Erwinia amylovora can pass through the abscission layer of fruit-bearing twigs and invade apple fruit during fruit maturation

Abstract Anthocyanins are water-soluble pigments responsible for red, pink, purple or blue coloration in the flesh and/or skin of apple fruit. Since consumers prefer anthocyanin rich fruits due to their health benefits, anthocyanin content is an important trait for marketability of apples. Synthesis and accumulation of anthocyanins are controlled by environmental and genetic factors such as transcription factors (TFs). Two-repeat (R2R3) MYB TFs are involved in the regulation of anthocyanin biosynthesis in plants. In this study, the expression of the MdMYBA and MdMYB3 genes encoding R2R3 type MYB TFs were analyzed in apple cultivars with fruit skin color from green to dark red at different growth stages. Fruit samples were collected from “Scarlet Spur”, “Galaxy Gala”, Golden Delicious” “Granny Smith” apple cultivars with dark red, light red, yellow and green fruits, respectively, at four different time periods after full-bloom. Total RNA was isolated from the peel of the collected fruits and the expression of the MdMYBA and MdMYB3 genes was analyzed by real-time RT-PCR. The expression of the MdMYBA gene started to increase at 92 DAFB and thereafter in red-skin apples; however, no expression was observed at any time points in yellow or green-skin apple cultivars. On the other hand, the MdMYB3 gene was expressed in red-skin and yellow-skin apple cultivars starting at 55 DAFB, but no expression was observed in green apple cultivar at any time of fruit maturation. The expression levels of the MdMYBA and MdMYB3 genes varied in apple fruits with different skin coloration indicating that they play a role regulation of the anthocyanin biosynthesis in apple cultivars during fruit maturation.

Download Full-text

Infection frequency of mature apple fruit with Erwinia amylovora deposited on pedicels and its survival in the fruit stored at low temperature

Journal of General Plant Pathology ◽

10.1007/s10327-005-0204-5 ◽

2005 ◽

Vol 71 (4) ◽

pp. 296-301 ◽

Cited By ~ 4

Author(s):

Takanori Tsukamoto ◽

Koji Azegami ◽

Takayuki Matsuura ◽

Tatsuji Ohara ◽

Yasuhiro Inoue ◽

...

Keyword(s):

Low Temperature ◽

Erwinia Amylovora ◽

Apple Fruit ◽

Infection Frequency ◽

Mature Apple

Download Full-text

Relation between Early Drop of Apple Fruit, Ethylene Evolution and Formation of Abscission Layer

Engei Gakkai zasshi ◽

10.2503/jjshs.53.303 ◽

1984 ◽

Vol 53 (3) ◽

pp. 303-307 ◽

Cited By ~ 9

Author(s):

Hirokazu FUKUI ◽

Shigeru IMAKAWA ◽

Tsutomu TAMURA

Keyword(s):

Apple Fruit ◽

Ethylene Evolution ◽

Abscission Layer

Download Full-text

Evaluation of Loop-Mediated Isothermal Amplification for Rapid Detection of Erwinia amylovora on Pear and Apple Fruit Flowers

Plant Disease ◽

10.1094/pdis-09-10-0636 ◽

2011 ◽

Vol 95 (4) ◽

pp. 423-430 ◽

Cited By ~ 29

Author(s):

Todd N. Temple ◽

Kenneth B. Johnson

Keyword(s):

Rapid Detection ◽

Pathogen Detection ◽

Fire Blight ◽

Management Practices ◽

Erwinia Amylovora ◽

Lamp Assay ◽

Apple Fruit ◽

Isothermal Amplification ◽

Loop Mediated Isothermal Amplification ◽

Forecasting Models

Fire blight of pear and apple is frequently an inoculum-limited disease but weather-based forecasting models commonly assume that the pathogen is omnipresent. To improve fire blight risk assessment during flowering, we developed a rapid pathogen detection protocol that uses loop-mediated isothermal amplification (LAMP) to detect DNA of epiphytic Erwinia amylovora on samples of pear and apple flowers. LAMP detected a single flower colonized epiphytically by E. amylovora in a sample of 100 flower clusters (approximately 600 flowers). Samples of 100 flower clusters from orchards (approximately one sample per hectare) were washed and subjected to LAMP, which was completed in 2 h. In three experimental orchards inoculated with E. amylovora, positive LAMP reactions were attained from nine of nine 100-flower cluster samples; pathogen populations in the floral washes averaged 5.2 × 103 CFU per flower as determined by dilution plating. Samples of pear and apple flowers obtained from 60 commercial orchards located in Oregon, Washington, California, and Utah resulted in detection of E. amylovora by LAMP assay from 34 sites, 20 of which developed fire blight. Of samples at early bloom, 10% were positive for epiphytic E. amylovora compared with 28% at petal fall; pathogen density in washes of positive samples averaged 3.2 × 102 CFU per flower. In another 26 orchards, all floral washes were negative for E. amylovora by LAMP and by dilution plating; a light severity of fire blight was observed in 8 of these orchards. Overall, positive detection of epiphytic E. amylovora in commercial orchards by LAMP-based scouting generally occurred at later stages of bloom after heat (risk) units had begun to accumulate, an indication that weather-based forecasting models may be an adequate measure of fire blight risk for many orchardists. Nonetheless, several orchardists communicated that information from the LAMP-based rapid detection protocol resulted in modification of their fire blight management practices.

Download Full-text

Evaluation of Strategies for Fire Blight Control in Organic Pome Fruit Without Antibiotics

Plant Disease ◽

10.1094/pdis-07-12-0638-re ◽

2013 ◽

Vol 97 (3) ◽

pp. 402-409 ◽

Cited By ~ 18

Author(s):

Kenneth B. Johnson ◽

Todd N. Temple

Keyword(s):

Fire Blight ◽

Erwinia Amylovora ◽

Antibiotic Use ◽

Apple Fruit ◽

Pome Fruit ◽

Biological Products ◽

Control Programs ◽

National Organic Program ◽

Antibiotic Control ◽

Fruit Load

Apple and pear produced organically under the U.S. National Organic Program (NOP) standard can be treated with antibiotics for suppression of fire blight caused by Erwinia amylovora. Recent regulatory actions by the NOP, however, have lessened the likelihood of antibiotic use after the 2014 season. In response, western U.S. organic apple and pear stakeholders identified two immediate-need research objectives related to fire blight control: development of effective non-antibiotic control programs based on combinations of registered biological products; and, in apple, integration of these products with lime sulfur, which is sprayed at early bloom to reduce fruit load. In orchard trials in Oregon, increasing the frequency of treatment with biological products improved suppression of floral infection. In apple, fruit load thinning with 2% lime sulfur plus 2% fish oil (LS+FO) at 30 and 70% bloom significantly (P ≤ 0.05) reduced the proportion of blighted flower clusters in four of five orchard trials. Moreover, lime sulfur significantly (P ≤ 0.05) suppressed epiphytic populations of E. amylovora after their establishment on apple flowers. Over four trials, treatment with Aureobasidium pullulans (Blossom Protect) after LS+FO reduced the incidence of fire blight by an average of 92% compared with water only; this level of control was similar to treatment with streptomycin. In three seasons, a spray of a Pantoea agglomerans product after the 70% bloom treatment of LS+FO established the antagonist on a significantly (P ≤ 0.05) higher proportion of flowers compared with a spray of this bacterium before the thinning treatment. Consequently, in apple, biological treatments for fire blight control are not advised until after lime sulfur treatments for fruit load thinning are completed.

Download Full-text