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The effect of sunflower rust (Puccinia helianthi) infection on intercellular β-1,3-glucanase (EC 3.2.1.39) and chitinase (EC 3.2.1.14) activities, phenylalanine ammonia-lyase (EC 3.4.1.5) activity and total salicylic acid content was investigated in relation to disease development in resistant (PhRR3) and susceptible (S37-388) sunflower plants (Helianthus annuus L.). The effect of benzothiadiazole (BTH) treatment on intercellular β-1,3-glucanase activity and disease severity in susceptible plants was also investigated. Rust infection selectively induced increased activity of the pathogenesis-related proteins, β-1,3-glucanase and chitinase, as well as phenylalanine ammonia-lyase activity and total salicylic acid content in the resistant plants. There was an associated increase in the number of aborted substomatal vesicles as well as host cell necrosis in resistant plants. Treatment of susceptible plants with BTH, a functional analogue of salicylic acid, induced intercellular β-1,3-glucanase activity and reduced the susceptibility to rust. [ABSTRACT FROM AUTHOR]

To investigate the role of β-1,3-glucanases (EC 3.2.1.39) and chitinases (EC 3.2.1.14) in the resistance response of wheat (Triticum aestivum L.) to leaf rust (Puccinia recondita f. sp. tritici), their intercellular activities were studied in resistant (Karee/Lr35) and susceptible (Karee) near-isogenic wheat lines under conditions of infection and non-infection. Resistance was associated with high constitutively expressed chitinase activity and induced β-1,3-glucanase activity. At 168 hours post-inoculation several infection sites on Karee/Lr35 displayed necrosis, confirming a hypersensitive response, whereas similar necrotic lesions were observed only for a limited number of infection sites on Karee at that sampling stage. The possible role of chitinases and β-1,3-glucanases in the hypersensitive defence response of wheat to leaf rust is discussed. [ABSTRACT FROM AUTHOR]