Greenhouse
|
Container.......... |
Bench, pot, or flat deep enough to allow root development |
| Media............... | Sand or soil mixture |
| Temp/Light........ | 24 to 30°C; 16+ hour daylength |
| No. of Plants .... | 35 to 50 per replication |
| No. of Reps....... | 3 replications minimum |
| Other................ | Inoculate with Rhizobium meliloti Dang, encourage vigorous growth |
INOCULUM CULTURE
|
Source.............. |
|
| Storage............. | Inoculated sterile soil cultures or solid PDA medium |
| Temperature....... | 0°C to ambient |
| Storage Life....... | Several years in soil tubes |
INOCULATION PROCEDURE
| Age of Plant...... | 8 to 10 weeks old |
| Type of Inoc....... | Microconidia in suspension |
| Inoc. Culture ..... | Potato or nutrient broth (2 g NaNO3, 1 g KH2PO4, 0.5 g MgSO4-7H2O, 0.5 g KCI, 0.01 g FeSO4-7H2O, 0.5 g yeast extract, and 15 g sucrose per 1 L distilled water); inoculate sterile broth wlth PDA plugs and incubate on a shaker for 4 days at about 21°C |
| Concentration ... | 1.6 X 106 spores per mL or a 1:20 dilution of the shake culture |
| Method ............. | Bare root soak |
| Time of Inoc....... | 20 to 30 min. |
INCUBATION
| Location ........... | Transplant to field |
| Plant Counts .... | Approximately 2 wks after transplanting, count all (alive and dead) plants as the base count for initial stand |
| Culture ............. | Maintain vigorous growth, control insects, clip plants once or twice. |
| Spacing ........... | 0.15 m between plants, 1.0 m between rows. |
| Age at Rating.... | 3 months after transplanting |
RATING
Plants are removed from the field and the tap root
sectioned for rating.
| 0 Resistant ............. | No discoloration in the root |
| 1 Resistant ............. | Small dark strands in the stele |
| 2 Susceptible .......... | Small dark-brown arcs or rings in cross section of the stele |
| 3 Susceptible .......... | Larger dark-brown areas, arcs or rings, or partial dark- brown ring in the outer stele |
| 4 Susceptible .......... | Entire outer stele dark brown, plant alive |
| 5 Susceptible .......... | Dead plant (stand loss) |
CHECK CULTIVARS
| Approximate Expected Resistance (%) | Acceptable Range of Reaction (%) | |
| Resistant | ||
| Agate** | 54 | 45-65 |
| Moapa 69 | 76 | 65-85 |
| Moderately Resistant | ||
| Narragansett | 22 | 15-30 |
| Susceptible | ||
| MNGN-l ** | 4 | 0-8 |
Values for resistant standards are totals of O's and l's.
DISTRIBUTION AND
SEVERITY OF
FUSARIUM WILT
Fusarium wilt, Fusarium oxysporum Schlecht f.
sp. medicaginis (Snyd. & Hans.)
(Click on the map above for a larger version. See
also the KEY)
SOURCE OF INOCULUM AND EXPERTISE
Name ..............Judy A. Thies
Address ...........USDA-ARS
D