March, 1995                                                                                      PDF Version

Fusarium Wilt Resistance - Greenhouse/Controlled Environment
Fusarium oxysporum Schlecht f.sp. medicaginis (Weirner) Snyd. & Hans. J.E. Brumrner and S.L. Nygaard

PLANT CULTURE

Container..........

Bench or tub with adequate depth for root development (6-8 inches)
Media............... Soil Mix (1:2:1; Top soil: sand: sphagnum/perlite) adequate lime and fertilizer (0:24:24)
Temp/Light........ 24 to 30C.; 16+ hour daylength
No. of Plants .... 50-60 per replication
No. of Reps....... 4 replications
Other................ Inoculate with Rhizobium meliloti

INOCULUM CULTURE

Source..............

Infected roots
Storage............. CSilica gel crystals or agar cultures
Temperature......   4-10 C
Storage Life....... 1 to 2 years

INOCULATION PROCEDURE

Age of Plant...... 8 weeks old
Type of Inoc...... Microconidia in water suspension
Inoc. Culture...... Potato Dextrose Broth; inoculate sterile broth with PDA plugs and incubate on a shaker for 4 days at 20-24C.
Concentration..... 1 X 106 spores per ml
Method............... Clip and bare root soak
Time of Inoc....... 20 min at 24C or 12 hours at 16C

INCUBATION

Location............. Greenhouse: transplanted into benches or tubs
Temp/Light........ 28 - 32 C; 16 hour daylength
Culture.............. Provide an arid environment to facilitate symptoms. Clip top growth twice at 5-6 week intervals (at bud or bloom) maintain good growth and control insect pests; fertilize (0-24-24) after each clipping
Spacing............. 2.5 cm between plants and 6 cm between rows
Age of Rating..... 12-14 weeks after transplanting

RATING

Plants are removed from benches and cross sections of roots are rated

Resistant.......Symptomless root or discrete dark specks in the stele of the root

Susceptible....Any dark discoloration in root with an arc or ring pattern; severe necrosis of entire root; dead plant

CHECK CULTIVARS

  Approximate Expected Resistance* Acceptable Range (%)
Resistant    
Agate** 45 35-55
Moapa69 70 60-80
Susceptible    
MNGN-1** 4 0-8

*Controlled environment evaluations can be more severe than field evaluations (check varieties may have a lower resistance when compared to field results)

SOURCE OF INOCULUM
AND EXPERTISE

Name..........Landon Rhodes
Address......Dept. Plant Pathology
                  201 Kottmann Hall
                  Ohio State Univ.
                  202I Coffey Road
                  Columbus, OH 43210

REFERENCES

See Fusarium Wilt field protocol In: STCAC

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