Core Rot Development in Red Delicious Apples Is Affected by Susceptibility of the Seed Locule to Alternaria alternata Colonization.

ABSTRACT Alternaria alternata is the causal organism of core rot decay symptoms in susceptible cv. Red Delicious but not in resistant cv. Golden Delicious. The two cultivars did not differ in natural colonization of the style and ovary during the first week after full bloom; colonization of the ovary in the susceptible cultivar subsequently decreased with increasing distance from the calycine tube. By 30 days after full bloom, Alternaria recovery from ovary 1, adjacent to the end of the calycine tube, was 100 and 40% in the susceptible and resistant cultivars, respectively. In the susceptible cultivar, Alternaria recovery decreased from 75 to 20% in ovaries 2, 3, and 4, while there was only minor incidence in the resistant cultivar. Inoculation of the mesoderms of the two cultivars induced similar decay symptoms, but inoculated locules of Red Delicious were more susceptible than those of Golden Delicious. Increased inoculum concentration or isolate virulence enhanced the difference in locule susceptibility between the cultivars. Inoculation on isolated seed locules or on media amended with susceptible locule tissue as a carbon source induced greater transcript levels of several genes than the inoculation on resistant tissue. Endo- and exoglucanase activity levels were higher at pH 4.8 than at 4.2, conditions typical of the mesoderm adjacent to the seed locules of the susceptible and resistant cultivars, respectively. Current results suggest that susceptibility of Red Delicious apples to core rot decay is dependent on the sensitivity to locule colonization and on mesoderm pH, a factor that enhances fungal virulence.

[1]  R. Ben-arie,et al.  Virulence and the Production of Endo‐1,4‐β‐glucanase by Isolates of Alternaria alternata Involved in the Moldy‐core Disease of Apples , 2007 .

[2]  R. Ben-arie,et al.  Sensitivity of Red Delicious Apple Fruit at Various Phenologic Stages to Infection by Alternaria alternata and Moldy-core Control , 2004, European Journal of Plant Pathology.

[3]  D. Treutter.  Biosynthesis of phenolic compounds and its regulation in apple , 2001, Plant Growth Regulation.

[4]  Robert Saftner,et al.  Relationship Between Host Acidification and Virulence of Penicillium spp. on Apple and Citrus Fruit. , 2004, Phytopathology.

[5]  D. Prusky,et al.  Pathogenic fungi: leading or led by ambient pH? , 2003, Molecular plant pathology.

[6]  S. Guyot,et al.  Variability of the polyphenolic composition of cider apple (Malus domestica) fruits and juices. , 2003, Journal of agricultural and food chemistry.

[7]  Y. Cohen,et al.  Control of Moldy-Core Decay in Apple Fruits by β-Aminobutyric Acids and Potassium Phosphites. , 2003, Plant disease.

[8]  A. Dinoor,et al.  Characterization of Alternaria alternata glucanase genes expressed during infection of resistant and susceptible persimmon fruits. , 2002, Molecular plant pathology.

[9]  A. Dinoor,et al.  pH regulates endoglucanase expression and virulence of Alternaria alternata in persimmon fruit. , 2002, Molecular plant-microbe interactions : MPMI.

[10]  Thomas D. Schmittgen,et al.  Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. , 2001, Methods.

[11]  A. Roco,et al.  In vitro biocontrol activity of Trichoderma harzianum on Alternaria alternata in the presence of growth regulators , 2001 .

[12]  M. Yamamoto,et al.  Endopolygalacturonase is essential for citrus black rot caused by Alternaria citri but not brown spot caused by Alternaria alternata. , 2001, Molecular Plant-Microbe Interactions.

[13]  R. Ben-arie,et al.  Resistance of Gibberellin-Treated Persimmon Fruit to Alternaria alternata Arises from the Reduced Ability of the Fungus to Produce Endo-1,4-beta-Glucanase. , 2000, Phytopathology.

[14]  R. Spotts,et al.  Variability in Postharvest Decay Among Apple Cultivars. , 1999, Plant disease.

[15]  M. Akerman,et al.  Effect of hot water brushing, prochloraz treatment and waxing on the incidence of black spot decay caused by Alternaria alternata in mango fruits , 1999 .

[16]  A. Isshiki,et al.  Purification and characterization of an endopolygalacturonase from the rough lemon pathotype ofAlternaria alternata,the cause of citrus brown spot disease☆ , 1997 .

[17]  A. Dinoor,et al.  Purification of pectate lyase produced by Colletotrichum gloeosporioides and its inhibition by epicatechin: a possible factor involved in the resistance of unripe avocado fruits to anthracnose. , 1994, Molecular plant-microbe interactions : MPMI.

[18]  Alan R. Biggs,et al.  Control of Alternaria infection of fruit of apple cultivar Nittany with calcium chloride and fungicides , 1993 .

[19]  A. Quaas,et al.  Release of reducing sugars from Citrus seedlings, leaves and fruits. Effect of treatment with pectinase and cellulase from Alternaria and Trichoderma , 1992 .

[20]  R. Spotts,et al.  Effect of Ozonated Water on Postharvest Pathogens of Pear in Laboratory and Packinghouse Tests , 1992 .

[21]  K. Eriksson,et al.  An assay for selective determination of exo-1,4,-beta-glucanases in a mixture of cellulolytic enzymes. , 1984, Analytical biochemistry.

[22]  M. Ellis,et al.  Colonization of delicious apple fruits by Alternaria spp. and effect of fungicide sprays on moldy-core , 1983 .

[23]  M. Ettlinger,et al.  Nojirimycin and d-glucono-1,5-lactone as inhibitors of carbohydrases , 1971 .

[24]  M. Mandels,et al.  The Production of Cellulases , 1969 .