EVALUATION OF MALUS SIEVERSII SEEDLINGS FROM KAZAKHSTAN FOR DISEASE RESISTANCE AND TIME OF LEAFING

At Dawes Arboretum, Newark, Ohio, U.S. we have under evaluation approximately 900 seedling trees of the wild apple species Malus sieversii. The seeds were collected by U.S. Department of Agriculture (USDA) plant explorers during three collection trips (1993, 1995 and 1996) to central Asia, specifically Kazakhstan, Kyrgyzstan, Uzbekistan, and Tajikistan.
Our seedlings are from collections of 30 mother trees in 1993, 28 mother trees in 1995 and 73 mother trees in 1996 with progeny populations ranging in number from 1-15. We are evaluating this material for time of leafing (known to be related to time of flowering) with the goal of finding late-leafing (i.e. late-spring-blooming) seedlings.
The seedlings ‘Ohio’ acquired were hoped to have special potential for late-leafing (or frost tolerance of blossoms) because: the 1993 collection was made after a frost at bloom, so the apples collected were either from late bloom or frost-escape flowers; the 1995 collection took more than 120 days to break seed dormancy (thought to be related to late bloom) and were collected from the “big apple” area of Kazakhstan; and the 1996 collection took 120 or more days to break seed dormancy.
The best of these seedlings will be used to add new genetic diversity to the Purdue University apple breeding effort in a combined program, the Midwest Apple Improvement Association (http://www.hort.purdue.edu/ newcrop/maia) with goals of high fruit quality, disease resistance and consistent yield.
Based upon greenhouse inoculations, there are at least three Venturia inaequalis (apple scab) resistance types present in the material – “Vf” (A type), already used in the Purdue breeding program, “r” (B type) and “n” (necrotic type). Some seedlings contain multiple genes for scab resistance.
The Dawes site is thus far free of fire blight (Erwinia amylovora) and cedar apple rust (Gymnosporangium juniperi-virginianae) so field evaluation of these diseases has not yet been possible.
Compared to the cultivar standards, 70% of the seedlings leaf out earlier than ‘Delicious’ (early leafing), 25% leaf with current cultivars and 5% leaf out with ‘Rome’ (late leafing). None leaf out later than ‘Rome’. The trees are consistent in relative time of leafing from year to year.

XI Eucarpia Symposium on Fruit Breeding and Genetics

D.D. Miller

apple, spring frost, fire blight, apple scab, cedar apple rust

https://doi.org/10.17660/ActaHortic.2004.663.93