Resistant apple cultivars

Relinda cider apple cultivar resistant to scab... 

Other cyclic tetrapeptides have also been isolated by Japanese workers and AM toxins I, II, and III, isolated from Alternaria mail., are extremely toxic to certain plant species (9.10). These are constructed of L- i-hydroxyisovaleric acid, L-alanine, c-amino-acrylic acid and, in AM toxin I, L-6(-amino- -( .-methoxyphenyl)-valeric acid. The phenyl residue in AM toxin II is L-t(-amino-S-phenylvaleric acid, while in AM toxin III, it is L-ol-amino-( .-hydroxyphenyl)valeric acid (Figure 2), All the AM toxins produce leaf spot, or necrosis, in apple but as might he expected slight change in substitution (R-group) on the phenyl ring radically alters the specific activity of the molecule. Both AM toxin I and III induce interveinal necrosis in the "Indo" apple cultivar, which is also highly susceptible to A. mail. at concentrations as low as 0.1 pph within 18 h after treatment. In contrast, the resistant apple cultivar "Jonathan" is only affected by 1 ppm of AM toxin I and 10 ppm of AM toxin III. 

Apple cultivars have different textures due to their internal variability of structure and composition. Some apples resist boiling and do not readily sauce. Others may undergo ready cell separation. This wide range of textural behavior illustrates the complexity due to pectins and other cell-wall materials. Select apple cultivars according to the desired processing qualities. 

Under organic conditions it is preferable to grow varieties that are robust or resistant to scab (see section in Chapter 3 on Apple cultivars). 

Resistant plants, 363,410-11,414. See also Cultivars, resistant Rhagoletes. See Fruit flies RhagoletispomoneUa. See Apple maggots... 

What to do Grow resistant cultivars. Mulch under trees to stop soil from drying out Water trees in dry weather. In winter, cut out infected shoots. In spring, remove infected leaves and shoots. Spray with seaweed extract to promote strong growth. Fungicide spray Sulfur, although it can harm some apples. Check the label before use. 

Pests and disease problems on apple trees are covered in the Apple entry beginning on page 21. Crab apples share many of the same problems, including fire blight, cedar-apple rust, powdery mildew, and apple scab. Ibr-tunately, disease-resistant cultivars are available. Some of the best include Adams , with reddish pink flowers Coral Cascade , with white flowers Prarifire , with purplish red flowers and Professor Sprenger , with white flowers. There are also many other resistant cultivars, so check with your local nursery owner or extension agent to learn about the best ones for your area. 

Prevention is the best control. Rust diseases thrive in moist conditions, so anything you can do to promote leaf drying will limit disease problems. Plant apple trees only if cedars are at least 4 miles away this will reduce the chances of the disease spreading. If you want to grow both cedars and apple trees, plant rust-resistant species or cultivars of both plants. Prune off and destroy galls before late winter. 

Zhang, J., Hausmann, L., Eibach, R., Welter, L.J., Topfer, R., Zyprian, E.M., 2009. A framework map from grapevine V3125 Vitis vinifera Schiava grossa x Riesling )x rootstock cultivar Bomer Vitis riparia x Vitis cinerea) to localize genetic determinants of phylloxera root resistance. Theor. Appl. Genet 119,1039-1051. 

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