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KMID : 0903619920330030283
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Journal of the Korean Society for Horticultural Science
1992 Volume.33 No. 3 p.283 ~ p.298
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Studies on Alternaria Leaf Spot (a. mali Roberts) in Apple Tree (Malus domestica Borkh) : Epiphytotics , Screening Methods and Inheritance of Resistance
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Abstract
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Studies on the factors gorverning resistant mechanism, and screening methods for the breeding of resistant varieties to Alternaria leaf spot caused by Alternaria mall Roberts were carried out in the Horticultural Experiment Station, Suwon, Korea during the period from 1984 to 1989.
1. It was possible to differentiate the varietal resistance by either dropping or spraying inoculation methods, although the infection rates by spraying were in general too low to effectively separate the reactions. Dropping inoculation on artificially injured leaf surface caused infection even in resistant variety, such as ´Jonathan´.
2. Lesions were developed more rapidly under 25∼30℃ than under the temperature conditions of 20∼25℃. Varietal resistance could be detected within 3 days from inoculation in both temperature ranges.
3. Dropping inoculation made on the lower side of leaf surface was more effective than that on the upper side, but no difference was found between the two sides when leaves were artificially injured before the dropping of the inoculum.
4. It was possible to differentiate the varietal resistance of 22 apple cultivars and 3 wild types by dropping inoculation on the lower side of the 4th unfolded leaf from the shoot tip.
5. Resistant breeding materials could be selected by either percent lesion length in hard wood branch which was previously inserted into the potato dextrose agar containing A. mali or number lesions in the first unfolded leaf which was inoculated with the spore suspension of A. mall in the test tubes.
6. There was no consistent relationship between the concentration of total phenols in the apple leaves and the varietal resistances, but the sizes of stomata, the number of trichomes and stomata per unit leaf surface area seemed to be related with the varietal resistance.
7. By adding fresh leaf juice of resistant varieties to agar media, the growth of mycelium mats was inhibited, while no such effect was found when the leaf juice was autoclaved before adding to the media.
8. Analysis of isoperxidase band patterns in the parental clones did not show any specific band associated with the varietal resistance. However, resistant cultivars seemed to have higher peroxidase activities compared to susceptible ones.
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