A greenhouse method for screening grapevine seedlings for resistance to anthracnose

Screening for resistance to Elsinoe ampelina (de Bary) Shear, causal agent of grape anthracnose, in grapevine seedlings is commonly conducted by natur al infection over 3 to 4 years in the vineyard. The objective of this resea rch was to develop a greenhouse screening method for selecting grapevine se edlings with resistance to anthracnose, Spores of E. ampelina were obtained from 3- to 4-week-old cultures on potato, dextrose agar, Inoculum concentr ations ranging from 1.3 x 10(3) to 1.3 x 10(7) E. ampelina conidia per mL w ere evaluated and 10(6) conidia/mL was optimum. The time of incubation of s eedlings in a moist chamber after inoculation varied from 24 to 120 hours w ith 24 to hours resulting in good symptom development. Temperatures in the moist chamber from 16 to 32 degrees C were evaluated and the most consisten t results were obtained at 20 to 28 degrees C. The most effective method fo r selecting anthracnose-resistant grape seedlings in the two-to-three true- leaf stage was misting the seedlings with a suspension containing 10(6) con idia/mL in water and placing the inoculated seedlings in a moist chamber at 24 degrees C for 48 hours, followed by 8 days on a greenhouse bench. Resis tant seedlings from the greenhouse screening (those with <10 foliar lesions ) were transplanted into the vineyard and found to be resistant to anthracn ose infection under rainy, humid conditions, This greenhouse procedure for selecting grapevine cultivars and breeding lines with resistance to anthrac nose is accurate, economical,and labor-saving.