Anthracnose Fruit Rot Research Articles

Effectiveness of a Low-volume Spray Technology in the Control of Major Strawberry Diseases in Florida

Florida strawberry production is greatly affected by Botrytis and anthracnose fruit rots (BFR and AFR), caused by Botrytis cinerea and Colletotrichum acutatum, respectively. Fungicide applications are the most effective method for control of both diseases. Traditionally, Florida strawberry growers use sprayers mounted with hydraulic nozzles delivering high flow rates. The objective of this study was to compare the standard hydraulic nozzle (SHN) sprayer with the air-assisted rotary atomizer (AARA). The effects of low volumes on the control of BFR and AFR, the reduction of 25% on fungicide rate, and their operational efficiency were evaluated, and an economic analysis was conducted. Two experiments were conducted (in the 2014-2015 and 2015-2016 seasons) where three treatments were compared: two using the AARA at 25 gal/acre, one of these with 75% of the fungicide rate; and one using the SHN at 100 gal/acre. In the first season, yield, AFR control, and BFR control were similar for all three treatments. In the second, BFR control was similar among all the treatments. However, the AARA treatment had a higher yield than the SHN, with the AARA (75% rate) being more productive. The operational capacity in acres per hour of the AARA was 17% higher than the SHN. Labor and fungicide costs were lower in the AARA treatments. Thus, the technology was shown to be a good fit for Florida growers.Accepted for publication 25 October 2016.

Resistance in Colletotrichum siamense From Peach and Blueberry to Thiophanate-Methyl and Azoxystrobin.

Anthracnose fruit rot was observed in some late-season peach cultivars in South Carolina in the 2012 and 2013 production seasons as well as increased anthracnose leaf spot of blueberry in a commercial operation of the same state in 2012. Single-spore isolates of Colletotrichum siamense were either sensitive or resistant to both thiophanate-methyl and azoxystrobin with the concentration of the fungicide at which fungal development is inhibited by 50% of ≥100 μg/ml. Resistant isolates revealed the E198A mutation in β-tubulin and the G143A mutation in cytochrome b. Nucleotide sequence analysis of the complete CYTB gene from genomic DNA of C. siamense isolates revealed an intronless genotype (CsI) and a genotype revealing two introns (CsII) at amino acid positions 131 and 164. Resistance to thiophanate-methyl or azoxystrobin was not found in isolates of C. fructicola collected from peach fruit. The CYTB gene of isolates of this species was of the CfII genotype or revealed a unique CfIIa genotype. Phylogenetic analysis of C. siamense isolates from different locations and different crops showed that the resistant isolates were genetically closer to each other than to sensitive isolates, suggesting that field resistance to thiophanate-methyl and azoxystrobin fungicides is derived from a common ancestor.

Characterization of Colletotrichum spp. causing anthracnose of bell pepper (Capsicum annuum L.) in Trinidad

Anthracnose fruit rot of pepper (Capsicum spp.) is an economically important disease in many countries worldwide. This study was conducted to identify and characterize the pathogens responsible for anthracnose disease in bell peppers (C. annuum L.) in Trinidad. Seventy-two percent of all isolates were Colletotrichum truncatum and 28% were C. gloeosporioides. Growth rate and conidia dimensions were reliable morphological markers that allowed differentiation between C. gloeosporioides and C. truncatum isolates. Benomyl sensitivity testing also distinguished between isolates of C. gloeosporioides and C. truncatum. C. truncatum was resistant to benomyl at all concentrations tested while C. gloeosporioides sensu lato was sensitive to concentrations above 0.1 μg ml-1 . Pathogenicity tests demonstrated different levels of resistance to anthracnose in various Capsicum genotypes. C. gloeosporioides sensu lato isolates caused significantly greater damage than C. truncatum isolates regardless of pepper cultivar. PCR with taxon- and species-specific primers produced amplicons of expected band sizes for all Colletotrichum species and only for C. gloeosporioides, respectively. Molecular analysis of ITS and β-tubulin sequences positioned C. gloeosporioides sensu lato and C. truncatum isolates from bell pepper into separate species-specific clusters.

First Report of Colletotrichum truncatum Causing Anthracnose of Tomato in China.

Colletotrichum truncatum (syn. C. capsici) is an important plant pathogen that has a wide host range including pepper, eggplant, muskmelon, chickpea, grapes, and many other species of plants (1,2). Anthracnose fruit rot incited by C. coccodes is a prevalent disease in some major tomato (Solanum esculentum) producing regions in China. In October 2012, anthracnose symptoms (circular, sunken lesions with spore masses produced in black acervuli) were observed on ripe tomato fruit in Fuzhou City of Fujian Province, China. Three single-spore isolates (FZ-1, FZ-2, and FZ-3) were derived from fungal cultures isolated from different infected fruits from the same farm. A mycelial plug (5 mm in diameter) from the growing edge of an active colony of each isolate was transferred onto potato dextrose agar (PDA) and incubated at 28°C. Colonies grown on PDA changed from grayish to dark grey with an average colony diameter of 71.8 mm after 7 days. Conidia were falcate and 17.6 to 21.6 × 2.57 to 3.31 μm. Growth rate measured by colony diameter was greater at 25 to 30°C than at other temperatures tested (12, 18, 20, and 37°C). Based upon these morphological and cultural characteristics, the causal agent was identified as C. truncatum (3). To test the three isolates for pathogenicity, detached ripe tomato fruits were each inoculated with 1 μl of a conidial suspension (106 conidia/ml) using either injection or applying a droplet of the spore suspension on the surface of each fruit; the control treatment consisted of fruit that was treated with 1 μl of sterilized water using the two methods of inoculation mentioned above. Five replicate ripe fruits were inoculated with each of the three isolates using each method described above, and incubated in a moist chamber at 25°C. Five ripe fruits were used the negative control treatment for each inoculation method. After 7 days, typical anthracnose symptoms had developed on the inoculated fruit but not on control fruit. To confirm identity of the three isolates, the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA), the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene, a partial sequence of the actin (ACT) gene, and partial histone 3 (HIS3) gene were amplified with ITS1 and ITS4 universal primers, GDF1 and GDR1 primers, ACT-512F and ACT-783R primers, and CYLH3F and CYLH3R primers, respectively (1). The ITS consensus sequence (Accession No. KC460308) of these isolates shared 99% homology with the ITS sequence of C. truncatum in GenBank (AJ301945), and the three other consensus sequences were all 100% homologous with the corresponding sequences of C. truncatum in Genbank (GU228254, GU227960, and GU228058, respectively). The pathogen was re-isolated from the inoculated fruit but not from the control fruit, and the identity of the re-isolates was confirmed to be C. truncatum by morphological features and based on the ITS, GAPDH, ACT, and HIS3 sequences as described above. To our knowledge, this is the first report of C. truncatum causing anthracnose on tomato in China.

Evaluation of epidemics and weather-based fungicide application programmes in controlling anthracnose fruit rot of day-neutral strawberry in outdoor field and protected cultivation systems

Anthracnose fruit rot caused by Colletotrichum acutatum is an economically important disease of strawberry in Ontario. Three years of experiments (2009–2011) were conducted at the University of Guelph’s Cedar Springs Research Station in Blenheim, ON to understand anthracnose fruit rot epidemics in outdoor field and protected production systems and to evaluate different fungicide spray programmes for disease control in day-neutral strawberry. Weather-based fungicide timing programmes were compared with calendar spray programmes in two day-neutral cultivars, ‘Seascape’ and ‘Albion’. Incidence of disease in high-tunnels was very low in all 3 years, even in fungicide non-sprayed plots, indicating that cultivation of day-neutral strawberry in high-tunnels could be an alternative strategy for controlling anthracnose fruit rot with minimal use of fungicides. In outdoor fields, disease incidence was greatly influenced by leaf wetness duration, rainfall and temperature. The use of a weather-based model to determine the timing of fungicide treatments reduced the number of sprays and was as effective as a calendar-based spray at 7-day intervals to reduce the disease and increase marketable fruit yield. Rotating fungicides with different modes of actions (pyraclostrobin, myclobutanil and boscalid + pyraclostrobin) was more effective in reducing disease than regular sprays of captan. The outcomes of this research will be useful to develop decision support tools and select proper fungicides and cultivation systems to manage anthracnose.

First Confirmed Report of Anthracnose Fruit Rot Caused by Colletotrichum gloeosporioides on Common Fig in Korea.

Common fig (Ficus carica L.) was introduced into Korea in the 1890s from Japan and planted in residential gardens for home consumption. Commercial cultivation of the tree did not begin until the 1990s (2). In early August 2012, several dozen unripened fig fruits, cv. Banane, were found damaged by fruit rot in an experimental plot of Jeollabuk-do Agricultural Research and Extension Services, Iksan City, South Korea (GPS coordinates 35°56'38.44″ N, 126°59'37.14″ E). Though infections recurred until late September, infection rates were as low as 1 to 5%. Early symptoms appeared as small, slightly sunken, water-soaked, and circular spots. Lesions increased in size, became more depressed, with a darkened central portion. The darkened areas contained blackish acervuli from which masses of salmon-colored conidia were released in moist weather. A semisoft decay resulted, sometimes causing premature fruit drop. No symptoms were found on leaves. Acervuli were circular to ellipsoid, 50 to 400 μm in diameter. Acervular setae were 2- to 3-septate, dark brown at the base, paler toward the apices, acicular, and up to 120 μm long. Conidia (n = 30) were long obclavate to oblong-elliptical, sometimes fusiform-elliptical, guttulate, hyaline, and 16 to 21 × 4 to 6 μm. These characters were consistent with the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. (4). From an isolate (KACC46943, deposited in the Korean Agricultural Culture Collection), fungal DNA was extracted, and the complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1(5'-TCCGTAGGTGAACCTGCGG-3')/ITS4(5'-TCCTCCGCTTATTGATATGC-3') and sequenced. The resulting 606-bp sequence was deposited in GenBank (KC430919). The sequence showed 100% identity with sequences of C. gloeosporioides (e.g., JX669446, JQ936316, JQ753973). To confirm pathogenicity, inoculum was prepared by harvesting conidia from 3-week-old cultures on potato dextrose agar. A conidial suspension (3 × 105 conidia/ml) was sprayed onto 10 fruits wounded with a fine needle. Ten fruits sprayed with sterile water served as controls. Fruits were placed in moist chambers for 24 h and then kept in plastic containers (25°C and 60 to 80% RH). After 5 days, fruit rot symptoms, identical to those observed in the field, developed on the inoculated fruits, but never on controls. C. gloeosporioides was reisolated from the lesions of inoculated fruits. Anthracnose associated with C. gloeosporioides on common figs has been known from North America, Central America, South America, Australia, New Zealand, South Africa, and Turkey (1). In Korea, anthracnose fruit rot of common figs was recorded in 1928 under the name C. caricae F. Stevens & J.G. Hall, but without fulfillment of Koch's postulates (3). Subsequent to that time, there has been no published finding of the disease in Korea. C. caricae is regarded as synonymous with C. gloeosporioides (4). To our knowledge, this is the first confirmed report of anthracnose fruit rot of common figs caused by C. gloeosporioides in Korea. Anthracnose fruit rot of common figs may cause losses not only for fruit production but also for marketing.

The effect of environmental factors on infection of blueberry fruit by Colletotrichum acutatum

Anthracnose fruit rot of blueberries caused by Colletotrichum acutatum is a serious problem in humid blueberry‐growing regions of North America. In order to develop a disease prediction model, environmental factors that affect mycelial growth, conidial germination, appressorium formation and fruit infection by C. acutatum were investigated. Variables included temperature, wetness duration, wetness interruption and relative humidity. The optimal temperature for mycelial growth was 26°C, and little or no growth was observed at 5 and 35°C. The development of melanized appressoria was studied on Parafilm‐covered glass slides and infection was evaluated in immature and mature blueberry fruits. In all three assays, the optimal temperature for infection was identified as 25°C, and infections increased up to a wetness duration of 48 h. Three‐dimensional Gaussian equations were used to assess the effect of temperature and wetness duration on the development of melanized appressoria (R2 = 0·89) on Parafilm‐covered glass slides and on infection incidence in immature (R2 = 0·86) and mature (R2 = 0·90) blueberry fruits. Interrupted wetness periods of different durations were investigated and models were fitted to the response of melanized appressoria (R2 = 0·95) and infection incidence in immature (R2 = 0·90) and mature (R2 = 0·78) blueberry fruits. Additionally, the development of melanized appressoria and fruit infection incidence were modelled in relation to relative humidity (R2 = 0·99 and 0·97, respectively). Three comprehensive equations were then developed that incorporate the aforementioned variables. The results lay the groundwork for a disease prediction model for anthracnose fruit rot in blueberries.

Characterization and biological activity of flavonoids from ripe fruit of an anthracnose-resistant blueberry cultivar

Anthracnose fruit rot, caused by Colletotrichum acutatum, is among the most important diseases of blueberries. Most cultivars are susceptible but ‘Elliott’ is resistant. Our objective was to identify possible antifungal compounds that play a role in the resistance response. Chemical fractions from freeze-dried, ripe fruit of ‘Elliott’ and a susceptible cultivar (Jersey) were extracted with methanol and ethyl acetate. Extracts were screened on solid media for suppression of microconidiation of C. acutatum. The methanolic extract was fractionated and the soluble methanolic fraction from ‘Elliott’ was the most biologically active. This fraction was dried, dissolved in water, and screened in vivo by pre-treating ripe ‘Jersey’ fruit with 0.5, 1, 2, and 4% solutions (w/v) and subsequently inoculating the fruit with C. acutatum. An 88% reduction in infection incidence was observed after 12 days with the 4% solution. Anthocyanins and other flavonoids were then quantified in fruit of the two cultivars using HPLC-MS. ‘Elliott’ fruit contained more anthocyanins (4.87 mg/g of freeze-dried tissue) than ‘Jersey’ (3.27 mg/g of freeze-dried tissue); however, the same compounds were found in both cultivars. ‘Elliott’ fruit also contained more non-anthocyanin flavonoids (0.18 mg/g of freeze-dried tissue) than ‘Jersey’ (0.12 mg/g of freeze-dried tissue), including two distinctive compounds in ‘Elliott’. The non-anthocyanin flavonoid fractions of both ‘Elliott’ and ‘Jersey’ significantly decreased the growth of C. acutatum in a liquid bioassay but the effect was more pronounced in the ‘Elliott’ fraction. The two distinctive compounds in ‘Elliott’ were further characterized by MS/MS and were identified as quercetin 3-O-rhamnoside and, putatively, syringetin rhamnoside. Additionally, we evaluated ‘Elliott’ and ‘Jersey’ methanolic extracts for their ability to inhibit lipid peroxidation, and the extract obtained from ‘Elliott’ was almost twice as active at inhibiting peroxidation. These results provide new insights into the role of antifungal compounds in the resistance response of ripe ‘Elliott’ blueberries to infection by C. acutatum.

Comparison of Epidemiology of Gray Mold, Anthracnose Fruit Rot, and Powdery Mildew in Day-Neutral Strawberries in Field and High-Tunnel Conditions in Ontario

Anthracnose fruit rot (Colletotrichum acutatum), Botrytis gray mold (Botrytis cinerea), and powdery mildew (Podosphaera aphanis) are major fruit diseases affecting strawberries in Ontario, but the epidemiology and management of these diseases in day-neutral strawberries in high-tunnels plantings are not well understood. Incidences of both Botrytis gray mold (BGM) and anthracnose fruit rot (AFR) were very low in tunnel plots, compared to outdoor plots (5-fold lower BGM incidence and 5–20-fold lower AFR incidence); whereas the incidence of powdery mildew (PM) on berries was higher in the tunnel plots compared to outdoor field plots. BGM incidence was observed in the first two harvest weeks and decreased thereafter in the outdoor plots, where as incidence of BGM was negligible in the tunnel plots. The AFR was first observed in the first week of August and the last week of July in 2009 and 2010, respectively, The epidemics of PM increased after the second week of September in both years. In outdoor field plots, Maestro 80 DF and Nova 40 W or Pristine WG provided good control of BGM and AFR. ‘Seascape’ had significantly lower AFR than ‘Albion’; whereas PM incidence was higher in ‘Seascape’. There were significantly higher (P < 0.01) cumulative marketable fruit numbers (1- to 3-fold higher) and marketable fruit yields (2- to 3.5-fold higher) in tunnel plots than outdoor plots in both years.

Host Defenses Associated with Fruit Infection by Colletotrichum Species with an Emphasis on Anthracnose of Blueberries

Defense mechanisms in fruit against invasion by fungal pathogens fall into several categories, including fruit physiological factors, passive defense responses, and active defense responses. Colletotrichum spp. are common fruit rot pathogens on a variety of crops. The infection strategy of Colletotrichum pp. varies depending upon the host and the tissue type being colonized and range from hemibiotrophy to necrotrophy. Anthracnose fruit rot caused by C. acutatum is the most important postharvest disease of blueberries (Vaccinium corymbosum). In order to better understand host resistance mechanisms in blueberry fruits, the resistant cultivar Elliott was compared with the susceptible cultivar Jersey. Higher levels of hydrogen peroxide and differentially expressed defense-related genes were found in ‘Elliott’ than in ‘Jersey’ fruit after inoculation. Furthermore, higher levels of anthocyanins and flavonols, including two distinctive compounds, were observed in Elliott fruits and two unique flavonols were present in Elliott. Additionally, pH and sugar content were implicated as being involved in host resistance in blueberry fruits. The results from these studies provide a significant contribution to the understanding of the multiple factors that contribute to anthracnose fruit rot resistance in blueberry. Accepted for publication 15 August 2013. Published 25 November 2013.

Strawberry Anthracnose: Progress toward Control through Science

Anthracnose crown rot has been a destructive disease of strawberries in the southeastern U.S. since the 1930s. The causal fungus, C. fragariae, infects all above-ground plant parts; however, disease is most severe when the fungus infects the crown causing crown rot, wilt, and death. Colletotrichum gloeosporioides can also cause crown rot and has been a problem since the late 1970s. The anthracnose fruit rot pathogen, Colletotrichum acutatum, was first reported on strawberry in the U.S. in 1986. Scientific investigations of anthracnose have concentrated on its epidemiology, differences among the three causal Colletotrichum spp., their infection processes, and pathogenicity. Results from these many studies have improved control of this disease.

Novel source of resistance and differential reactions on chilli fruit infected by Colletotrichum capsici

Pre- and post-harvest anthracnose fruit rot is a main disease of chilli (Capsicum spp.). Among Colletotrichum species causing anthracnose, C. capsici is the most common in India. A total of 41 Capsicum genotypes were screened for anthracnose resistance under field conditions. Bhut Jolokia, PBC-380 and IC-383072 were found symptomless and some marginally cultivated lines and other crosses were observed to be resistant. In vitro inoculation of the selected set of genotypes with C. capsici revealed that 9 days after inoculation was appropriate to record observations on disease resistance. Screening the 41 genotypes for resistance to anthracnose under in vitro conditions revealed four symptomless and 11 highly resistant lines. Comparing field and in vitro evaluations, nine lines (BS-35, BS-20, BS-28, Punjab Lal, Bhut Jolokia, Taiwan-2, IC-383072, Pant C-1 and Lankamura Collection) showed consistent resistance in field as well as in vitro to the disease. The study on differential reactions on fruits of 16 genotypes inoculated by the two C. capsici isolates (Ccf-Varanasi and Ccc2-Raichur) clearly showed that these isolates are two different pathotypes. A detailed analysis on prevalent strains in the target region would be needed to initiate resistance breeding. Nevertheless, newly identified resistant sources offer better choices for the ongoing anthracnose resistance breeding program.

Anthracnose Fruit Rot of Strawberry

Anthracnose fruit rot is an important disease for strawberry worldwide. Lesions appear as dark, sunken spots on infected fruit. This revised 4-page fact sheet was written by James C. Mertely and Natalia A. Peres, and published by the UF Department of Plant Pathology, September 2012. PP-207/PP130: Anthracnose Fruit Rot of Strawberry (ufl.edu)

First Report of Anthracnose Fruit Rot of Strawberry Caused by Colletotrichum acutatum in Montenegro.

Strawberries (Fragaria × ananassa) in Montenegro have become an increasingly important economic crop in recent years. During May 2011, severe fruit damage in strawberry cv. Clery was observed in two fields in the Podgorica region. Fruit symptoms were typical for strawberry anthracnose: sunken, dark brown to black circular lesions appeared on maturing fruits. However, no stem, crown, or foliar symptoms were observed. Under wet conditions, orange masses of conidia were produced in acervuli in the center of lesions. Conidia were hyaline, aseptate, cylindrical, with pointed ends, measuring 9.8 to 17.2 (mean 14.3) × 2.5 to 6.1 (mean 4.4) μm. Colonies on potato dextrose agar (PDA) were initially white, then turned gray as conidia formed in orange to salmon pink masses around the center of the culture. Setae or an ascigerous stage were never observed in culture or on the host. Koch's postulates were fulfilled by inoculating ripe and unripe asymptomatic fruits (20 of each, removed from strawberry plants cv. Clery) with the isolated fungus. Fruits were sprayinoculated (106 conidia/ml). An equal number of noninoculated fruits were used as a control. After incubation time of 2 to 3 days at 25°C in a moist chamber, symptoms appeared on inoculated ripe fruits. On unripe fruits, the lesions developed only 3 to 4 days after the inoculation. No symptoms were found on control fruits. The fungus was reisolated from fruits, after which typical morphological characteristics developed in culture as described above. On the basis of the symptoms, the morphological and cultural characteristics of the fungus, and the pathogenicity test, the disease was identified as strawberry anthracnose caused by Colletotrichum acutatum, which is in accordance with previous reports (1,2,3,4). The isolate was submitted to the Centraalbureau voor Schimmelcultures in the Netherlands (CBS 131813). The internal transcribed spacer (ITS) region of the fungal DNA was amplified with ITS1F and ITS4 primers, sequenced, and submitted to NCBI GenBank (Accession No. JQ424934). BLASTn searches of GenBank using the ITS sequence revealed 99% similarity with database sequences of C. acutatum. Since the pathogen was found in the main Montenegrin strawberry production area, it poses a threat to strawberry production in Montenegro. To our knowledge, this is the first report of anthracnose fruit rot of strawberry in Montenegro.

Use of Leaf Wetness and Temperature to Time Fungicide Applications to Control Anthracnose Fruit Rot of Strawberry in Florida.

Anthracnose fruit rot (AFR), caused by Colletotrichum acutatum, is a major disease of strawberry in Florida and is generally controlled by weekly fungicide applications. More than 20 applications may be made during the growing season, most commonly using captan and the quinone-outside inhibitors. Field experiments were conducted for three seasons on a susceptible and a partially resistant cultivar to evaluate the effectiveness of timing fungicide applications for managing AFR based on a previously published model by Wilson and associates that uses leaf wetness duration and temperature to predict fruit infection by C. acutatum under controlled conditions. For most treatments, rules were established where captan was applied when the predicted proportion of fruit infected (INF) from the model exceeded 0.15 and pyraclostrobin was applied when INF exceeded 0.5. For one model-timed treatment where captan and pyraclostrobin were applied before symptoms first appeared in the field, disease control was as good as the treatment where calendar weekly applications were made and the model-timed treatment utilized 47% fewer sprays. In treatments where fungicide application began after symptom appearance, the number of applications was reduced further but disease control was 40% less effective. Model-timed fungicide treatments that included pyraclostrobin gave better control than the treatments using captan alone. The model relating leaf wetness and temperature to predict AFR infection can be used effectively in a disease-forecasting system to time fungicide treatments and greatly reduce the number of applications without loss of disease control or yield.

Bluberry anthracnose, occurrence, harmfulness and control possibilitiesAntraknoza borówki wysokiej, występowanie, szkodliwość i możliwości zwalczania

Summary Anthracnose (called anthracnose fruit rot – ripe rot) is a dangerous disease caused by fungi from the genus Colletotrichum, mainly C. acutatum and C. gleosporioides. Disease symptoms occur on all above ground plant parts, however fruit infection is the most serious. Harmfulness of the disease was particularly high in the season 2011 with hot and humid weather during the flowering, just before and during harvest promoting fruit rotting. The results of monitoring carried out in 2010–2011 showed a considerable difference in cultivar susceptibility. Cultivar Bluetta was the most susceptible to anthracnose, showing over 50% of infected fruits. Medium susceptibility showed the following cultivars: Nelson, Herbert, Toro, Bluerey, Bluecrop, Patriot and Bluegold. Cultivars: Chandler, Darrow, Elliott showed a low level of susceptibility to anthracnose. Other cultivars, Bridget, Sierra, Berkeley and Boniface, were not infected. The control of anthracnose requires several fungicide treatments carried out before flowering of plants to fruit harvest. The highest efficacy in the control of blueberry anthracnose gave cyprodinil + fludioxonil and piraclostrobin + boscalid and biological product Polyversum, which reduced disease severity in 70–80%, while potassium bicarbonate was ineffective.

Evaluation of screening methods and fruit composition in relation to anthracnose fruit rot resistance in blueberries

Anthracnose fruit rot is an important disease of blueberries, and losses are common in humid growing regions. Most commercial cultivars are susceptible and the disease is usually managed with fungicides. However, a few cultivars are considered resistant. The objectives of this study were to: (i) compare different inoculation techniques for anthracnose fruit rot resistance screening, (ii) screen ripe fruit from a range of blueberry cultivars using selected techniques, and (iii) investigate the role of fruit characteristics in anthracnose fruit rot resistance. The following inoculation methods were evaluated on ripe fruit of a susceptible and resistant cultivar using a conidial suspension: spray, droplet, and injection inoculation of whole fruit; and droplet inoculation of the open surface of cut fruit. All whole‐fruit inoculations yielded similar results. Despite the removal of the epidermis, resistance was also expressed in cut fruit but relatively fewer conidia were produced. The cut‐fruit assay required substantially less time and half the amount of fruit to accomplish than whole‐fruit assays. Detached ripe fruit from 24 cultivars in 2008 and 26 cultivars in 2009 were screened for resistance. Results from the cut‐fruit assay correlated best with published resistance ratings. To determine the possible role of fruit characteristics in resistance, fruit pH, titratable acidity, sugar content and firmness were regressed against various fruit rot resistance measures. Fruit rot resistance was positively correlated with sugar content. On defined media, mycelial growth was restricted as sugar concentration increased and pH decreased, suggesting that fruit composition may play a role in the resistance phenotype.

Identification of differentially expressed genes in a resistant versus a susceptible blueberry cultivar after infection by Colletotrichum acutatum.

Anthracnose fruit rot, caused by the fungus Colletotrichum acutatum, is an important disease of blueberry worldwide. The cultivar Elliott is resistant, severely restricting fungal growth and sporulation relative to the susceptible cultivar Jersey. The objectives of this research were as follows: (i) to analyse pre-penetration events in 'Elliott' and 'Jersey' at different stages of fruit development; (ii) to identify putative defence genes in 'Elliott' fruit; and (iii) to monitor the timing of the oxidative burst in both cultivars. Light microscopy revealed no differences in the pre-penetration activities of C. acutatum on the immature fruit of both cultivars. However, at fruit ripening, conidia germinated and formed appressoria more rapidly on 'Jersey' than on 'Elliott' fruit. Using suppression subtractive hybridization, 37 differentially expressed sequence tags (ESTs) were detected in 'Elliott' versus 'Jersey' upon infection. Several of the ESTs had homology to known plant defence genes, such as a class II chitinase, pathogenesis-related protein 10 (PR10) and β-1,3-glucanase. Two putative genes involved in oxidative stress were identified: a metallothionein-like protein and monodehydroascorbate reductase. ESTs of fungal origin were also detected. Many ESTs had no homology to known genes. Using semi-quantitative and quantitative reverse transcription-polymerase chain reaction (RT-PCR), the expression of most of the candidate genes was detected earlier in 'Elliott' than in 'Jersey', some within 24 h post inoculation (hpi). Monitoring of the oxidative burst showed that the overall H(2) O(2) concentration was two to three times higher in 'Elliott' than in 'Jersey' at 24 hpi. The elucidation of the basis of resistance to C. acutatum in blueberry will facilitate the development of new anthracnose fruit rot-resistant cultivars.

Pre- and post-inoculation activity of a protectant and a systemic fungicide for control of anthracnose fruit rot of strawberry under different wetness durations

A protectant fungicide (Captan, a.i. captan) and a systemic fungicide (Switch, a.i. fludioxonil + cyprodinil) were evaluated as pre- and post-inoculation applications for control of anthracnose fruit rot (AFR), caused by Colletotrichum acutatum, under a short (6 or 8 h) or long (18 or 24 h) wetting period. Evaluations were conducted for two seasons in Maryland and for two seasons in Florida. Both Captan and Switch were very effective for control of AFR when applied prior to inoculation, but control was more effective under the shorter wetting period. Switch was as effective when applied 4, 8, or 24 h post-inoculation as when applied before inoculation, but control was better under the short wetting period. Captan was effective when applied 4 or 8 h after inoculation under the short wetting period, but was ineffective at 24 h post-inoculation. Post-inoculation sprays of Captan were ineffective at any time under the long wetting period. The post-infection activity of Switch allows greater flexibility for managing AFR when fungicide applications are scheduled based on weather-based decision-support systems.

‘Florida Elyana’ Strawberry

'Florida Elyana' is the first Florida-bred strawberry cultivar designed for tunnel and greenhouse production. It is a short-day plant and produces flavorful fruit. 'Florida Elyana' produces larger fruit than 'Strawberry Festival', which is the predominant cultivar in Florida and it holds a large market share in Spain, Morocco and Egypt. 'Florida Elyana' originated from a 2000 cross between FL 96-114 and FL 95-200. 'Florida Elyana' is moderately resistant to the two most serious disease problems on strawberry in Florida: Botrytris fruit rot (caused by Botrytis cinerea) and anthracnose fruit rot (caused by Colletotrichum acutatum). 'Florida Elyana' also appears to have resistance to wilts, which are most likely caused by Colletotrichum gloeosporioides [Glomerella cingulata] and Phytophthora spp.