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Abstract

Summary 5Disease symptoms and total soluble phenolics content have been analysed in four sunflower (Helianthus annuus L.) lines with different resistance levels (from highly susceptible to resistant) to head rot caused by Sclerotinia sclerotiorum (Lib.) de Bary. 10At the beginning of the flowering stage, capitula were inoculated by spraying with a water suspension of ascospores, and disease symptoms were evaluated from day 6 to day 14 after inoculation. The most susceptible genotypes showed all their ovaries to be necrosed and abundant lesions in corollas, bracts and receptacle. In the resistant line, the ovary and corolla werer only partially necrosed with no symptoms 15 in the bracts or the receptacle.Total soluble phenolics were extracted and quantified from different parts of the capitulum in both inoculated and non-inoculated plants. The amount of phenolic compounds depended on the sunflower line, the time after inoculation, and the 20 tissue. Higher constitutive and induced phenolic content as well as phenylalanine ammonia-lyase activity were present in the most resistant line, these differences being correlated with the absence/presence of disease symptoms.3

Sunflower (Helianthus annuus L.) Plants at Various Growth Stages Subjected to Extraction—Comparison of the Antioxidant Activity and Phenolic Profile

“…The changes in TPC and individual phenolic content during the sunflower growth cycle reported in the present study can be linked with the physiological role of phenolic compounds in plants. In sunflower tissues, caffeoylquinic acids are considered to be precursors of coumarins (e.g., scopoletin, scopolin and ayapin) which, in turn, play a role in biotic and abiotic stress resistance [26,41,42]. Prats et al [42] reported that the total content of soluble phenolics in sunflower capitula was correlated with resistance to Sclerotinia sclerotiorum.…”

“…In sunflower tissues, caffeoylquinic acids are considered to be precursors of coumarins (e.g., scopoletin, scopolin and ayapin) which, in turn, play a role in biotic and abiotic stress resistance [26,41,42]. Prats et al [42] reported that the total content of soluble phenolics in sunflower capitula was correlated with resistance to Sclerotinia sclerotiorum. In turn, Fernandez et al [25] selected caffeoylquinic acids as putative markers of drought stress in sunflower leaves.…”