Induction of Resistance in Melon to Didymella bryoniae and Sclerotinia sclerotiorum by Seed Treatments with Acibenzolar‐S‐methyl and Methyl Jasmonate but not with Salicylic Acid

Abstract

The plant resistance activator acibenzolar‐S‐methyl (BTH), the signalling molecules salicylic acid (SA) and methyl jasmonate (MeJA) were tested by seed treatment for their ability to protect melon seedlings from gummy stem blight and white mould disease caused by the soil‐borne fungal pathogens Didymella bryoniae and Sclerotinia sclerotiorum, respectively. Didymella bryoniae infection on melon seedlings was completely suppressed by MeJA treatment. Necrotic lesions akin hypersensitive response occurred on all inoculated seedlings and prevented pathogen diffusion into healthy tissues. Didymella bryoniae infection was restricted following BTH seed treatment as well, although the percentage of necrotic lesions in comparison with the water soaked lesions was significantly lower than that from MeJA‐induced seedlings. BTH protected melon seedlings against S. sclerotiorum by the occurrence of a high percentage of necrotic lesions. A lower level of resistance was also achieved by MeJA seed treatment. The augmented level of resistance of tissues from BTH and MeJA‐treated seeds was associated with rapid increases in the activity of the pathogenesis‐related proteins chitinase and peroxidase. MeJA also determined a rapid and transient accumulation of lipoxygenase. Moreover, BTH and MeJA treatments determined the differential induction of particular de novo synthesized isoenzymes of these proteins. Results indicate that BTH and MeJA applied to melon seeds may activate on seedlings diverse metabolic pathways leading to the enhancement of resistance against distinct pathogens.

Transmission of Plant-Pathogenic Bacteria by Nonhost Seeds without Induction of an Associated Defense Reaction at Emergence

“…campestris and acibenzolar-S-methyl. The induction of defense responses was previously observed for other plant seedlings such as cowpea and melon (6,28). These plant defense responses are specifically induced by bacterial T3SS effectors upon recognition by the corresponding resistance genes (26).…”

Differential Activity of Peroxidase Isozymes in Response to Wounding, Gypsy Moth, and Plant Hormones in Northern Red Oak (Quercus rubra L.)

“…In addition, generalized soluble or wall-bound POD activity increases in other plant species in response to wounding (Birecka and Miller, 1974;Kawaoka et al, 1994), pathogens (Bashan et al, 1987), salicylic acid (Rao et al, 1997), and jasmonates (Thaler et al, 1996;Moore et al, 2003). While JA and insect wounding have been found to elevate total soluble POD activity similarly (Choi et al, 1994;Tamari et al, 1995;Zhang and Baldwin, 1997), this study is among the first to suggest that various peroxidase isozymes may be differentially responsive to JA or other signals (Buzi et al, 2004) and the first to find insectresponsive POD isoforms. Our results also indicate that JA does not elicit POD isozymes in exactly the same manner as does gypsy moth herbivory.…”

The prospect of applying chemical elicitors and plant strengtheners to enhance the biological control of crop pests

“…Control plants were not sprayed at all. In a second experiment, maize seeds were soaked in chemical solutions for 12 h until complete absorption of the liquid [76]. Laminarin treatment was performed using a solution of 20 ml, using a concentration of 0.02% (v/v) in distilled water.…”