Volume 54 Number 4 Article 41
Year 2000 Month 10
Title: Resistance of Selected Malus Germplasm to Rosellinia nectrix
Authors: S.-B. Lee, K. Ko, and H.S. Aldwinckle
Abstract:
Isolates of Rosellinia necatrix from Korea, Japan, and the United States were used to inoculate
1-year-old seedlings from open pollinated 'Mclntosh' and 4-year-old M.9 apple rootstock plants to test
the isolates' pathogenicity.
The Korean and U.S. isolates were more virulent to both plant materials
than the Japanese isolate.
Three different methods, inserting infected sticks in pots, mixing infested
soil into pots, and transplanting seedlings into infested soil, were evaluated for assaying the resistance
to R. necatri × of Malus sieversii seedlings grown from seed collected in the wild in Kazakhstan.
The
second method gave more equal inoculum pressure and was selected for further tests.
The M. sieversii seed lot, GMAL 3675 [Plant Introduction (PI) 6005464], showed resistance to the Korean isolate.
Among 159 clones of Malus germplasm in the apple core collection, 32 clones gave seedlings which
had slow development of R. necatrix infection or had no necrotic symptoms.
In a second test of this
germplasm with two fold higher inoculum level, among the selected 32 clones, few seedlings of M. ×
domestica 'Ell-24' (PI 589571), M. × domestica 'E31-10' (PI 590072), M. × domestica 'Redspur Delicious' (PI 589255), M. × domestica 'Smith Jonathan' (PI 589845), M. florentina "Skopje P2' (PI
589385), M. micromalus (PI 594096), M. prunifolia 'Naga' (PI 589930), and M. soulardii (PI 589391)
showed necrotic symptoms of infection, indicating that the parent clones may have some resistance to
R. necatrix.
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