Utilization of indigenous crab apples for the management of foliar and soil borne diseases.
The indigenous crab apples distributed through out the Himalayan region constitute different Malus species. These wild apples have been collected from the various parts of the India and evaluated for resistance against foliar and soilborne diseases such as apple scab, powdery mildew, Marssonina blotch, Alternaria leaf spots, white root rot and seedling blight. Different Malus baccata strains have shown different level of resistance against various diseases. Malus baccata Shillong has been found most promising which in addition to desirable horticultural traits possess high level of resistance for powdery mildew (Podosphaera leucotricha), tolerance to white root rot (Dematophora necatrix [Rosellinia necatrix]) and high degree of resistance to woolly aphid (Eriosoma lanigerum). It has shown field resistance to apple scab (Venturia inaequalis) and Marssonina blotch (Marssonina coronaria [Diplocarpon mali]). Similarly, Malus orientalis, M. baccata mandschurica and M. robusta have shown minimum internal bark rotting against seedling blight (Sclerotium rolfsii [Corticium rolfsii]). Further, the shoot and root segments of M. simcoe, M. orientalis and M. baccata have shown least susceptibility to root rot fungus (D. necatrix). These species are being utilized as root stock for raising plants of delicious and spur type varieties of apple suitable for high density plantations.