Download inoculation of potato plants with ralstonia solanacearum

INOCULATION OF POTATO PLANTS WITH RALSTONIA SOLANACEARUM
BY SOIL INFESTATION IN GREENHOUSE
Sylvie Priou, International Potato Center (CIP), Lima, Peru
Apical cuttings of potato plants or seedlings obtained from sprouted tubers are rooted in small pots
Jiffystrips (Jiffy Products Ltd, Shippegan, Canada), containing about 25 g of the substrate Promix Bx
(Premier Brands, INC, Stamford, Canada). This substrate provides a good level of repeatability of the
results as compared to other soil preparations. Plastic pots containing 200 g of substrate may also be used.
A complete fertilizer (20-20-20) is applied at the time of planting. Plants should be transferred to the
greenhouse at least one day before the inoculation. Greenhouse conditions to favor the disease
development are 28±4ºC and 85-90% R.H. Plants are daily irrigated, except one day before being
inoculated. In each pot containing a one-stemmed 20-day-old plant (about 15 cm tall) are poured 25 ml of
bacterial suspension of R. solanacearum at 108 cfu/ml in order to obtain a final concentration of 108 cfu/g
soil (or 100 ml of bacterial suspension at 2x108 cfu/ml are poured in pots containing 200 g soil).
Twenty plants per genotype are inoculated (at least 10). Wilt incidence (e.g. percentage of wilted plants) is
recorded weekly for a month after inoculation. Alternatively, the disease index can be recorded weekly
based on the following scale: 1 = no symptom; 2 = wilt of one leaf; 3 = wilt of up to half the leaves; 4 = wilt
of nearly all leaves; 5 = complete wilt or death.
Symptomless plants are analyzed individually by post-enrichment DAS-ELISA using CIP’s kit for monitoring
latent infection in stems and percentage of infected plants recorded.
Cruza 148 (CIP 720118) should be used as the moderately resistant control variety together with one or
two local susceptible varieties.