerant to the fungus have been developed. The changes occurring in flower parts at different times after inoculation with pathogen ascospores were studied for two sunflower varieties (tolerant HA 302 and susceptible HA 89). In variety HA 302 there was cell collapse, changes in cell wall composition, and an increase in phenolic compounds in the tissues of corolla and style, which prevented the pathogen from advancing. This response was weaker in susceptible variety HA 89, and occurred only in the style, so did not stop the pathogen from developing and reaching the ovary. Phenolic compounds were found in HA 302 corolla and style tissues only when the pathogen was present, constituted an induced response that prevented further development of the fungus. Principal component analysis (PCA) showed that at the beginning of the infection there was no difference in behavior between the two varieties. The difference arose during the final observation times, when in variety HA 89, the pathogen colonized ovary, style and base of filaments and produced noticeable colonization of the corolla.

The chemical inducer, BTH (benzothiadiazole) and root colonization by mycorrhizal fungi (Glomus spp.) trigger resistance against white rot (Sclerotinia sclerotiorum) in sunflower

“…In an earlier work of our research group, autofluorescence and the accumulation of reactive oxygen species (ROS) were also found to be associated with induced resistance in P. halstedii-infected and BTH-treated sunflower plants [3]. Changes in cell wall composition and accumulation of phenolic compound were also reported in sunflower flower parts infected by SS [21]. In addition, accumulation of fluorescent compounds was suggested to be involved in the induction of a localized and systemic resistance by an arbuscular mycorrhiza fungus against Phytophthora parasitica in tomato [7].…”

Monolignol biosynthesis is associated with resistance to Sclerotinia sclerotiorum in Camelina sativa

“…Despite the substantial impact of S. sclerotiorum on agricultural production, the molecular mechanisms of host resistance to this pathogen have received little attention and remain poorly understood. The evidence for a role of lignification in resistance against S. sclerotiorum is mainly of a histochemical nature (Green et al ., 1998; Rodríguez et al ., 2004). In a study comparing transgenic carrots over‐expressing different pathogenesis‐related (PR) proteins for their susceptibility to Botrytis cinerea and S. sclerotiorum , the highest levels of resistance were seen in transgenic lines over‐expressing the peroxidase POC1.…”

Analysis of Differential Transcript Expression Reveals Time-Dependent Leaf Responses to Sclerotinia sclerotiorum in Wild and Cultivated Sunflower

“…An increased supply after induction probably leads to an increased pool of coumaroyl-CoA that is provided to synthesise diverse hydroxycinnamic acids and precursors of lignins, lignans, suberins, coumarins and flavonoids (Hahlbrock and Scheel 1989;Dixon and Paiva 1995). The role of phenolic and hydroxycinnamic acids in HelianthusSclerotinia interaction has been shown previously (Bazzalo et al 1985;Hemery-Tardin et al 1998;Prats et al 2003;Rodriguez et al 2004). Also coumarins have been mentioned to play a crucial role in pathogen defence and resistance to S. sclerotiorum in sunflower (Tal and Robeson 1986;Urdangarin et al 1999;Prats et al 2006).…”