Influence of plant growth regulators on the interaction between onion plants and white rot pathogen Sclerotium cepivorum Berk.

摘要

The pathogenicity of S. cepivorum isolates (OWR1, OWR2, OWR3, OWR4, OWR5 and OWR6) was initially investigated. All isolates were pathogenic to onion cv. Giza 6 plants, with OWR3 being the most pathogenic. The effects of the plant growth regulators (PGRs) abscisic acid, ATP, gibberellic acid, IAA, kinetin and zeatin (at 25, 50 and 100 ppm) on OWR3-infected onion plants and on sclerotia of this isolate were studied. Two-month-old onion transplants dipped for 48 h in various concentrations of plant growth regulators were inoculated with the isolate before transplanting in the field (Egypt during 1998 and 1999), while sclerotia were soaked in PGRs for 48 h under aseptic conditions. Generally, dipping of onion transplants in PGRs induced resistance toS. cepivorum especially at the highest concentration tested. However, variations in the efficacy of abscisic acid and ATP, and between kinetin and zeatin, were not significant. Gibberellic acid induced the highest resistance to S. cepivorum, i.e. 33.1, 57.9 and 70% reduction at 25, 50 and 100 ppm, respectively. In sclerotial treatments, only gibberellic acid consistently reduced S. cepivorum severity with the increase in its concentration. ABA at 100 ppm, and zeatin at 50 and 100 ppm, also reduced S. cepivorum infection. However, IAA (25 ppm) and ATP (all concentrations) enhanced onion susceptibility to S. cepivorum. Kinetin did not exhibit significant effect toward sclerotia virulence.