Table 3.
Pathogen development in Medicago truncatula R108 plants expressing hairpin RNA (hpRNA) for PR10.1, TLP or CHS.
| Colletotrichum trifolii | Erysiphe pisi | Phytophthora medicaginis | |
|---|---|---|---|
| Line | Percentage spores arrested | ng DNA/root (SD) | |
| ABR20 | 68 | 37 | 2.2 (2.8) |
| ABR21 | 75 | 19 | 7.9 (7.1) |
| TLP55 | 69 | 38 | 4.3 (9.8) |
| TLP56 | 73 | 16 | 4.1 (4.9) |
| CHS11 | 22* | 23 | 63.3 (22.2)† |
| R108 | 76 | 22 | 10.8 (10.9) |
| A17 | 69 | 97 | 2.9 (3.4) |
| Vector control | 63 | 34 | 8.1 (7.0) |
The percentage of Colletotrichum trifolii and Erysiphe pisi spores arrested in development (not forming a mycelium) after germination on leaves and the amount of Phytophthora medicaginis DNA in seedling roots of transgenic and control lines were measured.
Plants from each line were inoculated to test the effect of gene down‐regulation on disease resistance. Lines ABR20 and ABR21 contain an RNAi construct for down‐regulation of PR10.1, lines TLP55 and TLP56 contain an RNAi construct for down‐regulation of TLP, and line CHS11 contains an RNAi construct for down‐regulation of CHS. Line R108 and the vector control are resistant to C. trifolii and moderately susceptible to E. pisi and P. medicaginis. Line A17 is resistant to C. trifolii and E. pisi, and moderately susceptible to P. medicaginis. Detached leaflets (n= 24) were spot inoculated with C. trifolii spores, fixed and stained to visualize mycelia by light microscopy at 2 days after inoculation. Whole plants were inoculated with E. pisi conidia and leaflets (n= 36) were stained to visualize mycelia at 2 days after inoculation. The numbers of spores that formed a mycelium or that were arrested in development after germination were counted. Seedlings (n= 10) were inoculated with P. medicaginis mycelium and the amount of pathogen DNA in each seedling root was measured 4 days after inoculation by a quantitative real‐time polymerase chain reaction assay.
Significantly different from the vector control at P= 0.0116. The proportions of arrested spores from each leaflet were square root arcsin transformed and analysed by Student's t‐test. All other transgenic lines were not significantly different from the vector control. No significant differences were observed between vector control and transgenic lines when inoculated with E. pisi.
Significantly different from the vector control at P= 0.0021 by Student's t‐test. All other transgenic lines were not significantly different from the vector control.
CHS, chalcone synthase; SD, standard deviation; TLP, thaumatin‐like protein.