Table II.
Triple response expression in accessions Col and RLD, and in F3 families of the RLD × Col cross that are homozygous at the ISR1 locus
| Accessions/F3 Familiesa | Triple Response
Assayb
|
|||
|---|---|---|---|---|
| 0 μm | 0.5 μm | 1 μm | 5 μm | |
| Col (ISR1/ISR1) | − | + | + | + |
| ISR1/ISR1 fam 1 | − | + | + | + |
| ISR1/ISR1 fam 2 | − | + | + | + |
| ISR1/ISR1 fam 3 | − | + | + | + |
| ISR1/ISR1 fam 4 | − | + | + | + |
| ISR1/ISR1 fam 5 | − | + | + | + |
| RLD (isr/isr1) | − | − | + | + |
| isr/isr1 fam 1 | − | − | +/− | +/− |
| isr/isr1 fam 2 | − | − | + | + |
| isr/isr1 fam 3 | − | − | + | + |
| isr/isr1 fam 4 | − | − | +/− | +/− |
| isr/isr1 fam 5 | − | − | − | +/− |
The F3 families homozygous for the dominant ISR1 alleles of Col are capable of expressing ISR after treatment of the roots with P. fluorescens WCS417r and exhibit relatively high basal resistance against Pst. The F3 families homozygous for the recessive isr1 alleles of RLD fail to express ISR after treatment of the roots with WCS417r and exhibit relatively low levels of basal resistance against Pst (Ton et al., 1999).
Genotypes were assayed for sensitivity to ACC using the triple response assay. Surface-sterilized seeds (50–100) were plated onto MS-agar plates containing different concentrations of ACC. After germination for 2 d at 4°C, seedlings were grown for 3 to 7 d at 20°C in darkness before being examined for triple response expression. +, Consistent triple response in all plants; +/−, inconsistent triple response; −, none of the plants expressed the triple response.